C O N S I D E R A T I O N S

C O L O U R S.

First occasionally written, among some other Essays, to a Friend;

and now suffered to come abroad as

E x p e r i m e n t a l H i s t o r y of

C O L O U R S.

HAVING, in convenient places of the following treatise, mentioned the motives that induced me to write it, and the scope I proposed to myself in it, I think it superfluous to entertain the reader now with what he will meet with hereafter. And I should judge it needless, to trouble others, or myself, with any thing of preface; were it not, that I can scarce doubt, but this book will fall into the hands of some readers, who being unacquainted with the difficulty of attempts of this nature, will think it strange that I should publish any thing about colours, without a particular theory of them. But I dare expect, that intelligent and equitable readers will consider on my behalf, that the professed design of this treatise is to deliver things rather historical than dogmatical, and consequently, if I have added divers new speculative considerations and hints which perhaps may afford no despicable assistance towards the framing of a solid and comprehensive hypothesis, I have done at least as much as I promised, or as the nature of my undertaking exacted. But another thing there is, which if it should be objected, I fear I should not be able so easily to answer it; and that is, that in the following treatise (especially in the third part of it) the experiments might have been better marshalled, and some of them delivered in fewer words. For I must confess, that this essay was written to a private friend, and that too by snatches, at several times and places, and (after my manner) in loose sheets, of which I oftentimes had not all by me that I had already written, when I was writing more; so that it needs be no wonder if all the experiments be not ranged to the best advantage, and if some connexions and consecutions of them might easily have been mended: especially since, having carelessly laid by the loose papers, or several years after they were written, when I came to put them together to dispatch them to the press, I found some of those I reckoned upon, to be very unseasonably wanting. And to make any great change in the order of the rest was more than the printer's importunity, and that of my own avocations (and perhaps also considerable sollicitations) would permit. But though some few preambles of the particular experiments might have (perchance) been spared, or shortened, if I had had all my papers under my view at once; yet in the most of those introductory passages, the reader will (I hope) find hints, or advertisements, as well as transitions. If I sometimes seem to insist long upon the circumstances of a trial, I hope I shall be easily excused by those, that both know how nice divers experiments of colours are, and consider, that I was not barely to relate them, but so as to teach a young gentleman to make them. And if I was not sollicitous to make a nicer division of the whole treatise, than into three parts, whereof the one contains some considerations about colours in general; the other exhibits a specimen of an account of particular colours, exemplified in whiteness and blackness; and the third, promiscuous experiments about the remaining colours (especially red) in order to a theory of them: if, I say, I contented myself with this easy division of my discourse, it was perhaps, because I did not think it so necessary to be curious about the method or contrivance of a treatise, wherein I do not pretend to present my reader with a compleat fabric, or so much as model; but only to bring in materials proper for the building. And if I did not well know, how ingenious the curiosity and civility of friends makes them, to persuade men by specious allegations, to gratify their desires; I should have been made to believe by persons very well qualified to judge of matters of this nature, that the following experiments will not need the addition of accurate method and speculative notions to procure acceptance for the treatise that contains them. For it hath been represented, that in most of them, as the novelty will make them surprizing, and the quickness of performance keep them from being tedious; so the sensible changes, that are effected by them, are so manifest, so great, and so sudden, that scarce any will be displeased to see them, and those that are any thing curious will scarce be able to see them, without finding themselves excited to make reflections upon them. But though with me, who love to measure physical things by their use, not their strangeness, or prettiness, the partiality of others prevails not to make me over-value these, or look upon them in themselves as other than trifle; yet I confess, that ever since I did divers years ago show some of them to a learned company of Virtuosi, so many persons of differing conditions, and even sexes, have been curious to see them, and pleased not to dislike them, that I cannot despair, but that by complying with those that urge the publication of them, I may both gratify and excite the curious, and lay perhaps a foundation, whereon either others or myself may in time superstruct a substantial theory of colours. And if Aristotle, after his master Plato, have rightly observed admiration to be the parent of philosophy, the wonder, some of these-trifles have been wont to produce in all sorts of beholders, and the access they have sometimes gained even to the closets of ladies, seem to promise, that since the subject is so pleasing, that the speculation appears as delightful as difficult, of such easy and recreative experiments, which require but little time, or charge, or trouble in the making, and when made are sensible and surprizing enough, may contribute more than others (far more important, but as much more difficult) to recommend those parts of learning (chymistry and corpuscular philosophy) by which they have been produced, and to which they give testimony even to such kind of persons, as value a pretty trick more than a true notion, and would scarce admit philosophy, if it approached them in another dress. Without the strangeness or endearments of pleasantness to recommend it, I know, that I do but ill consult my own advantage in the consenting to the publication of the following treatis: for those things, which, whilst men knew not how they were performed, appeared so strange, will, when the way of making them, and the grounds on which I devised them, shall be public, quickly lose all, that their being rarities, and their being thought mysteries, contributed to recommend them. But it is fitter for mountebanks than naturalists to desire to have their discoveries rather admired than understood; and for my part I had much rather deserve the thanks of the ingenious, than enjoy the applause of the ignorant. And if I can so far contribute to the discovery of the nature of colours, as to help the curious to it, I shall have reached my end, and saved myself some labour, which else I may chance to be tempted to undergo in prosecuting that subject, and adding to this treatise, which I therefore call a history, because it chiefly contains matters of fact, and which history the title declares me to look upon but as begun. Because though that above a hundred, not to say a hundred and fifty experiments (some loose, and others interwoven amongst the discourses themselves) may suffice to give a beginning to a history not hitherto, that I know, begun by any; yet the subject is so fruitful and so worthy, that those, who are curious of these matters, will be far more wanting to themselves than I can suspect if what I now publish prove any more than a beginning. For, as I hope my endeavours may afford them some a assistance towards this work, so those endeavours are too much unfinished to give them any discouragement, as if there were little left for others to do towards the history of colours.

FOR, (first) I have been willing to leave unmentioned the most part of those phænomena of colours, that nature presents us of her own accord (that is, without being guided or over-ruled by man;) such as the different colours, that several sorts of fruits pass through before they are perfectly ripe, and those that appear upon the fading of flowers and leaves, and the putrefaction (and its several degrees) of fruits, &c. together with a thousand other obvious instances of the changes of colours. Nor have I much meddled with those familiar phænomena, wherein man is not an idle spectator; such as the greenness produced by salt in beef much powdered, and the redness produced in the shells of lobsters upon the boiling of those fishes: for I was willing to leave the gathering of observations to those, that have not the opportunity to make experiments. And for the same reasons, among others, I did purposely omit the lucriferous practice of tradesmen about colours; as the ways of making pigments, of blanching wax, of dying scarlet, &c. though to divers of them I be not a stranger and of some I have myself made trial.

NEXT I did purposely pass by divers experiments of other writers that I had made trial of (and that not without registering some of their events) unless I could some way or other improve them; because I wanted leisure to insert them, and had thoughts of prosecuting the work once begun, of laying together those I had examined by themselves, in case of my not being prevented by others diligence. So that there remains not a little, among the things that are already published, to employ those, that have a mind to exercise themselves in repeating and examining them. And I will not undertake, that none the things delivered, even in this treatise, though never so faithfully set down, may not prove to be thus far of this sort, as to afford the curious somewhat to add about them. For I remember, that I have somewhere in the book itself acknowledged, that having written it by snatches, partly in the country and partly at unseasonable times of the year, when the want of fit instruments, and of a competent variety of flowers, salts, pigments, and other materials, made me leave some of the following experiments (especially those about emphatical colours) far more unfinished than they should have been, if it had been as easy for me to supply what was wanting to compleat them, as to discern. Thirdly, to avoid discouraging the young gentleman I call Pyrophilus, whom the less familiar and more laborious operations of chymistry would probably have frighted, I purposely declined, in what I writ to him, the setting down any number of such chymical experiments, as by being very elaborate or tedious, would either require much skill, or exercise his patience. And yet that this sort of experiments is exceedingly numerous, and might more than a little enrich the history of colours, those that are versed in chymical processes will, I presume, easily allow me.

AND (lastly) for as much as I have occasion more than once in my several writings to treat either purposely or incidentally of matters relating to colours, I did not, perhaps, conceive myself obliged to deliver in one treatise all that I would say concerning that subject.

BUT to conclude, by summing up what I would say concerning what I have, and what I have not done, in the following papers; I shall not (on the one side) deny, that considering, that I pretended not to write an accurate treatise of colours, but an occasional essay to acquaint a private friend with what then occurred to me of the things I had thought or tried concerning them; I might presume I did enough for once, if I did clearly and faithfully set down, though not all the experiments I could, yet at least such a variety of them, that an attentive reader, that shall consider the grounds on which they have been made, and the hints that are purposely (though dispersedly) couched in them, may easily compound them, and otherwise vary them, so as very much to increase their number. And yet (on the other side) I am so sensible both of how much I have, either out of necessity or choice, lest undone, and of the fruitfulness of the subject I have begun to handle; that though I had performed far more than it is like many readers will judge I have, I should yet be very free to let them apply to my attempts that of Seneca, where having spoken of the study of nature's mysteries, and particularly of the cause of earthquakes, he subjoins; Nulla res consmmata est dum incipit. Nec in hac tantum re omnium maxima ac involutissima, in qua etiam cum multum actum erit, omnis etas, quod agat, inveniet; sed in omni alio negotio, lenge semper a perfecto suere principia.

L. Annaei Senecae Natur. Quaest. 1. 6.c. 5-

HERE is presented to thy view one of the abstrusest as well as the genteelest subjects of natural philosophy, the Experimental History of Colours, which, though the noble author be pleased to think but begun, yet I must take leave to say, that I think it so well begun, that the work is more than half dispatched. Concerning which I cannot but give this advertisement to the reader, that I have heard the author express himself, that it would not surprize him, if it should happen to be objected, that some of these experiments have been already published, partly by chymists, and partly by two or three very fresh writers upon other subjects. And though the number of these experiments be but very small, and though they be none of the considerablest, yet it may on this occasion be further represented, that it is easy for our author to name several men (of whose number I can truly name myself) who remember either their having seen him make, or their having read his accounts of the experiments delivered in the following tract several years since, and long before the publication of the books, wherein they are mentioned. Nay, in divers passages (where he could do it without any great inconvenience) he hath struck out experiments, which he had tried many years ago, because he since found them divulged by persons, from whom he had not the least hint of them. Which yet is not touched, with design to reflect upon any ingenious man, as if he were a plagiary: for, though our generous author were not reserved enough in shewing his experiments to those that expressed a curiosity to see them (amongst whom a very learned man hath been pleased publickly to acknowledge it several years *;) yet the same thing may be well enough lighted on by persons, that know nothing of one another. And especially chymical laboratories may many times afford the same phenomenon, about colours, to several persons, at the same or differing times. And as for the few phænomena mentioned in the same chymical writers, as well as in the following treatise, our author hath given an account, why he did not decline rejecting them in the annotations upon the 47th experiment of the third part. Not here to mention, what lie elsewhere saith, to shew what use may justifiably made of experiments not of his own devising by a writer of natural history, if, what he employs of other men’s, be well examined or verified by himself.

IN the mean time, this treatise is such, that there needs no other invitation to peruse it, but that it is composed by one of the deepest and most indefatigable searchers of nature, which, I think the world, as far as I know it, affords. For mine own part, I feel a secret joy within me, to see such beginnings upon such themes, it being demonstratively true, mota facilius moveri; which causeth me to entertain strong hopes, that this illustrious virtuoso and restless inquirer into nature's secrets will not stop here, but go on and prosper in the disquisition of the other principal colours, green, red, and yellow. The reasoning faculty set once afloat will be carried on, and that with ease; especially, when the productions thereof meet, as they do here, with so greedy an entertainment at home and abroad. I am confident, that the ROYAL SOCIETY, lately constituted by his most Excellent Majesty for improving Natural Knowledge will judge it their interest to exhort our author to the prosecution of this argument; considering, how much it is their design and business to accumulate a good stock of such accurate observations and experiments, as may afford them and their offspring genuine matter to raise a masculine philosophy upon, whereby the mind of man may be ennobled with the knowledge of solid truths, and the life of man benefited with ampler accommodations, than it hath been hitherto.

OUR great author, one of the pillars of that illustrious corporation, is constantly furnishing large symbolas to this work; and is now fallen, as you see, upon so comprehensive and important a theme, as will, if insisted on and compleated, prove one of the considerablest pieces of that structure. To which if he shall please to add his treatise of heat and flame, as he is ready to publish his experimental accounts of cold, I esteem, the world will be obliged to him for having shewed them both the right and left-hand of nature, and the operations thereof.

THE considering reader will by this very treatise see abundant cause to sollicit the author for more. Sure I am, that whatever of the productions of his ingeny comes into foreign parts (where I am happy in the acquaintance of many intelligent friends) is highly valued; and to my knowledge, there are those among the French, that have lately begun to learn English, on purpose to enable themselves to read his books, being impatient of their traduction into Latin. If I durst say all I know of the elogies received by me from abroad concerning him, I should perhaps make this preamble too prolix, and certainly offend the modesty of our author.

WHEREFORE I shall leave this, and conclude with desiring the reader, that if he meet with other faults besides those that the Errata take notice of (as I believe he may) he will please to consider both the weakness of the author's eyes for not reviewing, and the manifold avocations of the publisher for not doing his part; who taketh his leave with inviting those, that have also considered this nice subject experimentally, to follow the example of our noble author, and impart such and the like performances to the now very inquisitive world. Farewel.

H. O.

EXPERIMENTAL HISTORY

O F

C O L O U R S

B E G U N.

THE FIRST PART.

C H A P. 1.

1. I HAVE seen you so passionately addicted, Pyrophilus, to the delightful art of limning and painting, that I cannot but think myself obliged to acquaint you with some of those things that have occurred to me concerning the changes of colours. And I may expect that I shall as well serve the Virtuosi in general, as gratify you in particular, by furnishing a person, who, I hope, will both improve my communications, and communicate his improvements, with such experiments and observations as may both invite you to enquire seriously into the nature of colours, and assist you in the investigation of it. This being the principal scope of the following tract, I should do that which might prevent my own design, if I should here attempt to deliver you an accurate and particular theory of colours for that were to present you with what I desire to receive from you; and, as far as in me lay, to make that study needless, to which I would engage you.

2. WHEREFORE my present work shall be but to divert and recreate, as well as excite you by the delivery of matters of fact, such as you may for the most part try with much ease, and possibly not without some delight. And lest you should expect any thing of elaborate or methodical in what you will meet with here, I must confess to you before-hand, that the seasons I was wont to chuse to devise and try experiments about colours, were those days, wherein having taken physic, and finding myself as unfit to speculate, as unwilling to be altogether idle, I chose this diversion as a kind of mean betwixt the one and the other. And I have the less scrupled to set down the following experiments, as some of them came to my mind, and as the notes wherein I had set down the rest, occurred to my hands; that by declining a methodical way of delivering them, I might leave you and myself the greater liberty and convenience to add to them, and transpose them as shall appear expedient.

3. YEA, that you may not think me too reserved, or look upon an inquiry made up of mere narratives, as somewhat jejune, I am content to premise a few considerations, that now offer themselves to my thoughts, which relate in a more general way. either to the nature of colours, or to the study of it. And I shall insert an essay, as well speculative as historical, of the nature of whiteness and blackness, that you may have a specimen of the history of colours, I have sometimes had thoughts of, and if you dislike not the method I have made use of, I hope you, and some of the Virtuosi your friends, may be thereby invited to go thorough with red, blue, yellow, and the rest of the particular colours, as I have done with white and black, but with far more sagacity and success. And if I can invite ingenious men to undertake such tasks, I doubt not but the curious will quickly obtain a better account of colours, than as yet we have, since in our method the theorical part of the inquiry being attended, and as it were interwoven with the historical conjectures, the philosophy of colours will be promoted by the indisputable experiments.

1. To come then in the first place to our more general considerations, I shall begin with saying something as to the importance of examining the colours of bodies. For there are some, especially chymists, who think that a considerable diversity of colours does constantly argue an equal diversity of nature, in the bodies wherein it is conspicuous; but I confess I am not altogether of their mind: for not to mention changeable taffaties, the blue and golden necks of pigeons, and divers water-fowl, rainbows natural and artificial, and other bodies, whose colours the philosophers have been pleased to call not real, but apparent and fantastical; not to insist on these, I say (for fear of needlessly engaging in a controversy) we see in parrots, goldfinches, and divers other birds, not only that the contiguous feathers which are probably as near in properties as place, are some of them red, and others white, some of them blue, and others yellow, &c. but that in the several parts of the self-same feather there may often be seen the greatest disparity of colours. And so in the leaves of tulips, july-flowers, and some other vegetables, the several leaves, and even the several parts of the same leaf, although no difference have been observed in their other properties, are frequently found painted with very different colours. And such a variety we have much more admired in that lovely plant which is commonly, and not unjustly called the Marvel of Peru; for of divers scores of fine flowers, which in its season that gaudy plant does almost daily produce, I have scarce taken notice of any two that were dyed perfectly alike. But though, Pyro, such things as these, among others, keep me from daring to affirm that the diversity and change of colours does always argue any great difference or alteration betwixt, or in the bodies, wherein it is to be discerned; yet that oftentimes the alteration of colours does signify considerable alterations in the disposition of parts of bodies, may appear in the extraction of tinctures, and divers other chymical operations, wherein the change of colours is the chief, and sometimes the only thing, by which the artist regulates his proceeding; and is taught to know when 'tis seasonable for him to leave off. Instances of this sort are more obvious in divers sorts of fruits, as cherries, plums, &c. wherein, according as the vegetable sap is sweetened, or otherwise ripened, by passing from one degree to another of maturation, the external part of the fruit passes likewise from one to another colour. But one of the noblest instances I have met with of this kind, is not so obvious; and that is the way of tempering steel to make gravers, drills, springs, and other mechanical instruments, which we have divers times both made artificers practise in our presence, and tried ourselves after the following manner. First, the slender steel to be tempered is to be hardened by heating as much of it as is requisite among glowing coals, till it be glowing hot, but it must not be quenched as soon as it is taken from the fire (for that would make it too brittle, and spoil it) but must be held over a bason of water, till it descend from a white heat to a red one, which as soon as ever you perceive, you must immediately quench as much as you desire to harden in the cold water. The steel thus hardened will, if it be good, look somewhat white, and must be made bright at the end, that its change of colours may be there conspicuous; and then holding it so in the flame of a candle, that the bright end may be, for about half an inch or more, out of the flame, that the smoak do not stain or fully the brightness of it, you shall after a while see that clean end, which is almost contiguous to the flame, pass very nimbly from one colour to another, as from a brighter yellow, to a deeper and reddish yellow, which artificers call a sanguine; and from that to a fainter first, and then a deeper blue. And to bring home this experiment to our present purpose, it is found by daily experience, that each of these succeeding colours argue such a change made in the texture of the steel, that if it be taken from the flame, and immediately quenched in the tallow (whereby it is settled in whatever temper it had before) when it is yellow, it is of such a hardness as makes it fit for gravers, drills, and such like tools; but if it be kept a few minutes longer in the flame till it grow blue, it becomes much softer, and unfit to make gravers for metals, but fit to make springs for watches, and such like instruments, which are therefore commonly of that colour: and if the steel be kept in the flame, after this deep blue hath disclosed itself, it will grow so soft, as to need to be new hardened again, before it can be brought to a temper fit for drills or penknives. And I confess, Pyro, I have taken much pleasure to see the colours run along from the parts of the steel contiguous to the flame, to the end of the instrument, and succeed one another so fast, that if a man be not vigilant, to thrust the steel into the tallow at the very nick of time, at which it has attained its due colour, he shall miss of giving his tool the right temper. But because the flame of a candle is offensive to my weak eyes, and because it is apt to either black or sully the contiguous part of the steel which is held in it, and thereby hinder the change of colours from being so long and clearly discerned, I have sometimes made this experiment by laying the steel to be tempered upon a heated bar of iron, which we find also, to be employed by some artificers in the tempering of such great instruments, as are too big to be soon heated sufficiently by the flame of a candle. And you may easily satisfy yourself, Pyro, of the differing hardness and toughness, which is ascribed to steel tempered at different colours, if you break but some slender wires of steel so tempered, and observe how they differ in brittleness, and if with a file you also make trial of their various degrees of hardness.

2. BUT, Pyrophilus, I must not at present any further prosecute the consideration of the importance of experiments about colours, not only because you will in the following papers find some instances, that would here be presented you out of their due place, of the use that may be made of such experiments, in discovering in divers bodies what kind the salt is, that is predominant in them; but also because a speculative Naturalist might justly enough allege, that as light is so pleasing an object, as to be well worth our contemplation, though it discovered to us nothing but itself; so modified light, called colour, were worth our contemplation, though by understanding its nature we should be taught nothing else. And however, I need not make either you or myself excuses for entertaining you on the subject I am now about to treat of; since the pleasure Pyro takes in mixing and laying on of colours, will I presume keep him, and will (I am sure) keep me from thinking it troublesome to set down, especially after the tedious processies (about other matters) wherewith I fear I may have tired him, some easy, and not unpleasant experiments relating to that subject.

3. BUT, before we descend to the more particular considerations we are to present you concerning colours, I presume it will be seasonable to propose at the very entrance a distinction; the ignorance or neglect of which, seems to me to have frequently enough occasioned either mistakes or confusion in the writings of divers modern philosophers. For colour may be considered, either as it is a quality residing in, the body that is said to be coloured, or to modify the light after such or such a manner; or else as the light itself, which so modified, strikes upon the organ of sight, and so cause that sensation which we call colour: and that this latter may be looked upon as the more proper, though not the usual acceptation of the word colour, will be made probable by divers passages in the ensuing part of our discourse. And indeed it is the light itself, which after a certain manner, either mingled with shades or some other ways troubled, strikes our eyes, that does more immediately produce that motion in the organ, upon whose account men say they see such or such a colour in the object: yet, because there is in the body that is said to be coloured, a certain disposition of the superficial particles, whereby it sends the light reflected, or refracted, to our eyes thus and thus altered, and not otherwise, it may also in some sense be said, that colour depends upon the visible body; and therefore we shall not be against that way of speaking of colours, that is most used among the modern Naturalists, provided we be allowed to have recourse, when occasion shall require, to the premised distinction, and to take the more immediate cause of colour to be the modified light itself, as it affects the sensory; though the disposition also of the coloured body, as that modifies the light, may be called by that name metonymically (to borrow a school-term) or efficiently, that is, in regard of its turning the light, that rebounds from it, or passes through it, into this or that particular colour.

4. I KNOW not whether I may not on this occasion add, that colour is so far from being an inherent quality of the object in the sense that is wont to be declared by the schools, or even in the sense of some modern Atomists, that, if we consider the matter more attentively, we shall see cause to suspect, if not to conclude, that though light do more immediately affect the organ of sight, than do the bodies that send it thither, yet light itself produces the sensation of a colour, but as it produces such a determinate kind of local motion in some part of the brain; which, though it happen most commonly from the motion whereinto the slender string of the retina are put, by the appulse of light; yet if the like motion happen to be produced by any other cause, wherein the light concurs not at all, a man shall think he sees the same colour. For proof of this, I might put you in mind, that it is usual for dreaming men to think they see the images that appear to them in their sleep, adorned some with this, and some with that lively colour, whilst yet, both the curtains of their bed, and those of their eyes, are close drawn. And I might add the confidence with which distracted persons do oftentimes, when they are awake, think they see black fiends in places, where there is no black object in sight without them. But I will rather observe, that not only when a man receives a great stroke upon his eye, or a very great one upon some other part of his head, he is wont to see, as it were, flashes of lightning, and little vivid, but vanishing flames, though perhaps his eyes be shut; but the like apparitions may happen, when the motion proceeds not from something without, but from something within the body, provided the unwonted fumes that wander up and down in the head, or the propagated concussion of any internal part in the body, do cause, about the inward extremities of the optic nerve, such a motion as is wont to be there produced, when the stroke of the light upon the retina makes us conclude, that we see either light or such and such a colour. This the most ingenious Des Cartes hath very well observed; but because he seems not to have exemplified it by any unobvious or peculiar observation, I shall endeavour to illustrate this doctrine by a few instances.

5. AND first, I remember, that having, through God's goodness, been free for several years from troublesome coughs, being afterwards, by an accident, suddenly cast into a violent one, I did often when I was awaked in the night by my distempers, observe, that upon coughing strongly, it would seem to me, that I saw very vivid, but immediately disappearing flames; which I took particular notice of, because of the conjecture I am now mentioning.

6. AN excellent and very discreet person, very near allied both to you and me, was relating to me, that some time since, whilst she was talking with some other ladies, upon a sudden, all the objects she looked upon appeared to her dyed with unusual colours, some of one kind, and some of another, but all so bright and vivid, that she should have been as much delighted, as surprized with them; but that finding the apparition to continue, she feared it portended some very great alteration as to her health: and indeed, the day after she was assaulted with such violence by hysterical and hypocondrical distempers, as both made her rave for some days, and gave her, during that time, a bastard palsy.

7. BEING awhile since in a town, where the plague had made great havock, and inquiring of an ingenious man, that was so bold, as without much scruple to visit those that were sick of it, about the odd symptoms of a disease that had swept away so many there; he told me, among other things, that he was able to tell divers patients, to whom he was called, before they took their beds, or had any evident symptoms of the plague, that they were indeed infested, upon peculiar observations, that being asked, they would tell him that the neighbouring objects, and particularly his clothes, appeared to them beautified with most glorious colours, like those of the rainbow, oftentimes succeeding one another: and this he affirmed to be one of the most usual, as well as the most early symptoms, by which this odd pestilence disclosed itself, And when I asked how long the patients were wont to be thus affected, he answered, that it was most commonly for about a day; and when I further inquired whether or no vomits, which in that pestilence were usually given, did not remove this symptom (for some used the taking of a vomit, when they came ashore, to cure themselves of the obstinate and troublesome giddiness caused by the motion of the ship) he replied, that generally, upon the evacuation made by the vomit, that strange apparition of colours ceased, though the other symptoms were not so soon abated; yet he added (to take notice of that upon the by, because the observation may perchance do good) that an excellent physician, in whose company he was wont to visit the sick, did give to almost all those to whom he was called, in the beginning, before nature was much weakened, a pretty odd vomit, consisting of eight or ten drachms of infusion of Crocus Metallorum, and about half a drachm, or much more, of white vitriol, with such success, that scarce one of ten to whom it was seasonably administred, miscarried.

8. BUT to return to the consideration of colours: as an apparition of them may be produced by motions from within, without the assistance of an outward object; so I have observed, that it is sometimes possible that the colour that would otherwise be produced by an outward object, may be changed by some motion, or new texture already already produced in the sensory, as long as that unusual motion, or new disposition lasts; for I have divers times tried, that after I have through a telescope looked upon the sun, though thorough a thick, red, or blue glass, to make its splendor supportable to the eye, the impression upon the retina would be not only so vivid, but so permanent, that if afterwards I turned my eye towards a flame, it would appear to me of a colour very differing from its usual one. And if I did divers times successively shut and open the same eye, I should see the adventitious colour (if I may so call it) changed or impaired by degrees, till at length (for this unusual motion of the eye would not presently cease) the flame would appear to me of the same hue that it did to other beholders. A not unlike effect I found by looking upon the moon, when she was near full, thorough an excellent telescope, without coloured glass to screen my eye with: but that which I desire may be taken notice of, because we may elsewhere have occasion to reflect upon it, and because it seems not agreeable to what Anatomists and optical writers deliver, touching the relation of the two eyes to each other, is this circumstance; that though my right eye, with which I looked thorough the telescope, were thus affected by the over-strong impression of the light, yet when the flame of a candle, or some other bright object appeared to me of a very unusual colour, whilst looked upon with the discomposed eye, or (though not so notably) with both eyes at once; yet if I shut that eye, and looked upon the same object with the other, it would appear with no other than its usual colour, though if I again opened, and made us of the dazzled eye, the vivid adventitious colour would again appear. And on this occasion I must not pretermit an observation which may persuade us, that an over-vehement stroke upon the sensory, especially if it be naturally of a weak constitution, may make a more lasting impression than one would imagine; which impression may in some cases, as it were, mingle with, and vitiate the action of vivid objects for a long time after.

FOR I know a lady of unquestionable veracity, who having lately, by a desperate fall, received several hurts, and particularly a considerable one upon a part of her face near her eye, had her sight so troubled and disordered, that, as she hath more than once related to me, not only when the next morning one of her servants came to her bed-side, to ask how she did, his clothes appeared adorned with such variety of dazzling colours, that she was fain presently to command him to withdraw; but the images in her hangings did, for many days after, appear to her, if the room were not extraordinarily darkened, embellished with several offensively vivid colours, which no body else could see in them. And when I enquired whether or no white objects did not appear to her adorned with more luminous colours than others, and whether she saw not some which she could not well describe to any, whose eyes had never been distempered, she answered me, that sometimes she thought she saw colours so new and glorious, that they were of a peculiar kind, and such as she could not describe by their likeness to any she had beheld either before or since; and that white objects did so much disorder her sight, that if, several days after her fall, she looked upon the inside of a book, she fancied she saw there colours like those of the rainbow: and even when she thought herself pretty well recovered, and made bold to leave her chamber, the coming into a place where the walls and ceiling were whited over, made those objects appear to her cloathed with such glorious and dazzling colours, as much offended her sight, and made her repent her venturousness; And she added, that this distemper of her eyes lasted not less than five or six weeks, though since that, she hath been able to read and write much without finding the least inconvenience in doing so. I would gladly have known, whether if she has shut the injured eye the phænomena would have been the same, when she employed only the other; but I heard not of this accident early enough to satisfy that inquiry.

9. WHEREFORE, I shall now add, that some years before, a person exceedingly eminent for his profound skill in almost all kinds of philological learning, coming to advise with me about a distemper in his eyes, told me, among other circumstances of it, that having upon a time looked too fixedly upon the sun, thorough a telescope, without any coloured glass, to take off from the dazzling splendor of the object, the excess of light did so strongly affect his eye, that ever since, when he turns it towards a window, or any white object, he fancies he seeth a globe of light, of about the bigness; the sun then appeared of to him, to pass before his eyes: and having inquired of him, how long he had been troubled with this indisposition, he replied, that it was already nine or ten years since the accident, that occasioned it, first befel him.

10. I COULD here subjoin, Pyrophilus, some memorable relations that I have met with in the account given us by the experienced Epiphanius Ferdinandus, of the symptoms he observed to be incident to those that are bitten with the Tarantula; by which (relations) I could probably shew, that without any change in the object, a change in the instruments of vision may for a great while make some colours appear charming, and make others provoking, and both to a high degree, though neither of them produced any such effect before. These things, I say, I could here subjoin in confirmation of what I have been saying, to shew that the disposition of the organ is of great importance in the dijudications we make of colours, were it not that these strange stories belonging more properly to another discourse, I had rather (contenting myself to have given you an intimation of them here) that you should meet with them fully delivered there.

1. BUT, Pyrophilus, I would not, by all that I have hitherto discoursed, be thought to have forgotten the distinction (of colour) that I mentioned to you about the beginning of the third session of the former chapter; and therefore, after all I have said of colour, as it is modified light, and immediately affects the sensory, I shall now remind you, that I did not deny, but that colour might, in some sense be considered as a quality residing in the body that is said to be coloured; and indeed the greatest part of the following experiments refer to colour principally under that notion, for there is in the bodies we call coloured, and chiefly in their superficial parts, a certain disposition, whereby they do so trouble the light that comes from them to our eye, as that it there makes that distinct impression, upon whose account we say, that the seen body is either white or black, or red or yellow, or of any one determinate colour. But because we shall (God permitting) by the experiments that are to follow some pages hence, more fully and particularly shew, that the changes, and consequently in divers places the production and the appearance of colours, depends upon the continuing or altered texture of the object we shall in this place intimate (and that too but as by the way) two or three things about this matter.

2. AND first, it is not without some reason, that I ascribe colour (in the sense formerly explained) chiefly to the superficial parts of bodies; for not to question how much opacous corpuscles may abound even in those bodies we call diaphanous, it seems plain that of opacous bodies we do indeed see little else than the superficies. For if we found the beams of light that rebound from the object to the eye, to pierce deep into the coloured body, we should not judge it opacous, but either translucid, or at least semi-diaphanous: and though the schools seem to teach us that colour is a penetrative quality, that reaches to the innermost parts of the object, as if a piece of sealing-wax be broken into never so many pieces, the internal fragments will be as red as the external surface did appear; yet that is but a particular example, that will not overthrow the reason lately offered, especially since I can allege other examples of a contrary import and two or three negative instances are sufficient to overthrow the generality of a positive rule, especially if that be built but upon one or a few examples. Not (then) to mention cherries, plums, and I know not how many other bodies, wherein the skin is of one colour, and what it hides of another, I shall name a couple of instances drawn from the colours of durable bodies that are thought far more homogeneous, and have not parts that are either organical, or of a nature approaching thereunto.

3. To give you the first instance, I shall need but to remind you of what I told you a little after the beginning of this essay, touching the blue and red and yellow, that may be produced upon a piece of tempered steel; for these colours, though they be very vivid, yet if you break the steel they adorn, they will appear to be but superficial; not only the innermost parts of the metal, but those that are within a hair's breadth of the superficies, having not any of these colours, but retaining that of the steel itself. Besides that, we may as well confirm this observation, as some other particulars we elsewhere deliver concerning colours, by the following experiment which we purposely made.

4. WE took a good quantity of clean lead, and melted it with a strong fire, and then immediately pouring it out into a clean vessel of a convenient shape and matter (we used one of iron, that the great and sudden heat might not injure it) and then carefully and nimbly taking off the scum that floated on the top, we perceived, as we expected, the smooth and glossy surface of the melted matter to be adorned with a very glorious colour, which being as transitory as delightful, did almost immediately give place to another vivid colour, and that was as quickly succeeded by a third, and this as it were chased away by a fourth; and so these wonderfully vivid colours successively appeared and vanished (yet the same now and then appearing the second time) till the metal ceasing to be hot enough to afford any longer this pleasing spectacle, the colours that chanced to adorn the surface, when the lead thus began to cool, remained upon it; but were so superficial, that how little soever we scraped off the surface I the lead, we did in such places scrape off all the colour, and discover only that which is natural to the metal itself; which receiving its adventitious colours, only when the heat was very intense, and in that part which was exposed to the comparatively very cold air (which by other experiments seems to abound with subtile saline parts, perhaps not uncapable of working upon lead so disposed:) these things, I say, together with my observing that whatever parts of the so strongly melted lead were exposed a while to the air, turned into a kind of scum or lithargre, how bright and clean soever they appeared before, suggested to me some thoughts or ravings, which I have not now time to acquaint you with. One that did not know me, Pyrophilus, would perchance think I endeavoured to impose upon you by relating this experiment, which I have several times tried; but the reason why the phænomena mentioned have not been taken notice of, may be, that unless lead be brought to a much higher degree of fusion or fluidity than is usual, or than is indeed requisite to make it melt, the phænomena I mentioned will scarce at all disclose themselves; and we have also observed, that this successive appearing and vanishing of vivid colours was wont to be impaired or determined whilst the metal exposed to the air remained yet hotter than one would readily suspect. And one thing I must further note, of which I leave you to search after the reason, namely, that the same colours did not always and regularly succeed one another, as is usual in steel, but in the diversified order mentioned in this following note, which I was scarce able to write down, the succession of the colours was so very quick: whether that proceeded from the differing degrees of heat in the lead exposed to the cool air, or from some other reason, I leave you to examine.

5. THE Atomists of old, and some learned men of late, have attempted to explicate the variety of colours in opacous bodies from the various figures of their superficial parts; the attempt is ingenious, and the doctrine seems partly true: but I confess I think there are divers other things that must be taken in as concurrent to produce those differing forms of asperity, whereon the colours of opacous bodies seem to depend. To declare this a little, we must assume, that the surfaces of all such bodies, how smooth or polite soever they may appear to our dull sight and touch, are exactly smooth only in a popular, or at most in a physical sense, but not in a strict and rigid sense.

6. THIS excellent microscopes shew us in many bodies, that seem smooth to our naked eyes; and this not only as to the little hillocks or protuberances that swell above that which may be conceived to be the plane or level of the considered surface; for it is obvious enough to those that are any thing conversant with such glasses: but as to numerous depressions beneath that level, of which sort of cavities, by the help of a microscope, which the greatest artificer that makes them, judges to be the greatest magnifying glass in Europe, except one that equals it, we have on the surface of a thin piece of cork that appeared smooth to the eye, observed about sixty in a row, within the length of less than a 31 and 32d part of an inch (for the glass takes in no longer a space at one view;) and these cavities (which made that little piece of cork almost like an empty honey-comb) were not only very distinct and figured like one another, but of a considerable bigness, and a scarce credible depth; insomuch that their distinct shadows as well as sides were plainly discerned and easy to be reckoned, and might have been well distinguished, though they had been ten times lesser than they were. Which I thought it not amiss to mention to you, Pyrophilus, upon the by, that you may thence make some estimate, what a strange inequality, and what a multitude of little shades there may really be, in a scarce sensible part of the physical superficies, though the naked eye sees no such matter. And as excellent microscopes shew us this ruggedness in many bodies that pass for smooth, so there are divers experiments, though we must not now stay to urge them, which seem to persuade us of the same thing, as to the rest of such bodies as we are now treating of; so that there is no sensible part of an opacous body, that may not be conceived to be made up of a multitude of singly insensible corpuscles. But in the giving these surfaces that disposition, which makes them alter the light that reflects thence to the eye after the manner requisite to make the object appear green, blue, &c the figures of these particles have a great, but not the only stroke. It is true indeed, that the protuberant particles may be of very great variety of figures, spherical, elliptical, polyedrical, and some very irregular; and that according to the nature of these, and the situation of the lucid body, the light must be variously affected, after one manner from surfaces (I now speak of physical surfaces) consisting of spherical, and in and other from those that are made up of conical or cylindrical corpuscles, some being fitted to reflect more of the incident beams of light, others less, and some towards one part, others towards another. But besides this difference of shape, there may be divers other things that may eminently concur to vary the forms of asperity that colours so much depend on. For, willingly allowing the figure of the particles in the first place, I confider secondly, that the superficial corpuscles, if I may so call them, may be bigger in one body, and less in another, and consequently fitted to allay the light falling on them with greater shades. Next, the protuberant particles may be set more or less close together, that is, there may be a greater or a smaller number of them within the compass of one, than within the compass of another small part of the surface of the same extent; and how much these qualities may serve to produce colour, may be somewhat guessed at, by that which happens in the agitation of water: for if the bubbles that are thereby made be great, and but few, the water will scarce acquire a sensible colour; but if it be reduced to a froth, consisting of bubbles, which being very minute and contiguous to each other, are a multitude of them crowded into a narrow room, the water (turned to froth) does then exhibit a very manifest white colour, to which these last named conditions of the bubbles do, well as their convex figure, contribute; and that for reasons to be mentioned anon. See the Discourse of the nature of whiteness and blackness Besides, it is not necessary that the superficial particles that exhibit one colour should be all of them round, or all conical, or all of any one shape; but corpuscles of differing figures may be mingled on the surface of the opacous body, as when the corpuscles that make a blue colour, and those, that make a yellow, come to be accurately and skillfully mixed, they make up a green; which, though it seem one simple colour, yet, in this case, appears to be made by corpuscles of very differing kinds, duly commixed. Moreover, the figure and bigness of the little depressions, cavities, furrows, or pores intercepted betwixt these protuberant corpuscles, are as well to be considered as the sizes and shapes of the corpuscles themselves: for we may conceive the physical superficies of a body, where (as we said) its colour does, as it were, reside, to be cut transversely by a mathematical plane, which you know is conceived to be without any depth or thickness at all; and then, as some parts of the physical superficies will be protuberant, or swell above this last plane, so others may be depressed beneath it, as (to explain myself by a gross comparison) in divers places of the surface of the earth, there are not only neighboring hills, trees, &c. that are raised above the horizontal level of the valley, but rivers, wells, pits and other cavities that are depressed beneath it. And that such protuberant and concave parts of a surface may remit the light so differingly, as much to vary a colour, some examples, and other things that we shall hereafter have occasion to take notice of in this tract, will sufficiently declare; till when, it may suffice to put you in mind, that of two flat sides of the same piece of, for example, red marble, the one being diligently polished, and the other left to its former roughness, the differing degrees or sorts of asperity, for the side that is shiooth to the touch wants not its roughness, will so diversify the light reflected from the several planes to the eye, that a painter would employ two differing colours to represent them.

7. AND I hope, Pyrophilus, you will not think it strange or impertinent, that I employ, in divers passages of these papers, examples drawn from bodies and shadows far more gross than those minute protuberances and shady pores on which, in most cases, the colour of a body, as it is an inherent quality or disposition of its surface, seems to depend, For sometimes I employ such examples, rather to declare my meaning, than prove any conjecture; things, whom their smallness makes insensible, being better represented to the imagination by such familiar objects, as being like them enough in other respects, are of a visible bulk. And next, though the beams of light are such subtile bodies, that in respect of them, even surfaces that are sensibly smooth, are not exactly so, have their own degree of roughness, consisting of little protuberances and depressions; and though consequently such inequalities may suffice to give bodies differing colours, as we see in marble that appears white or black, or red or blue, even when the most carefully polished; yet it is plain, by the late instance of red marble, and many others, that even bigger protuberances and greater shades may likewise so diversify the roughness of a body's superficies, as manifestly to concur to the varying of its colour, whereby such examples appear to be proper enough to be employed in such a subject as we have now in hand. And having hinted thus much on this occasion, I now proceed.

8. THE situation also of the superficial particles is considerable, which I distinguish into the posture of the single corpuscles, in respect of the light, and of the eye, and the order of them in reference also to one another; for a body may otherwise reflect the light, when its superficial particles are more erected upon the plane, that may be conceived to pass, along their basis, and when the points or extremes of such articles are obverted to the eye, than when those particles are so inclined, that their sides are in great part discernible; as the colour of plush or velvet will appear varied to you, if you carefully stroke part of it one way, and part of it another; the posture of the particular thrids, in reference to the light, or the eye, becoming thereby different. And you may observe in a field of ripe corn blown upon by the wind, that there will appear as it were waves of a colour (at least gradually) differing from that of the rest of the field the wind, by depressing some of the ears, and not at the same time others, making the one reflect more from the lateral and strawy parts than do the rest. And so, when dogs are so angry as to erect the hairs upon their necks, and upon some other parts of their bodies, those parts seem to acquire a colour varied from that which the same hairs made, when in their usual posture they did far more stoop. And that the order wherein the superficial corpuscles are ranged, is not to be neglected, we may guess by turning of water into froth, the beating of glass, and the scraping, of horns, in which cases the corpuscles that were before so marshalled as to be perspicuous, do by the troubling of that order become disposed to terminate and reflect more light, and thereby to appear whitish. And there are other ways in which the order of the protuberant parts, in reference to the eye, may much contribute to the appearing of a particular colour , for I have often observed, that when peas are planted, or set in parallel lines, and are shot up about half a foot above the surface of the ground, by looking on the field or plot of ground from that part towards which the parallel lines tended, the greater part of the ground by far, would appear of its own dirty colour; but if I looked upon it transversely, the plot would appear very green, the upper parts of the peas hindering the intercepted parts of the ground, which, as I said, retained their wonted colour from being discovered by the eye. And I know not, Pyrophilus, whether I might not add, that even the motion of the small parts of a visible object may in some cases contribute, though it be not so easy to say how, to the producing, or the varying of a colour: for I have several times made a liquor which, when it has well settled in a close phial, is transparent and colourless; but as soon as the glass is unstopped, begins to fly away very plentifully in a white and opacous fume. And there are other bodies, whose fumes, when they fill a receiver, would make one suspect it contains milk; and yet when these fumes settle into a liquor, that liquor is not white, but transparent and such white fumes I have seen afforded by unstopping a liquor I know, which yet is itself diaphanous and red: nor are these the only instances of this kind, that our trials can supply us with. And if the superficial corpuscles be of the grosser sort, and be so framed, that their differing sides or faces may exhibit differing colours, then the motion or rest of those corpuscles may be considerable, as to the colour of the superficies they compose; upon this account, that sometimes more, sometimes fewer of the sides disposed to exhibit such a colour may by this means become or continue more obverted to the eye than the rest, and compose a physical surface, that will be more or less sensibly interrupted. As, to explain my meaning, by proposing a gross example, I remember, that in some sorts of leafy plants thick set by one another, the two sides of whose leaves were of somewhat differing colours, there would be a notable disparity as to colour, if you looked upon them both, when the leaves, being at rest, had their upper and commonly exposed sides obverted to the eye, and when a breath of wind passing thorough them, made great numbers of the usually hidden sides of the leaves become conspicuous. And though the little bodies we were lately speaking of, may singly and apart seem almost colourless; yet when many of them are placed other, so near that the eye does not easily discern an interruption, within a sensible space, they may exhibit a colour: as we see, that though the slenderest thrid of dyed silk does whilst looked on single, seem. almost quite devoid of redness (for instance) yet when numbers of these thrids are brought together into one skein, their colour becomes notorious.

9. BUT the same occasion that invited me to say what I have mentioned concerning the leaves of trees, invites me also to give you some account of what happens in changeable taffaties, where we see differing colours, as it were, emerge and vanish upon the ruffling of the same piece of silk; as I have divers times with pleasure observed, by the help of such a microscope, as though it do not very much magnify the object, has in recompence this great conveniency, that you may easily, as fast as you please, remove it from one part to another of a large object, of which the glass taking a great part at once, you. may thereby presently survey the whole. Now by the help of such a microscope I could easily (as I began to say) discern, that in a piece of changeable taffaty (that appeared, for instance, sometimes red, and sometimes green) the stuff was composed of red thrids and green, passing under and over each other, and crossing one another in almost innumerable points: and if I looked through the glass upon any considerable portion of the stuff that (for example sake) to the naked eye appeared to be red, I could plainly see, that in that position, the red thrids were conspicuous, and reflected a vivid light. And though I could also perceive, that there were green ones, yet by reason of their disadvantageous position in the physical surface of the taffaty, they were in part hid by the more protuberant thrids of the other colour: and for the same cause, the reflection from as much of the green as was discovered, was comparatively but dim and faint. And if, on the contrary, I looked through the microscope upon any part that appeared green, I could plainly see that the red thrids were left fully exposed to the eye, and obscured by the green ones, which therefore made up the predominant colour. And by observing the texture of the silken stuff, I could easily so expose the thrids either of the one colour or of the other, to my eye, as at pleasure to exhibit an apparition of red or green, or make those colours succeed one another: so that, when I observed their succession by the help of the glass, I could mark how the predominant colour did as it were start out, when the thrids that exhibited it came to be advantageously placed; and by making little folds in the stuff after a certain manner, the sides that met and terminated in those folds, would appear to the naked eye, one of them red, and the other green. When thrids of more than two differing colours chance to be interwoven, the resulting changeableness of the taffaty may be also somewhat different, but I chuse to give an instance in the stuff I have been speaking of, because the mixture being more simple, the way whereby the changeableness is produced, may be the more easily apprehended: and though reason alone might readily enough lead a considering man to guess at the explication, in case he knew how changeable taffaties are made; yet I thought it not impertinent to mention it, because both scholars and gentlemen are wont to look upon the inquiry into manufactures, as a mechanic employment, and consequently below them; and because also with such a microscope as have been mentioning, the discovery is as well pleasant as satisfactory, and may afford hints of the solution of other phænomena of colours. And it were not amiss that some diligent inquiry were made, whether the microscope would give us an account of the variableness of colour, that is so conspicuous and so delightful in mother of pearl, in opals, and some other resembling bodies. For though I remember I did formerly attempt something of that kind (fruitlessly enough) upon mother of pearl, yet not having then the advantage of my best microscope, nor some conveniencies that might have been wished, I leave it to you, who have better eyes, to try what you can do further; since it will be same discovery to find, that in this case the best eyes and microscopes themselves can make none.

10. I CONFESS, Pyrophilus, that a great part of what I have delivered (or proposed rather) concerning the differing forms of asperity in bodies, by which differences, the incident light either comes to be reflected with more or less of shade, and with that shade more or less interrupted, or else happens to be also otherwise modified or troubled, is but conjectural. But I am not sure, that if it were not for the dulness of our senses, either these or some other notions of kin to them, might be better countenanced; for I am apt to suspect, that if we were sharp-sighted enough, or had such perfect microscopes, as I fear are more to be wished than hoped for, our promoted sense might discern in the physical surfaces of bodies, both a great many latent ruggednesses, and the particular sizes, shapes, and situations of the extremely little bodies that cause them, and perhaps might perceive among other varieties that we now can but imagine, how those little protuberances and cavities do interrupt and dilate the light, by mingling with it a multitude of little and singly undiscernable shades, though some of them more, and some of them less minute, some less, and some more numerous, according to the nature and degree of the particular colour we attribute to the visible object. As we see, that in the moon we can with excellent telescopes discern many hills and valleys, and as it were pits and other parts, whereof some are more, and some less vividly illustrated, and others have a fainter, others a deeper shade, though the naked eye can discern no such matter in that planet. And with an excellent microscope, where the naked eye did see but a green powder, the affected eye, as we noted above, could discern particular granules, some of them of a blue, and some of them of a yellow colour, which corpuscles we had beforehand caused to be exquisitely mixed to compound the green.

11. AND Pyrophilus, that you may not think me altogether extravagant in what I have said of the possibility (for I speak of no more) of discerning the differing forms of asperity in the surfaces of bodies of several colours, I'll here set down a memorable particular that chanced to come to my knowledge, since I writ a good part of this essay; and it is this. Meeting casually the other day with the deservedly famous Dr. F. Finch, (Since for his excellent qualities and loyalty, graced by his Majesty with the honour of knighthood.) extraordinary anatomist to that great patron of the Virtuosi, the now Great Duke of Tuscany, and inquiring of this ingenious person, what might be the chief rarity he had seen in his late return out of Italy into England, he told me, it was a man at Maestricht in the Low-Countries, who at certain times can discern and distinguish colours by the touch with his fingers. You will easily conclude, that this is far more strange than what I proposed but as not impossible; since the sense of the retina seeming to be much more tender and quick than that of those grosser filaments, nerves or membranes of our fingers, wherewith we use to handle gross and hard bodies, it seems scarce credible, that any accustomance, or diet, or peculiarity of constitution, should enable a man to distinguish, with such gross and unsuitable organs, such nice and subtile differences as those of the forms of asperity, that belong to differing colours; to receive whose languid and delicate impressions by the intervention of light, nature seems to have appointed and contexed into the retina the tender and delicate pith of the optic nerve. Wherefore I confess, I proposed divers scruples, and particularly whether the doctor had taken care to bind a napkin or handkerchief over his eyes so carefully, as to be sure he could make no use of his sight, though he had but counterfeited the want of it; to which I added divers other questions, to satisfy myself, whether there were any likelihood of collusion or other tricks. But I found that the judicious doctor having gone far out of his way, purposely to satisfy himself and his learned prince about this wonder, had been very watchful and circumspect to keep himself from being imposed upon. And that he might not through any mistake in point of memory misinform me, he did me the favour, at my request, to look out the notes he had written for his own and his prince's information, the sum of which memorials, as far as we shall mention them here, was this, that the doctor having been informed at Utrecht, that there lived one at some miles distance from Maestricht, who could distinguish colours by the touch; when he came to the last named town, he sent a messenger for him, and having examined him, was told upon inquiry these particulars.

THAT the man's name was John Vermaasen, at that time about 33 years of age that when he was but two years old, he had the small-pox, which rendered him absolutely blind; that at this present he is an, organist, and serves that office in a public choir.

THAT the doctor discoursing with him over night, the blind man affirmed, that he could distinguish colours by the touch, but that he could not do it, unless he were fasting; any quantity of drink taking from him that exquisiteness of touch, which is requisite to so nice a sensation.

THAT hereupon the doctor provided against the next morning seven pieces of ribbon, of these seven colours, black, white, red, blue, green, yellow, and grey but as for mingled colours, this Verinaasen would not undertake to discern them, though if offered, he would tell that they were mixed.

THAT to discern the colour of the ribbon, he places it betwixt the thumb and the forefinger, but his most exquisite perception was in his thumb, and much better in the right thumb than in the left.

THAT after the blind man had four or five times told the doctor the several colours (though blinded with a napkin for fear he might have some sight) the doctor found he was twice mistaken, for he called the white black, and the red blue; but still, he, before his error, would lay them by in pairs, saving, that though he could easily distinguish them from all others, yet those two pairs were not easily distinguished amongst themselves. Whereupon the doctor desired to be told by him what kind of discrimination he had of colours by his touch, to which he gave a reply, for whose sake chiefly I insert all this narrative in this place I namely, that all the difference was more or less asperity, for says he (I give you the doctor's own words) black feels as if you were feeling needles points, or some harsh sand, and red feels very smooth.

THAT the doctor having desired him to tell in order the difference of colours to his touch, he did as follows.

BLACK and white are the most asperous or unequal of all colours, and so like, that it is very hard to distinguish them; but black is the most rough of the two; green is next in asperity, grey next to green in asperity, yellow is the fifth in degree of asperity: red and blue are so like, that they are as hard to distinguish as black and white; but red is somewhat more asperous than blue, so that red has the sixth place, and blue the seventh in asperity.

12. To these informations the obliging doctor was pleased to add the welcome present of three of those very pieces of ribbon, whose colours in his presence the blind man had distinguished, pronouncing the one grey, the other red, and the third green I which I keep by me as rarities, and the rather, because he feared the rest were miscarried.

13. BEFORE I saw the notes that afforded me the precedent narrative, I confess I suspected this man might have thus discriminated colours rather by the smell than by the touch; for some of the ingredients imployed by dyers to colour things, have scents, that are not so languid, nor so near of kin: but that I thought it not impossible that a very critical nose might distinguish them, and this I the rather suspected, because he required, that the ribbons, whose colours he was to name, should be offered him fasting in the morning; for I have observed in setting dogs, that the feeding of them (especially with some sorts of aliments) does very much impair the exquisite scent of their noses. And though some of the foregoing particulars would have prevented that conjecture, yet I confess to you (Pyrophilus) that I would gladly have had the opportunity of examining this man myself, and of questioning him about divers particulars which I do not find to have been yet thought upon. And though it be not incredible to me, that since the liquours that dyers employ to tinge, are qualified to do so by multitudes of little corpuscles of the pigment or dying stuff, which are dissolved and extracted by the liquor, and swim to and fro in it, those corpuscles of colour (as the Atomists call them) insinuating themselves into, and filling all the pores of the body to be dyed, may asperate its superficies more or less according to the bigness and texture of the corpuscles of the pigment; yet I can scarce believe, that our blind man could distinguish all the colours he did, meerly by the ribbons having more or less of asperity; so that I cannot but think, notwithstanding this history, that the blind man distinguished colours not only by the degrees of asperity in the bodies offered to him, but by forms of it, though this (latter) would perhaps have been very difficult for him to make an intelligible mention of, because those minute disparities having not been taken notice of by men for want of touch as exquisite as our blind man's, are thin as he could not have intelligibly expressed; which will easily seem probable, if you confider, that under the name of sharp, and sweet, and sour, there are abundance of, as it were, immediate peculiar relishes or tastes in differing sorts of wine, which, though critical and experienced palates can easily discern themselves, cannot make them be understood by others such minute differences not having hitherto any distinct names assigned them. And it seems that there was something in the forms of asperity that was requisite to the distinction of colours, besides the degree of it, since he found it so difficult to distinguish black and white from one another, though not from other colours. For I might urge, that he seems not consonant to himself about the red, which, as you have seen in one place, he represents as somewhat more asperous than the blue; and in another, very smooth but because he speaks of this smoothness in that place, where he mentions the roughness of black, we may favourably presume that he might mean but a comparative smoothness; and therefore I shall not insist on this, but rather countenance my conjecture by this, that he found it so difficult, not only to discriminate red and blue (though the first of our promiscuous experiments will inform you, that the red reflects by great odds more light than the other) but also to distinguish black and white from one another, though not from other colours. And indeed, though in the ribbons that were offered him, they might be almost equally rough, yet in such slender corpuscles, as those of colour, there may easily enough be conceived, not only a greater closeness of parts, or else paucity of protuberant corpuscles, and the little extant particles may be otherwise figured, and ranged in the white than in the black, but the cavities may be much deeper in the one than the other.

14. AND perhaps (Pyrophilus) it may prove some illustration of what I mean, and help you to conceive how this may be, if I represent, that where the particles are so exceeding slender, we may allow the parts exposed to the sight and touch to be a little convex in comparison of the erected particles of black bodies, as if there were wires I know not how many times slenderer than a hair: whether you suppose them to be figured like needles, or cylindrically, like the hairs of a brush, with hemispherical (or at least convex) tops, they will be so very slender, and consequently the points both of the one sort and the other so very sharp, that even an exquisite touch will be able to distinguish no greater difference between them, than that which our blind man allowed, when comparing black and white bodies, he said, that the latter was the less rough of the two. Nor is every kind of roughness, though sensible enough, inconsistent with whiteness, there being cases, wherein the physical superficies of a body is made by the same operation both rough and white; as when the level surface of clear water being by agitation asperated with a multitude of unequal bubbles, does thereby acquire a whiteness; and as a smooth piece of glass, by being scratched with a diamond, does in the asperated part of its face disclose the same colour. But more (perchance) of this elsewhere.

15. AND therefore, we shall here pass by the question, whether any thing might be considered about the opacity of the corpuscles of black pigments, and the comparative diaphaneity of the of many white bodies, applied to our present case; and proceed to represent, that the newly mentioned exiguity and shape of the extant particles being supposed, it will then be considerable what we lately but hinted (and therefore must now somewhat explain) that the depth of the little cavities, intercepted between the extant particles, without being so much greater in black bodies than in white ones, as to be perceptibly so to the gross organs of touch, may be very much greater in reference to their disposition of reflecting the imaginary subtile beams of light. For in black bodies, those little intercepted cavities, and other depressions, may be so figured, so narrow and so deep, that the incident beams of light, which the more extant parts of the physical superficies are disposed to reflect inwards, may be detained there, and prove unable to emerge; whilst, in a white body, the slender particles may not only by their figure be fitted to reflect the light copiously outwards, but the intercepted cavities being not deep, nor perhaps very narrow, the bottoms of them may be so constituted, as to be fit to reflect outwards much of the light that falls even upon them; as you may possibly better apprehend, when we shall come to treat of whiteness and blackness. In the mean time, it may suffice, that you take notice with me, that the blind man's relations import no necessity of concluding, that though, because, according to the judgment of his touch, black was the roughest, as it is the darkest of colours, therefore white, which (according to us) is the lightest, should be also the smoothest: since I observe, that he makes yellow to be two degrees more asperous than blue, and as much less asperous than green; whereas, indeed, yellow does not only appear to the eye a lighter colour than blue, but (by our first experiment hereafter to be mentioned) it will appear, that yellow reflected much more light than blue, and manifestly more than green; which we need not much wonder at, since in this colour, and the two others (blue and yellow) it is not only the reflected light that is to be considered, since to produce both these, refraction seems to intervene, which by its varieties may much alter the case: which both seems to strengthen the conjecture I was formerly proposing, that there was something else in the kinds of asperity, as well as in the degrees of it, which enabled our blind man to discriminate colours, and does at least show, that we cannot, in all cases, from the bare difference in the degrees of asperity betwixt colours, safely conclude, that the rougher of any two always reflects the least light.

16. BUT this notwithstanding (Pyrophilus) and whatever curiosity I may have had to move some questions to our sagacious blind man; yet thus much I think you will admit us to have gained by his testimony, that since many colours may be felt with the circumstances above related, the surfaces of such coloured bodies must certainly have differing degrees, and in all probability have differing forms or kinds of asperity belonging to them, which is all the use that my present attempt obliges me to make of the history above delivered ; that being sufficient to prove, that colour does much depend upon the disposition of the superficial parts of bodies, and to shew in general, wherein it is probable that such a disposition does (principally at least) consist.

17. BUT to return to what I was saying, before I began to make mention of our blind organist; what we have delivered touching the causes of the several forms of asperity that may diversify the surfaces of coloured bodies, may perchance somewhat assist us to make some conjectures in the general, at several of the ways whereby it is possible for the experiments, hereafter to be mentioned, to produce the sudden changes of colours; that are wont to be consequent upon them: for most of these phænomena being produced by the intervention of liquors, and these for the most part abounding with very minute, active, and variously figured saline corpuscles, liquors so qualified may well enough very nimbly alter the texture of the body they are employed to work upon, and so may change the form of asperity, and thereby make them remit to the eye the light that falls on them after another manner than they did before, and by that means vary the colour, so far forth as it depends upon the texture or disposition of the seen parts of the object; which I say, Pyrophilus, that you may not think I would absolutely exclude all other ways of modifying the beams of light between their parting from the lucid body, and their reception into the common sensory.

18. NOW there seem to me divers ways, by which we may conceive that liquors may nimbly alter the colour of one another, and of other bodies, upon which they act; but my present haste will allow me to mention but some of them, without insisting so much as upon those I shall name.

19. AND first, the minute corpuscles that compose a liquor may easily insinuate themselves, into those pores of bodies, whereto their size and figure makes them congruous; and these pores they may either exactly fill, or but inadequately: and in this latter case they will for the most part alter the number and figure, and always the bigness of the former pores. And in what capacity soever these corpuscles of a liquor come to be lodged or harboured in the pores that admit them, surface of the body will for the most part have its asperity altered, and the incident light that meets with a grosser liquor in the little cavities that before contained nothing but air, or some yet subtiler fluid, will have its beams either refracted, or imbibed, or else reflected more or less interruptedly than they would be, if the body had been unmoistened: as we see, that even fair water falling on white paper, or linen, and divers other bodies apt to soak it in, will for some such reasons as those newly mentioned, immediately alter the colour of them, and for the most part make it sadder than that of the unwetted parts of the same bodies. And so you may see, that when in the summer the highways are dry and dusty, if there falls store of rain, they will quickly appear of a much darker colour than they did before; and if a drop of oil be let fall upon a sheet of white paper, that part of it, which by the imbibition of the liquor, acquires a greater continuity, and some transparency, will appear much darker than the rest, many of the incident beams of light being now transmitted, that otherwise would be reflected towards the beholder's eyes.

20. SECONDLY, A liquor may alter the colour of a body, by freeing it from those things that hindered it from appearing in its genuine colour; and though, this may be said to be rather a restoration of a body to its own colour, or a retection of its native colour, than a change, yet still there intervenes in it a change of the colour which the body appeared to be of before this operation. And such a change a liquor may work, either by dissolving, or corroding, or by some such way of carrying off that matter, which either veiled or disguised the colour that afterwards appears, Thus we restore old pieces of dirty gold to a clean and nitid yellow, by putting them into the fire, and into aqua-fortis, which take off the adventitious filth that made that pure metal look of a dirty colour: and there is also an easy way to restore silver coins to their due lustre, by fetching off that which discoloured them. And I know a chymical liquor, which I employed to restore pieces of cloth spotted with grease to their proper colour, by imbibing the spotted part with this liquor, which incorporating with the grease, and yet being of a very volatile nature, does easily carry it away with itself. And I have sometimes tried, that by rubbing upon a good touch-stone a certain metalline mixture so compounded, that the impression it left upon the stone appeared of a very differing colour from that of gold, yet a little of aqua-fortis would in a trice make the golden colour disclose itself, by dissolving the other metalline corpuscles that concealed those of the gold, which you know that menstruum will leave untouched.

21. THIRDLY, A liquor may alter the colour of a body by making a comminution of its parts, and that principally two ways; the first by disjoining and dissipating those clusters of particles, if I may so call them, which stuck more loosely together, being fastened only by some more easily dissoluble cement, which seems to be the case of some of the following experiments, where you will find the colour of many corpuscles brought to cohere by having been precipitated together, destroyed by the affusion of very piercing and incisive liquors. The other of the two ways I was speaking of, is, by dividing the grosser and more solid particles into minute ones, which will be always lesser, and for the most part otherwise shaped than the entire corpuscle so divided, as it will happen in a piece of wood reduced into splinters or chips, or as when a piece of crystal heated red-hot and quenched in cold water is cracked into a multitude of little fragments, which, though they fall not asunder, alter the disposition of a body of the crystal, as to its manner of reflecting the light, as we shall have occasion to shew hereafter.

22. THERE is a fourth way contrary to the third, whereby a liquor may change the colour of another body, especially of another fluid; and that is, by procuring the coalition of several particles that before lay too scattered and dispersed to exhibit the colour that afterwards appears. Thus sometimes when I have had the solution of gold so dilated, that I doubted whether the liquor had really imbibed any true gold or no, by pouring in a little mercury, I have been quickly able to satisfy myself, that the liquor contained gold; that metal after a little while cloathing the surface of the quicksilver with a thin film of its own livery. And chiefly, though not only by this way of bringing the minute parts of bodies together in such numbers, as to make them become notorious, to the eye, many of these colours seem to be generated which are produced by precipitations, especially by such as are wont to be made with fair water; as when resinous gums dissolved in spirit of wine, are let fall again, if the spirit be copiously diluted with that weakening liquor. And so out of the rectified and transparent butter of antimony, by the bare mixture of fair water, there will be plentifully precipitated that milk-white substance, which by having its looser salts well washed off, is turned into that medicine, which vulgar chymists are pleased to call Mercurius Vitæ.

23. A FIFTH way, by which a liquor may change the colour of a body, is, by dislocating the parts, and putting them out of their former order into another, and perhaps also altering the posture of the single corpuscles as well as their order or situation in respect of one another. What certain kinds of commotion or dislocation of the parts of a body may do towards the changing its colour, is not only evident in the mutations of colour observable in quicksilver, and some other concretes long kept by chymists in a convenient heat, though in close vessels, but in the obvious degenerations of colour, which every body may take notice of in bruised cherries, and other fruit, by comparing after a while the colour of the injured with that of the sound part of the same fruit. And that also such liquors, as we have been speaking of, may greatly discompose the textures of many bodies, and thereby alter the disposition of their superficial parts, the great commotion made in metals, and several other bodies by aqua-fortis, oil of vitriol, and other saline menstruums, may easily persuade us; and what such varied situations of parts may do towards the diversifying of the manner of their reflecting the light, may be guessed in some measure by the beating of transparent glass into a white powder, but far better by the experiments lately pointed at, and hereafter delivered, as the producing and destroying colours by the means of subtile saline liquors, by whose affusion the parts of other liquors are manifestly both agitated, and likewise disposed after another manner than they were before such affusion. And in some chymical oils, as particularly that of lemon peels, by barely shaking the glass that holds it into bubbles, that transposition of the parts which is consequent to the shaking, will shew you on the surfaces of the bubbles exceeding orient and lively colours, which, when the bubbles relapse into the rest of the oil, do immediately vanish.

24. I KNOW not, Pyrophilus, whether I should mention as a distinct way, because it is of a somewhat more general nature, that power whereby a liquor may alter the colour of another body, by putting the parts of it into motion; for though possibly the motion so produced does, as such, seldom suddenly change the colour of the body whose parts are agitated, yet this seems to be one of the most general, however not immediate causes of the quick change of colours in bodies. For the parts being put into motion by the adventitious liquor, divers of them that were before united, may become thereby disjoined, and when that motion ceases or decays, others of them may stick together, and that in a new order, by which means the motion may sometimes produce permanent changes of colours, as in the experiment you will meet with hereafter, of presently turning a snowy white body into a yellow, by the bare affusion of fair water, which probably so dissolves the saline corpuscles that remained in the calx, and sets them at liberty to act upon one another, and the metal, far more powerfully than the water without the assistance of such saline corpuscles could do. And though you rub blue vitriol, how venereal and unsophisticated soever it be, upon the whetted blade of a knife, it will not impart to the iron its latent colour; but if you moisten the vitriol with your spittle, or common water, the particles of the liquor disjoining those of the vitriol, and thereby giving them the various agitation requisite to fluid bodies, the metalline corpuscles of the thus dissolved vitriol will lodge themselves in throngs in the small and congruous pores of the iron they are rubbed on, and so give the surface of it the genuine colour of the copper.

25. THERE remains yet a way, Pyrophilus, to be mentioned, by which a liquor may alter the colour of another body, and this seems the most important of all, because though it be named but as one, yet it may indeed comprehend many; and that is, by associating the saline corpuscles, or any other sort of the more rigid ones of the liquor, with the particles of the body that it is employed to work upon. For these adventitious corpuscles associating themselves with the protuberant particles of the surface of a coloured body, must necessarily alter their bigness, and will most commonly alter their shape. And how much the colours of bodies depend upon the bulk and figure of their superficial particles, you may guess by this, that eminent antient philosophers, and divers moderns, have thought that all colours might, in a general way, be made out by these two; whose being diversified will, in our case, be attended with these two circumstances; the one, that the protuberant particles being increased in bulk, they will oftentimes be varied as to the closeness or laxity of their order, fewer of them being contained within the same sensible (though minute) space than before; or else by approaching to one another, they must straiten the pores, and it may be too they will, by their manner of associating themselves with the protuberant particles, intercept new pores. And this invites me to confider farther, that the adventitious corpuscles I have been speaking of, may likewise produce a great change, as well in the little cavities or pores, as in the protuberances of a coloured body; for, besides what we have just now taken notice of, they may, by lodging themselves in those little cavities, fill them up, and it may well happen, that they may not only fill the pores they insinuate themselves into, but likewise have their upper parts extant above them; and partly by these new protuberances, partly by increasing the bulk of the former, these extraneous corpuscles may much alter the number and bigness of the surface's pores, changing the old and intercepting new ones. And then it is odds, but the order of the little extancies, and consequently that of the little depressions in point of situation will be altered likewise: as if you dissolve quicksilver in some kind of aqua-fortis, the saline particles of the menstruum, associating themselves with the mercurial corpuscles, will make a green solution, which afterwards easily enough degenerates. And red lead, or minium, being dissolved in spirit of vinegar, yields not a red, but a clear solution, the redness of the lead being by the liquor destroyed. But a better instance may be taken from copper; for I have tried, that if upon a copper-plate, you let some drops of weak aqua-fortis rest for a while, the corpuscles of the menstruum joining with those of the metal, will produce a very sensible asperity upon the surface of the plate, and will coagulate that way into very minute grains of a pale blue vitriol whereas, if upon another of it of the same plate you suffer a little strong spirit of urine to rest a competent time, you shall find the asperated surface adorned with a deeper and richer blue. And the same aqua sortis, that will quickly change the redness of red lead into a darker colour, will, being put upon crude lead, produce a whitish substance, as with copper it did a blueish. And as with iron it will produce a reddish, and on white quills a yellowish, so, much may the coalition of the parts of the same liquor, with the differingly figured particles of stable bodies, divers ways asperate the differingly disposed surfaces, and so diversify the colour of those bodies. And you will easily believe, that in many changes of colour, that happen upon the dissolutions of metals, and precipitations made with oil of tartar, and the like fixed salts, there may intervene a coalition of saline corpuscles with the particles of the body dissolved or precipitated, if you examine how much the vitriol of a metal may be heavier than the metalline part of it alone, upon the score of the saline parts concoagulated therewith; and, that in several precipitations the weight of the calx does for the same reason much exceed that of the metal, when it was first put in to be dissolved.

26. BUT, Pyrophilus, to consider these matters more particularly would be to forget that I declared against adventuring, at least for this time, at particular theories of colours, and that accordingly you may justly expect from me rather experiments than speculations: and therefore I shall dismiss this subject of the forms of superficial asperity in coloured bodies, as soon as I shall but have named to you, by way of supplement to what we have hitherto discoursed in this short section, a couple of particulars (which you will easily grant me); the one, that there are divers other ways for the speedy production even of true and permanent colours in bodies, besides, those practicable by the help of liquors: for proof of which advertisement, though several examples might be alledged, yet I shall need but remind you of what I mentioned to you above, touching the change of colours suddenly made on tempered steel, and on lead, by the operation of heat, without the intervention of a liquor. But the other particular I am to observe to you, is of more importance to our present subject; and it is, that though nature and art may in some cases so, change the asperity of the superficial parts of a body, as to change its colour by either of the ways I have proposed, single or unassisted; yet for the most part it is by two or three, or perhaps by more of the forementioned ways associated together, that the effect is produced. And if you confider how variously these several ways and some others allied unto them, which I have left unmentioned, may be compounded and applied, you will not much wonder that such fruitful, whether principles (or manners of diversification) should be fitted to change or generate no small store of differing colours.

27. HITHERTO, Pyrophilus, we have in discoursing of the asperity of bodies considered the little protuberances of other superficial particles which make up that toughness, as if we took it for granted, that they must be perfectly opacous and impenetrable by the beams of light, and so, must contribute to the variety of colours, as they terminate more or less light, and reflect it to the eye mixed with more or less of thus or thus mingled shades. But to deal ingenuously with you, Pyrophilus, before I proceed any further, I must not conceal from you, that I have often thought it worth a serious inquiry, whether or no particles of matter, each of them singly insensible, and therefore small enough to be capable of being such minute particles, as the Atomists both of old and of late have (not absurdly) called Corpuscula Coloris, may not yet consist each of them of divers yet minuter particles, betwixt which we may conceive little commissures where they adhere to one another, and, however, may not be porous enough to be, at least in some degree, pervious to the unimaginably subtile corpuscles that make up the beams of light, and consequently to be in such a degree diaphanous. For, Pyrophilus, that the proposed inquiry may be of moment to him that searches after the nature of colour, you will easily grant, if you consider, that whereas perfectly opacous bodies can but reflect the incident beams of light, those that are diaphanous are qualified to refract them too; and that refraction has such a stroke in the production of colours, as you cannot but have taken notice of, and perhaps admired in the colours generated by the trajection of light through drops of water that exhibit a rainbow, through prismatical glasses, and through divers other transparent bodies. But 'tis like, Pyrophilus, you will more easily allow that about this matter it is rather important to have a certainty, than that it is rational to entertain a doubt; wherefore I must mention to you some of the reasons that make me think it may need a further inquiry: for I find that in a darkened room, where the light is permitted to enter but at one hole, the little wandering particles of dust, that are commonly called motes, and, unless in the sun-beams, are not taken notice of by the unassisted sight; I have, I say, often observed that these roving corpuscles being looked on by an eye placed on the one side of the beams that entered the little hole, and by the darkness having its pupil much enlarged, I could discern that these motes as soon as they came within the compass of the luminous, whether cylinder or inverted cone, if I may so call it, that was made up by the unclouded beams of the sun, did in certain positions appear adorned with very vivid colours, like those of the rainbow, or rather like those of very minute, but sparkling fragments of diamonds: and as soon as the continuance of their motion had brought them to an inconvenient position in reference to the light and the eye, they were only visible without darting any lively colours as before. Which seems to argue, that these little motes, or minute fragments of several sorts of bodies reputed opacous, and only crumbled as to their exterior and looser parts into dust, did not barely reflect the beams that fell upon them, but remit them to the eye refracted too. We may also observe, that several bodies (as well some of a vegetable, as others of an animal nature) which are wont to pass for opacous, appear in great part transparent, when they are reduced into thin parts, and held against a powerful light. This I have not only taken notice of in pieces of ivory reduced into thick leaves, as also in divers considerable thick shells of fishes and in shaving of wood; but I have also sound that a piece of deal, far thicker than one would easily imagine, being purposely interposed betwixt my eye placed in a room, and the clear day-light, was not only somewhat transparent, but (perhaps by reason of its gummous nature) appeared quite through of a lovely red. And in the darkened room above mentioned, bodies held against the hole at which the light entered, appeared far less opacous than they would elsewhere have done insomuch that I could easily and plainly see, through the whole thickness of my hand, the motions of a body placed (at a very near distance indeed, but yet) beyond it. And even in minerals, the opacity is not always so great as many think, if the body be made thin: for white marble, though of a pretty thickness, being within a due distance placed betwixt the eye and a convenient light, will suffer the motions of one's finger to be well discerned through it, and so will pieces, thick enough, of many common flints. But above all, that instance is remarkable, that is afforded us by Muscovy glass (which some call Selenites, others Lapis Specularis;) for though plates of this mineral, though but of a moderate thickness, do often appear opacous, yet if one of these be dexterously split into the thinnest leaves it is made up of, it will yield such a number of them, as scarce any thing but experience could have persuaded me; and these leaves will afford the most transparent sort of consistent bodies, that, for aught I have observed, are yet unknown; and a single leaf or plate will be so far from being opacous, that it will scarce be so much as visible. And multitudes of bodies there are, whose fragments seem opacous to the naked eye, which yet, when I have included them in good microscopes, appeared transparent; but, Pyrophilus, on the other side I am not yet sure that there are no bodies, whose minute particles even in such a microscope as that of mine, which I was lately mentioning, will not appear diaphanous. For having considered mercury precipitated per se, the little granules that made up the powder, looked like little fragments of coral beheld by the naked eye at a distance (for very near at hand coral will sometimes, especially if it be good, shew some transparency). Filings likewise of steel and copper, though in an excellent microscope, and a fair day, they showed like pretty big fragments of those metals, and had considerable brightness on some of their surfaces, yet I was not satisfied, that I perceived any reflection from the inner parts of any of the filings. Nay, having looked in my best microscope upon the red calx of lead (commonly called Minium) neither I, nor any I shewed it to, could discern it to be other than opacous, though the day were clear, and the object strongly enlightened. And the deeply red colour of vitriol appeared in the same microscope (notwithstanding the great comminution effected by the fire) but like grossy beaten brick. so that, Pyrophilus, I shall willingly resign you the care of making same further inquiries into the subject we have now been consider; for I confess, as I told you before, that I think that the matter may need a further scrutiny, nor would I be forward to determine how far or in what cases the transparency or semi-diaphaneity of the superficial corpuscles of bigger bodies may have an interest in the production of their colours; especially because that even in divers white bodies, as beaten glass, snow and froth, where it seems manifest that the superficial parts are singly diaphanous (being either water, or air, or glass) we see not that such variety of colours are produced as usually are by the refraction of light even in those bodies, when by their bigness, shape, &c. they are conveniently qualified to exhibit such various and lively colours as those of the rainbow, and of prismatical glasses.

28. By what has been hitherto discoursed, Pyrophilus, we may be assisted to judge of that famous controversy which was of old disputed betwixt the Epicureans and other Atomists on one side, and most other philosophers on the other side; the former denying bodies to be coloured in the dark, and the latter making colour to be an inherent quality, as well as figure, hardness, weight, or the like. For though this controversy be revived, and hotly agitated among the moderns, yet I doubt whether it be not in great part a nominal dispute; and therefore let us, according to the doctrine formerly delivered, distinguish the acceptations of the word colour, and say, that if it be taken in the stricter sense, the Epicureans seem to be in the right; for if colour be indeed, though not according to, them, but light modified, how can we conceive that it can subsist in the dark, that is, where it must be supposed there is no light: but, on the other side, if colour be considered as a certain constant disposition of the superficial parts of the object to trouble the light they reflect after such and such a determinate manner, this constant, and if I may so speak, modifying disposition persevering in the object, whether it be shined upon or no, there seems no just reason to deny, but that in this sense, bodies retain their colour as well, in the night as day; or, to speak a little otherwise, it may be said, that bodies are potentially coloured in the dark, and actually in the light. But of this matter discoursing more fully elsewhere, as it is a difficulty that concerns qualities in general, I shall forbear to insist on it here.

1. OF greater moment in the investigation of the nature of colours is the controversy, whether those of the rainbow, and those that are often seen in clouds, before the rising, or after the setting of the sun; and in a word, whether those other colours, that are wont to be called emphatical, ought or ought not to be accounted true colours. I need not tell you that the negative is the common opinion, especially in the schools, as may appear by that vulgar distinction of colours, whereby these under consideration are termed apparent, by way of opposition to those that in the other member of the distinction are called true or genuine. This question I say seems to me of importance, upon this account, that it being commonly granted (or however, easy enough to be proved) that emphatical colours are light itself modified by refractions chiefly, with a concurrence sometimes of reflections, and perhaps some other accidents depending on these two; if these emphatical colours be resolved to be genuine, it will seem consequent, that colours, or at least divers of them, are but diversified light, and not such real and inherent qualities as they are commonly thought to be.

2. NOW since we are wont to esteem the echoes and other sounds of bodies, to be true sounds, all their odours to be true odours, and (to be short) since we judge other sensible qualities to be true ones, because they are the proper objects of some or other of our senses; I see not why emphatical colours, being the proper and peculiar objects of the organ of sight, and capable to affect it as truly and as powerfully as other colours, should be reputed but imaginary ones.

AND if we have (which perchance you will allow) formerly evinced colour (when the word is taken in its more proper sense) to be but modified light, there will be small reason to deny these to be true colours, which more manifestly than others disclose themselves to be produced by diversifications of the light.

3. THERE is indeed taken notice of, a difference betwixt these apparent colours, and those that are wont to be esteemed genuine, as to the duration, which has induced some learned men to call the former rather evanid than fantastical. But as the ingenious Gassendus does somewhere judiciously observe, is this way of arguing were good, the greenness of a leaf ought to pass for apparent, because, soon fading into a yellow, it scarce lasts at all, in comparison of the greenness of an emerald. I shall add, that if the sun-beams be in a convenient manner trajected through a glass prism, and thrown upon some well shaded object within a room, the rainbow thereby painted on the surface of the body that terminates the beams, may oftentimes last longer than some colours I have produced in certain bodies, which would justly, and without scruple be accounted genuine colours, and yet suddenly degenerate, and lose their nature.

4. A GREATER disparity betwixt emphatical colours, and others, may perhaps be taken from this, that genuine colours seem to be produced in opacous bodies by reflection, but apparent ones in diaphanous bodies, and principally by refraction; I say principally, rather than solely, because in some cases reflection also may concur: but still this seems not to conclude these latter colours not to be true ones. Nor must what has been newly said of the differences of true and apparent colours, be interpreted in too unlimited a sense, and therefore it may perhaps somewhat assist you, both to repect upon the two foregoing objections, and to judge of some other passages which you will meet with in this tract, if I take this occasion to observe to you, that if water be agitated into froth, it exhibits, you know, a white colour, which soon after it loses upon the resolution of the bubbles into air and water. Now in this case either the whiteness of the froth is a true colour, or not; if it be, then true colours, supposing the water pure and free from mixtures of any thing tenacious, may be as short-lived as those of the rainbow; also the matter, wherein the whiteness did reside, may in a few moments perfectly lose all footsteps or remains of it. And besides, even diaphanous bodies may be capable of exhibiting true colours by reflection; for that whiteness is so produced, we shall anon make it probable. But if on the other side it be said, that the whiteness of froth is an emphatical colour, then it must no longer be said, that fantastical colours require a certain position of the luminary and the eye, and must be varied or destroyed by the change thereof, since froth appears white, whether the sun be rising or setting, or in the meridian, or any where between it and the horizon, and from what (neighbouring) place soever the beholder's eye looks upon it. And since by making a liquor tenacious enough, yet without destroying its transparency, or staining it with any colour, you may give the little films, whereof the bubbles consist, such a texture as may make the froth last very many hours, if not some days, or even weeks, it will render it somewhat improper to assign duration for the distinguishing character to discriminate genuine from fantastical colours. For such froth may much outlast the undoubtedly true colours of some of nature's productions, as in that gaudy plant, not undeservedly called the Marvel of Peru, the flowers do often fade the same day they are blown; and I have often seen, a Virginian flower, which usually withers within the compass of a day; and I am credibly informed, that not far from hence, a curious herborist has a plant, whose flowers perish in about an hour. But, if the whiteness of water turned into froth must therefore be reputed emphatical, because it appears not that the nature of the body is altered, but only that the disposition of its parts, in reference to the incident light, is changed, why may not the whiteness be accounted emphatical too; which I shall shew anon to be producible, barely by such another change in black horn: and yet this so easily acquired whiteness seems to be as truly its colour as the blackness was before, and at least is more permanent than the greenness of leaves, the redness of roses, and in short, than the genuine colours of the most part of nature's productions. It may indeed be further objected, that according as the sun or other luminous body changes place, these emphatical colours alter or vanish. But not to repeat what I have just now said, I shall add, that if a piece of cloth in a draper's shop (in such the light being seldom primary) be variously folded, it will appear of differing colours, as the parts happen to be more illuminated, or more shaded; and if you stretch it flat, it will commonly exhibit some one uniform colour: and yet these are not wont to be reputed emphatical, so that the difference seems to be chiefly this, that in the case of the rainbow, and the like, the position of the luminary varies the colour, and in the cloth I have been mentioning, the position of the object does it. Nor am I forward to allow, that in all cases, the apparition of emphatical colours requires a determinate position of the eye; for if men will have the whiteness of froth emphatical, you know what we have already inferred from thence. Besides, the sunbeams trajected through a triangular glass, after the manner lately mentioned, will, upon the body that terminates them, paint a rainbow, that may be seen, whether the eye be placed on the right hand of it, or the left, or above, or beneath it, or before or behind it: and though there may appear some little variation in the colours of the rainbow beheld from differing parts of the room, yet such a diversity may be also observed by an attentive eye in real colours, looked upon under the like circumstances. Nor will it follow, that because there remain no footsteps of the colour upon the object, when the prism is removed, that therefore the colour was not real, since the light was truly modified by the refraction and reflection it suffered in its trajection through the prism; and the object in our case served for a specular body, to reflect that colour to the eye. And that you may not be startled, Pyrophilus, that I should venture to say, that a rough and coloured object may serve for a speculum to reflect the artificial rainbow I have been mentioning, consider what usually happens in darkened rooms, where a wall, or other body conveniently situated within, may so reflect the colours of bodies without the room, that they may very clearly be discerned and distinguished and yet it is taken for granted, that the colours seen in a darkened room, though they leave no traces of themselves upon the wall or body that receives them, are the true colours of the external objects, together with which the colours of the images are moved, or do rest. And the error is not in the eye, whose office is only to perceive the appearances of things, and which does truly so; but in the judging, or estimative faculty, which mistakingly concludes that colour to belong, to the wall, which does indeed belong to the object, because the wall is that from whence the beams of light, that carry the visible species, do come in strait lines directly to the eye: as for the same reason we are wont, at a certain distance from concave spherical glasses, to persuade ourselves, that we see the image come forth to meet us, and hang in the air betwixt the glass and us, because the reflected beams, that compose the image cross in that place where the image seems to be, and thence, and not from the glass, do in direct lines take their course to the eye. And upon the like cause it is, that divers deceptions in sounds and other sensible objects do depend, as we elsewhere declare.

5. I KNOW not whether I need add, that I have purposely tried (as you will find some pages hence, and will perhaps think somewhat strange) that colours, that are called emphatical, because not inherent in the bodies in which they appear, may be compounded with one another, as those that are confessedly genuine may. But when all this is said, Pyrophilus, I must advertise you, that it is but problematically spoken; and that though I think the opinion I have endeavoured to fortify probable, yet a great part of our discourse concerning colours may be true, whether that opinion be so or not.

1. THERE are, you know, Pyrophilus, besides those obsolete opinions about colours, which have been long since rejected, very various theories, that have each of them, even at this day, eminent men for their abettors: for the Peripatetic schools, though they dispute amongst themselves divers particulars concerning colours, yet in this they seem unanimously enough to agree, that colours are inherent and real qualities, which the light doth but disclose, and not concur to produce. Besides, there are moderns, who with a slight variation adopt the opinion of Plato; and as he would have colour to be nothing but a kind of flame consisting of minute corpuscles, as it were darted by the object against the eye, to whose pores their littleness and figure made them congruous; so these would have colour to be an internal light of the more lucid parts of the object, darkened, and consequently altered by the various mixtures of the less luminous parts. There are also others, who, imitation of some of the antient Atomists, make colour not to be lucid steam but yet a corporeal effluvium issuing out of the coloured body; but the knowingest of these have of late reformed their hypothesis, by acknowledging and adding, that some external light is necessary to excite, and, as they speak, solicit these corpuscles of colour, as they call them, and bring them to the eye. Another and more principal opinion of the modern philosophers, to which this last named may by a favourable explication be reconciled, is that, which derives colours from the mixture of light and darkness, or rather light and shadows. And as for the Chymists, it is known, that the generality of them ascribe the origin of colours to the sulphureous principle in bodies; though I find, as I elsewhere largely shew, that some of the chiefest of them derive colours rather from salt than sulphur, and others from the third hypostatical principle, mercury. And as for the Cartesians, I need not tell you, that they, supposing the sensation of light to be produced by the impulse made upon the organs of sight, by certain extremely minute and solid globules, to which the pores of the air and other diaphanous bodies are pervious, endeavour to derive the varieties of colours from the various proportion of the direct progress or motion of these globules to their circumvolution or motion about their own center, by which varying proportion they are by this hypothesis supposed qualified to strike the optic nerve after several distinct manners, so as to produce the perception of differing colours.

2. BESIDES these six principal hypotheses, Pyrophilus, there may be some others, which though less known, may perhaps as well as these deserve to be taken into consideration by you; but that I should copiously debate any of them at present, I presume you will not expect, if you confider the scope of these papers, and the brevity I have designed in them; and therefore I shall at this time only take notice to you in the general of two or three things, that do more peculiarly concern the treatise you have now in your hands.

3. AND first, though the embracers of the several hypotheses I have been naming to you, by undertaking each sect of them to explicate colours indefinitely by the particular hypotheses they maintain, seem to hold it forth as the only needful theory about that subject; yet for my part I doubt, whether any one of all these hypotheses have a right to be admitted exclusively to all others: for I think it probable, that whiteness and blackness may be explicated by reflection alone without refraction, as you will find endeavoured in the discourse you will meet with ere long, of the origin of whiteness and blackness; and on the other side, since I have not found, that by any mixture of white and true black (for there is a blueish black, which many misstake for a genuine) there can be a blue, a yellow, or a red, to name no other colours, produced; and since we do find, that these colours may be produced in the glass prism and other transparent bodies, by the help of refractions, it seems, that refraction is to be taken in, into the explication of some colours, to whose generation they seem to concur, either by making a further or other commixture of shades with the refracted light, or by some other way not now to be discoursed. And as it seems not improbable, that in case the pores of the air, and other diaphanous bodies be every where almost filled with such globuli, as the Cartesians suppose, the various kinds of motion of these globuli may in many cases have no small stroke in varying our perception of colour; So without the supposition of these globuli, which it is not so easy to evince, I think we may probably enough conceive in general, that the eye may be variously affected, not only by the entire beams of light that fall upon it, as they are such; but by the order, and by the degree of swiftness, and in a word, by the manner, according to which the articles that compose each particular beam arrive at the sensory so that whatever be the figure of the little corpuscles, of which the beams of light consist, not only the celerity or slowness of their revolution or rotation, in reference to their progressive motion, by their more absolute celerity, their direct undulating motion, and other accidents, which may attend their appulse to the eye, may fit them to make differing impressions on it.

4. SECONDLY, For these and the like considerations, Pyrophilus, I must desire, that you would look upon this little treatise, not as a discourse written principally to maintain any of the fore-mentioned theories, exclusively to all others, or substitute a new one of my own; but as the beginning of a history of colours, upon which, when you and your ingenious friends shall have enriched it, a solid theory may be safely built. But yet because this history is not meant barely for a register of the things recorded in it, but for an apparatus to a found and comprehensive hypothesis, I thought fit so to temper the whole discourse, as to make it as conducible as conveniently I can to that end: and therefore I have not scrupled to let you see, that I was willing to save you the labour of cultivating some theories, that I thought would never enable you to reach the ends you aim at, so to contract your enquiries into a narrow compass. For both which purposes I thought it requisite to do these two things; the one, to set down some experiments, which by the help of the reflections and insinuations that attend them, may assist you to discover the infirmness and insufficiency both of the common Peripatetic doctrine, and of the now more applauded theory of the chymists about colour; because these two doctrines having possessed themselves, the one of the most part of the schools, and the other of the esteem of the generality of physicians and other learned men, whose professions and ways of study do not exact, that they should scrupulously examine the very first and simplest principles of nature: I feared it would be to little purpose, without doing something to discover the insufficiency of these hypotheses, that I should (which was the other thing I thought requisite for me to do) set-down among my other experiments those in the greatest number, that may let you see, that, till I shall be better informed, I incline to take colour to be a modification of light; and would invite you chiefly to cultivate that hypothesis, and improve it to the making out of the generation of particular colours, as I have endeavoured to apply it to the explication of whiteness and blackness.

5. THIRDLY, But Pyrophilus, though this be at present the hypothesis I prefer, yet I propose it but in a general sense, teaching only, that the beams of light, modified by the bodies whence they are sent (reflected or refracted) to the eye, produce there that kind of sensation men commonly call colour. But whether I think this modification of the light to be performed by mixing it with shades, or by varying the proportion of the progress and rotation of the Cartesian Globuli Cœlestes, or by some other way, which I am not now to mention, I pretend not here to declare; much less do I pretend to determine, or scarce so much as to hope to know all that were requisite to be known, to give you, or even myself, a perfect account of the theory of vision and colours. For in order to such an undertaking, I would first know what light is, and if it be a body (as a body or the motion of a body it seems to be) what kind of corpuscles for size and shape it consists of, with what swiftness they move forwards, and whirl about their own centers. Then I would know the nature of refraction, which I take to be one of the abstrusest things (not to explicate plausibly, but to explicate satisfactorily) that I have met with in physicks. I would further know, what kind and what degree of commixture of darkness or shades is made by refractions, or reflections, or both, in the superficial particles of those bodies, that being shined upon, constantly exhibit the one, for instance, a blue, the other a yellow, the third a red colour. I would further know, why this contemperation of light and shade, that is made, for example, by the skin of a ripe cherry, should exhibit a red, and not a green, and the leaf of the same tree should exhibit a green rather than a red. And indeed, lastly, why since the light that is modified into these colours consists but of corpuscles moved against the retina or pith of the optic nerve, it should there not barely give a stroke, but produce a colour; whereas a needle wounding likewise the eye would not produce colour, but pain. These, and perhaps other things I should think requisite to be known, before I should judge myself to have fully comprehended the true and whole nature of colours: and therefore, though by making the experiments and reflections delivered in this paper, I have endeavoured somewhat to lessen my ignorance in this matter, and think it far more desirable to discover a little, than to discover nothing; yet I pretend but to make it probable by the experiments I mention, that some colours may be plausibly enough explicated in the general by the doctrine here proposed. For whensoever I would descend to the minute and accurate explication of particulars, I find myself very sensible of the great obscurity of things, without excepting those, which we never see but when they are enlightened, and confess with Scaliger, Latet natura hac (says he, speaking of that Colour) & ficut aliarum rerum species in profundissima caligne inseitiæ humane.

T H E

EXPERIMENTAL HISTORY

O F

C O L O U R S

C H A P. 1.

1. THOUGH after what I have acknowledged, Pyrophilus, of the abstruse nature of colours in particular, you will easily believe, that I pretend not to give you a satisfactory account of whiteness and blackness; yet not wholly to frustrate your expectation of my offering something by way of specimen towards the explication of some colours in particular, I shall make choice of these as the most simple ones (and by reason of their mutual opposition the least hardly explicable) about which to present you my thoughts, upon condition you will take them at most to be my conjectures, not my opinions.

2. WHEN I applied myself to confider, how the cause of whiteness might be explained by intelligible and mechanical principles, I remembered not to have met with any thing among the antient corpuscularian philosophers, touching the quality we call whiteness, Save that Democritus is by Aristotle said to have ascribed the whiteness of bodies to their smoothness, and on the contrary their blackness to their asperity. (Album quipped & nigrum, hoc quidem asperum esse dicit, hoc verò læve.-De sensu & sensil 3.) But though about the latter of those qualities his opinion be allowable, as we shall anon; yet that he needs a favourable interpretation in what is delivered concerning the first (at least if his doctrine be not misrepresented in this point, as it has been in many others) we shall quickly have occasion to manifest. But amongst the Moderns, the most learned Gassendus in his ingenious epistle published in the year 1642, De apparente magnitudine folis humilis & sublimis, reviving the atomical philosophy, has, though but incidentally, delivered something towards the explication of whiteness upon mechanical principles. And because no man that I know of, has done so before him, I shall, to be sure to do him right, give you his sense in his own words: (Epist. 2. page 45).

3. BUT though in this passage, that very ingenious person has anticipated part of what I should say; yet I presume you will for all that expect, that I should give you a fuller account of that notion of whiteness, which I have the least exceptions to, and of the particulars whence I deduce it; which to do, I must mention to you the following experiments and observations.

WHITENESS then considered as a quality in the object seems chiefly to depend upon this, that the superficies of the body, that is called white, is asperated by almost innumerable small surfaces; which being of an almost specular nature, are also so placed, that some looking this way, and some that way, they yet reflect the rays of light that fall on them, not towards one another, but outwards towards the spectator's eye. In this rude and general account of whiteness, it seems that besides those qualities, which are common to bodies of other colours, as for instance the minuteness and number of the superficial parts, the two chief things attributed to bodies as white are made to be, first, that little protuberances and superficial parts be of somewhat a specular nature, that they may, as little looking-glasses, each of them reflect the beams it receives (or the little picture of, the sun made on it) without otherwise considerably altering them; whereas in most other colours, they are wont to be much changed, by being also refracted, or by being returned to the eye, mixt with shades or otherwise. And next, that its superficial parts be so situated, that they retain not the incident rays of light by reflecting them inwards, but send them almost all back; so that the outermost corpuscles of a white body, having their various little surfaces of a specular nature, a man can from no place behold the body, but that there will be among those innumerable superficieculæ, that look some one way, and some another, enough of them obverted to his eye, to afford, like a broken looking-glass, a confused idea, or representation of light, and make such an impression on the organ, as that for which men are wont to call a body white. But this motion will perhaps be best explained by the same experiments and observations, on which it is built, and therefore I shall now advance to them.

4. AND in the first place I consider; that the sun, and other powerfully lucid bodies, are not only wont to offend, which we call to dazzle our eyes; but that if any colour be to be ascribed to them as they are lucid, it seems it should be whiteness. For the sun at noon-day, and in clear weather, and when his face is less troubled, and as it were stained by the steams of sublunary bodies, and when his beams have much less of the atmosphere to traject in their passage to our eyes, appears of a colour more approaching to white, than when nearer the horizon: the interposition of certain sorts of fumes and vapours make him oftentimes appear either red, or at least more yellow. And when the sun shines upon that natural looking-glass, a smooth water, that part of it, which appears to this or that particular beholder the most shined on, does to his eye seem far whiter than the rest. And here I shall add, that I have sometimes had the opportunity to observe a thing, that may make to my present purpose, namely, that when the sun was veiled over as it were, with a thin white cloud, and yet was too bright to be looked upon directly without dazzling, by casting my eyes upon a smooth water, as we sometimes do to observe eclipses without prejudice to our eyes, the sun then not far from the meridian appeared to me not red, but so white, that it was not without some wonder, that I made the observation. Besides, though we in English are wont to say, a thing is red-hot, as an expression of its being superlative ignitum (if I may so speak for want of a proper English word) yet in the forges of smiths, and the furnaces of other artificers, by that which they call a white heat, they mean a further degree of ignition, than by that which both they and we call a red heat.

5. SECONDLY, I consider, that common experience informs us, that as much light, overpowers the eye, so when the ground is covered with snow (a body extremely white) those that have weak eyes are wont to complain of too much light: and even those, that have not, are generally sensible of an extraordinary measure of light in the air; and if they are fain to look very long upon snow, find their sight offended by it. On which occasion we may call to mind what Xenophon relates, that his Cyrus marching his army for divers days through mountains covered with snow, the dazzling splendor of its whiteness prejudiced the sight of very many of his soldiers, and blinded some of them; and other stories of that nature may be met with in writers of good note. And the like has been affirmed to me by credible persons of my own acquaintance, and especially by one, who, though skilled in physic and not antient, confessed to me, when I purposely asked him, that not only during his stay in Muscovy he found his eyes much impaired, by being much reduced frequently to travel in the snow; but that the weakness of his eyes did not leave him when he left that country, but has followed him into these parts, and yet continues to trouble him. And to this doth agree what I as well as others have observed, namely, that when I travelled by night, when the ground was all covered with snow, through the night. otherwise would not have been lightsome, yet I could very well see to chuse my way. But much more remarkable to my present purpose is that, which I have met with in Olaus Magnus, concerning the way of travelling in winter in the Northern regions, where the days of that season are to very short: for after other things not needful to be here transcribed; Iter, says he, diurnum duo scilicet montana milliaria (quæ 12 Italica sunt) conficiunt. Nocte verò sub splendidissima luna, duplatum iter consumunt aut triplatum. Neque id incommodè fit, cum nivium reverberatione lunaris splendor sublimes & declives campos illustret, ac etiam montium præcipilia ac noxias feres à longs prospiciant evitandas

(Cent. Septent Histor, lib. 4 cap.13). Which testimony I the less scruple to allege, because it agrees very well with what has been affirmed to me by a physician of Muscow, whom the notion I have been treating of concerning whiteness invited me to ask, whether he could not see much farther, when he travelled by night in Russia than he could do in England, or elsewhere, when there was no snow upon the ground; for this ingenious person informed me, that he could see things at a far greater distance, and with more clearness, when he travelled by night on the Russian snow, though without the assistance of moon-shine, than we in these parts would easily be persuaded. Though it seems not unlikely to me, that the intenseness of the cold may contribute something to the considerableness of the effect, by much clearing the air of darkish steams, which in these more temperate climates are wont to thicken it in snowy weather: for having purposely enquired of this doctor, and consulted that ingenious navigator Captain James's voyage hereafter to be further mentioned, I find both their relations agree in this, that in dark frosty nights they could discover more stars, and see the rest clearer, than we in England are wont to do.

6. I KNOW indeed, that divers learned men think, that snow so strongly affects our eyes, not by a borrowed, but a native light; but I venture to give it as a proof, that white bodies reflect more light than others, because having once purposely placed a parcel of snow in a room carefully darkened, that no celestial light might come to fall upon it, neither I, nor an ingenious person (skilled in optics) whom I desired for a witness, could find, that it had any other light than what it received. And however, it is usual among those that travel in dark nights, that the guides wear something of white to be discerned by, there being scarce any night so dark, but that in the free air there remains some light, though broken and debilitated perhaps by a thousand reflections from the opacous corpuscles that swim in the air, and send it to one another before it comes to arrive at the eye.

7. THIRDLY, And the better to shew that white bodies reflect store of light, in comparison of those that are otherwise coloured, I did in the darkened room, formerly mentioned, hold not far from the hole, at which the light was admitted, a sheet only of white paper, from whence casting the sun-beams upon a white wall, whereunto it was obverted, it manifestly appeared both to me, and to the person I took for a witness of the experiment, that it reflected a far greater light, than any of the other colours formerly mentioned; the light so thrown upon the wall notably enlightning it, and by it a good part of the room. And yet further to shew you, that white bodies reflect the beams from them, and not towards themselves, let me add, that ordinary burning glass, such as are wont to be employed to light tobacco, will not in a great while burn, or so much as discolour a sheet of white paper. Insomuch that even when I was a boy, and loved to make trials with burning-glasses, I could not but wonder at this odd phenomenon, which set me very early upon guessing at the nature of whiteness; especially because I took notice, that the image of the sun upon a white paper was not so well defined (the light seeming too diffused) as upon black, and because I tried, that blacking over the paper with ink, not only the ink would be quickly dried up, but the paper, that I could not burn before, would be quickly set on fire. I have also tried, that my exposing my hand with a thin black glove over it to the warm sun, it was thereby very quickly and considerably more heated, than if I took off the glove, and held my hand naked, or put on it another glove of thin but white leather. And having thus shewn you, Pyrophilus, that white bodies reflect the most light of any, let us now proceed to confider, what is further to be taken notice of in them, in order to our present enquiry.

8. AND fourthly, whereas among the dispositions we attributed to white bodies, we also intimated this, that such bodies are apt, like speculums, though but imperfect ones, to reflect the light that falls on them untroubled or unstained, we shall, besides other particulars to be met with in these papers, offer you this in favour of the conjecture; that in the darkened room several times mentioned in this treatise, we tried, that the sun beams being cast from a coloured body upon a neighbouring white wall, the determinate colour of the body was from the wall reflected to the eye; whereas we could in divers cases manifestly alter the colour arriving at the eye, by substituting at a convenient distance, a (conveniently) coloured (and glossy) body, instead of the white wall as by throwing the beams from a yellow body upon a blue, there would be exhibited a kind of green, as in the experiments about colours is more fully declared.

9. I KNOW not whether I should on this occasion take notice, that when, as when looking upon the calm and smooth surface of a river betwixt my eye and the sun, it appeared to be a natural speculum, wherein that part, which reflected to my eye the entire and defined image of the sun, and the beams less remote from those which exhibited that image, appeared indeed of a great and whitish brightness, but the rest comparatively dark enough; if afterwards the superficies chanced to be a little, but not much troubled by a gentle breath of wind, and thereby reduced into a multitude of small and smooth speculums, the surface of the river would, suitably to the doctrine lately delivered, at a distance appear very much of kin to white, though it would lose that brightness or whiteness upon the return of the surface to calmness and an uniform level. And I have sometimes, for trial sake, brought by a lenticular glass the image of a river, shined upon by the sun, into an upper room darkened, and distant about a quarter of a mile from the river; by which means the numerous declining surfaces of the water appeared so contrasted, that upon the body, that received the images, the whole river appeared a very white object at two or three paces distance. But if we drew near it, this whiteness appeared to proceed from an innumerable company of lucid reflections, from the several gently waved superficies of the water, which looked near at hand like a multitude of very little, but shining scales of fish, of which many did every moment disappear, and as many were by the sun, wind and river generated anew. But though this observation seemed sufficiently to discover how the appearing whiteness in that case was produced, yet in some other cases water may have the same, though not so vivid a colour upon other accounts; for oftentimes it happens, that the smooth surface of the water does appear bright or whitish, by reason of the reflection not immediately of the images of the sun, but of the brightness of the sky; and in such cases a convenient wind may, where it passes along, make the surface look black, by causing many such furrows and cavities, as may make the inflected superficies of the water reflect the brightness of the sky rather inward than outward. And again, if the wind increase into a storm, the water may appear white, especially near the shore and the ship; namely because the rude agitation breaks it into foam or froth. So much do whiteness and blackness depend upon the disposition of the superficial parts of a body, to reflect the beams of light inward or outward. But that as white bodies reflect the most light of any, so their superficial particles are, in the sense newly delivered, of a specular nature; I shall now further endeavour to shew, both by the making of specular bodies white, and the making of a white body specular.

10. IN the fifth place then, I will inform you, that (not to repeat what Gassendus observes concerning water) I have for curiosity sake distilled quicksilver in a cucurbit, fitted with a capacious glass-head, and observed, that when the operation was performed by the degrees of fire requisite for my purpose, there would stick to the inside of the alembic a multitude of little round drops of mercury: and as you know, that mercury is a specular body, so each of these little drops was a small round, looking-glass; and a multitude of them lying thick and near one another, they did both in my judgment, and that of those invited to see it, make the glass they were fastened to, appear manifestly a white body. And yet, as I said, this whiteness depended upon the minuteness and nearness of the little mercurial globuli, the convexity of whose surfaces fitted them to represent in a narrow compass a multitude of little lucid images to differingly situated beholders. And here let me observe a thing, that seems much to countenance the notion I have been recommending; namely, that whereas divers parts of the sky, and especially the milky way, do to the naked, eye appear white (as the name itself imports) yet the galaxy looked upon through the telescope does not shew white, but appears to be made up of a vast multitude of little stars; so that a multitude of lucid bodies, if they be so small, that they cannot singly or apart be discerned by the eye, and if they be sufficiently thick set by one another, may by their confused beams appear to the eye one white body. And why is it not possible, that the like may be done, when a multitude of bright and little corpuscles being crowded together, are made to send together vivid beams to the eye, though they shine but, as the planets, by a borrowed light?

11. BUT to return to our experiments. We may take notice, that the white of an egg, though in part transparent, yet by its power of reflecting some incident rays of light, is in some measure a natural speculum, being long agitated with a whisk or spoon, loses its transparency, and becomes very white, by being turned into froth, that is, into an aggregate of numerous small bubbles, whose convex superficies fits them to reflect the light every way outwards. And it is worth noting, that when water, for instance, is agitated into froth, if the bubbles be great and few, the whiteness will be but faint, because the number of specula within a narrow compass is but small, and they are not thick set enough to reflect so many little images or beams of the lucid body, as are requisite to produce a vigorous sensation of whiteness. And partly, lest it should be said, that the whiteness of such globulous particles proceeds from the air included in the froth (which to make good, it should be proved that the air itself is white); and partly, to illustrate the better the notion we have proposed of whiteness, I shall add, that I purposely made this experiment: I took a quantity of fair water, and put to it, in a clear glass phial, a convenient quantity of oil or spirit of turpentine, because that liquor will not incorporate with water, and yet is almost as clear and colourless as it. These being gently shaken together, the agitation breaks, the oil (which, as I said, is indisposed to mix like wine or milk per minima with the water) into a multitude of little globes, which each of them reflecting outwards a lucid image, make the imperfect mixture of the two liquors appear whitish; but if by vehemently shaking the glass, for a competent time, you make a further comminution of the oil into far more numerous and smaller globuli, and thereby confound it also better with the water, the mixture will appear of a much greater whiteness, and almost like milk: whereas if the glass be a while let alone, the colour will by degrees impair, as the oily globes grow fewer and bigger, and at length will quite vanish, leaving both the liquors distinct and diaphanous as before. And such a trial hath not ill succeeded, when instead of the colourless oil of turpentine, I took a yellow mixture made of a good proportion of crude turpentine dissolved in that liquor and (if, I mis-remember not) it also succeeded better than one would expect, when I employed an oil brought by filings of copper, infused in it, to a deep green. And this (by the way) may be the reason, why oftentimes when the oils of some spices and of aniseeds, &c. are distilled in a limbec with water, the water (as I have several times observed) comes over whitish, and will perhaps continue so for a good while; because if the fire be made too strong,. the subtile chymical oil is thereby much agitated and broken, and blended with the water in such numerous and minute globules, as cannot easily in a short time emerge to the top of the water, and whilst they remain in it, make it, for the reason newly intimated, look whitish. And perhaps upon the same ground a cause may be rendered why hot water is observed to be usually more opacous and whitish, than the same water cold; the agitation turning the more spirituous or otherwise conveniently disposed particles of the water into vapours, thereby producing in the body of the liquor a multitude of small bubbles, which interrupt the free passage, that the beams of light would else have every way, and from the innermost parts of the water reflect many of them outwards. These and the like examples, Pyrophilus, have induced me to suspect that the superficial particles of white bodies may for the most part be as well convex as smooth: I content myself to say, suspect and for the most part, because it seems not easy to prove, that when diaphanous bodies, as we shall see by and by, are reduced into white powders, each corpuscle must needs be of a convex superficies, since perhaps it may suffice that specular surfaces look several ways. For (as we have seen) when a diaphanous body comes to be reduced to very minute parts, it thereby acquires a multitude of little surfaces within a narrow compass. And though each of these should not be of a figure convenient to reflect a round image of the sun, yet even from such an inconveniently figured body there may be reflected some (either straight or crooked) physical line of light; which line I call physical, because it has some breadth in it, and in which line in many cases some refracttion of the light falling upon the body it depends on may contribute to the brightness: as if a slender wire, or solid cylinder of glass, be exposed to the light, you shall see in some part of it a vivid line of light and if we were able to draw out and lay together a multitude of these little wires or thrids of glass, so slender, that the eye could not discern a distance betwixt the luminous lines, there is little doubt (as far as I can guess by a trial purposely made with very slender, but far less slender thrids of glass, whose aggregate was looked upon one way white) but the whose physical superficies composed of them would to the eye appear white; and if so, it will not be always necessary that the figure of those corpuscles, that make a body appear white, should be globulous. And as for snow itself, though the learned Gassendus (as we have seen above) makes it to seem nothing else but a pure frozen froth, consisting of exceedingly minute and thick-set bubbles, yet I see no necessity of admitting that, since not only by the variously and curiously figured snow, that I have divers times had the opportunity with pleasure to observe, but also by the common snow, it rather doth appear both to the naked eye, and in a microscope, often, if not most commonly, to consist principally of little slender icicles of several shapes, which afford such numerous lines of light, as we have been newly speaking of.

12. SIXTHLY, If you take a diaphanous body as for instance a piece of glass, and reduce it to powder, the same body, which, when it was entire, freely transmitted the beams of light, acquiring by contusion a multitude of minute surfaces, each of which is as it were a little, but imperfect speculum, is qualified to reflect, in a confused manner, so many either beams, or little and singly unobservable images of the lucid body, that from a diaphanous it degenerates into a white body. And I remember I have for trial's sake taken lumps of rock crystal, and heating them red-hot in a crucible, I found, according to my expectation, that being quenched in fair water, even those, that remained in seemingly entire lumps, exchanged their tranflucency for whiteness, the ignition and extinction having as it were cracked each lump into a multitude of minute bodies, and thereby given it a great multitude of new surfaces. And even with diaphanous bodies, that are coloured, there may be this way a greater degree of whiteness produced, than one would lightly think -, as I remember, I have by contusion obtained whitish. powders of granates, glass of antimony, and emeralds finely beaten; and you may more easily make the experiment, by taking good venereal vitriol of a deep blue, and comparing with some of the entire crystals purposely reserved some of the subtile powder of the same salt, which will comparatively exhibit a very considerable degree of whiteness.

13. SEVENTHLY, And as by a change of position in the parts, a body that is not white may be made white; so by a slight change of the texture of its surface, a white body may be deprived of its whiteness. For if (as I have tried in goldsmiths shops) you take a piece of silver, that has been freshly boiled, as the artificers call it (which is done by first brushing, and then decocting it with salt and tartar, and perhaps some other ingredients) you shall find it to be of a lovely white. But if you take a piece of smooth steel, and therewith burnish a part of it, which may be presently done, you shall find, that part will lose its whiteness, and turn a speculum, looking almost every where dark, as other looking-glasses do; which may not a little confirm our doctrine. For by this we may guess, what it is chiefly that made the body white before, by considering that all, that was done to deprive it of that whiteness, was only to depress the little protuberances, that were before on the surface of the silver, into one continued superficies, and thereby effect this, that now the image of the lucid body, and consequently a kind of whiteness shall appear to your eye; but in some place of the greater silver looking-glass (whence the beams reflected at an angle equal to that wherewith they fall on it, may reach your eye) whilst the asperity remained undestroyed, the light failing on innumerable little specula obverted some one way, and some another, did from all sensibly distinguishable parts of the superficies reflect confused beams or representations of light to the beholder's eye, from whence soever he chance to look upon it. And among the experiments annexed to this discourse, you will find one, wherein, by the change of texture in bodies, whiteness is in a trice both generated and destroyed.

1. WHAT we have discoursed of whiteness, may somewhat assist us to form a notion of blackness, those two qualities being contrary enough to illustrate each other. Yet among the antient philosophers I find less assistance to form a notion of blackness than of whiteness; only Democritus in the passage above recited out of Aristotle has given a general hint of the cause of this colour, by referring the blackness of bodies to their asperity, But this I call. but a general hint, because those bodies that are green, and purple, and blue, seem to be so, as well as black ones, upon. the account of their superficial asperity. But among the moderns, the formerly mentioned Gassendus, perhaps invited by this hint of Democritus, has incidentally in another epistle given us, though a very short, yet a somewhat clearer account of the nature of blackness in these words:

I wish this ingenious man had enlarged himself upon this subject; for indeed it seems, that as that, which makes a body white, is chiefly such a disposition of its parts, that it reflects (I mean without much interruption) more of the light that falls on it, than bodies of any other colour do; so that, which makes a body black, is principally a peculiar kind of texture, chiefly of its superficial particles, whereby it does as it were dead the light that falls on it, so that very little is reflected outwards to the eye.

2. AND this texture may be explicated two, and perhaps more than two several ways; whereof the first is by supposing in the superficies of the black body a particular kind of asperity, whereby the superficial particles reflect but few of the incident beams outwards, and the rest inwards towards the body itself. As if, for instance, we should conceive the surface of a black body to be asperated by an almost numberless throng of little cylinders, pyramids, cones, and other such corpuscles, which, by their being thick set and erected, reflect the beams of light from one to another inwards, and send them to and fro so often, that at length they are lost, before they can come to rebound out again to the eye. And this is the first of the two mentioned ways of explicating blackness. The other way is by supposing the texture of black bodies to be such, that either by their yielding to the beams of light, or upon some other account, they do as it were dead the beams of light, and keep, them from being reflected in any plenty, or with any considerable vigour or motion, outwards. According to this notion it may be said, that the corpuscles, that make up the beams of light, whether they be solary effluviums, or minute particles of some ætherial substance, thrusting on one another from the lucid body, do, falling on black bodies, meet with such a texture, that such bodies receive into themselves, and retain almost all the motion communicated to them by the corpuscles that make up the beams of light, and consequently reflect but few of them, or those but languidly, towards the eye; it happening here almost in like manner as to a ball, which thrown against a stone or floor would rebound a great way upwards, but rebounds very little or not at all, when it is thrown against water, or mud, or a loose net, because the parts yield, and receive into themselves the motion, on whose account the ball should be reflected outwards. But this last way of explicating blackness I shall content myself to have proposed, without either adopting it, or absolutely rejecting it. For the hardness of touch-stones, black marble, and other bodies, that being black are solid, seem to make it somewhat improbable, that such bodies should be of so yielding a texture, unless we should say, that some bodies may be more disposed to yield to the impulses of the corpuscles of light by reason of a peculiar texture, than other bodies, that in other trials appear to be softer than they. But though the former of these two explications of blackness be that, by which we shall endeavour to give an account of it; yet, as we said, we shall not absolutely reject this latter, partly because they both agree in this, that black bodies reflect: but little of the light that falls on them, and partly because it is not impossible, that in some cases both the disposition of the superficial particles, as to figure and position, and the yielding of the body, or some of its parts, may jointly, though not in an equal measure concur to the rendering of a body black. The considerations, that induced me to propose this notion of blackness, as I explained it, are principally these:

3. FIRST, That as I lately said, whiteness and blackness being generally reputed to be contrary qualities, whiteness depending, as I said, upon the disposition of the parts of a body to reflect much light, it seems likely, that blackness may depend upon a contrary disposition of the black bodies surface; but upon this I shall not insist.

4. NEXT then we see, that if a body of one and the same colour be placed, part in the sun-beams, and part in the shade, that part which is not shined on will appear more of kin to blackness than the other, from which more light rebounds to the eye; and dark colours seem the blacker, the less light they are looked upon in; and we think all things black in the dark, when they send no beams to make impressions on our organs of sight: so that shadows and darkness are near of kin, and shadow, we know, is but a privation of light: and accordingly blackness seems to proceed from the paucity of beams reflected from the black body to the eye; I say, the paucity of beams, because those bodies, that we call black, as marble, jett, &c. are short of being perfectly so, else we should not see them at all. But though the beams, that fall on the sides of those erected particles, that we have been mentioning, do few of them return outwards, yet those, that fall upon the points of those cylinders, cones, or pyramids, may thence rebound to the eye, though they make there but a faint impression, because they arrive not there, but mingled with a great proportion of little shades. This may be confirmed by my having procured a large piece of black marble well polished, and brought to the form of a large spherical and concave speculum; for on the inside this marble being well polished, was a kind of dark looking-glass, wherein I could plainly see a little image of the sun, when that shined upon it. But this image was very far from offending and dazzling my eyes, as it would have done from another speculum; nor, though the speculum were large, could I in a long time, or in a hot sun, set a piece of wood on fire, though a far less speculum of the same form, and of a more reflecting matter, would have made it flame in a trice.

5. AND on this occasion we may as well in reference to something formerly delivered concerning whiteness, as in reference to what has been newly said, subjoin what we further observed touching the differing reflections of light from white and black marble; namely, that having taken a pretty large mortar of white marble, new, and polished in the inside, and exposed it to the sun, we found, that it reflected a great deal of glaring light, but so dispersed, that we could not make the reflected beams concur in any such conspicuous focus, as that newly taken notice of in the black marble; though perhaps there may enough of them be made to meet near the bottom, to make some kind of focus, especially since by holding in the night-time a candle at a convenient distance, we were able to procure a concourse of some, though not many of the reflected beams, at about two inches distant from the bottom of the mortar: but we found the heat even of the sun-bearns so dispersedly reflected to be very languid, even in comparison of the black marble's focus. And the little pictures of the sun, that appeared upon the white marble as a speculum, was but very faint and exceeding ill defined. Secondly, that taking two pieces of plain and polished surfaces, and casting on them successively the beams of the same candle, in such manner, as that the neighbouring superficies being shaded by an opacous and perforated body, the incident beams were permitted to pass but through a round hole of about half an inch diameter, the circle of light, that appeared on the white marble, was in comparison very bright, but very ill defined; whereas that on the black marble was far less luminous, but much more precisely defined.

6. THIRDLY, when you look upon a piece of linen, that has small holes in it, those holes appear very black, and men are often deceived in taking holes for spots of ink; and painters, to represent holes, make use of black; the reason of which seems to be, that the beams, that fall on those holes, fall into them so deep, that none of them is reflected back to the eye. And in narrow wells part of the mouth seems black, because the incident beams are reflected downwards from one side to another, till they can no more rebound to the eye.

WE may consider too, that if differing parts of the same piece of black velvet be stroaked opposite ways, the piece of velvet will appear of two distinct kinds of blackness, the one far darker than the other; of which disparity the reason seems to be, that in the less obscure part of the velvet, the little silken piles, whereof it is made up, being inclined, there is a greater part of each of them obverted to the eye; whereas in the other part the piles of silk being more erected, there are far fewer beams reflected outwards from the lateral parts of each pile; so that most of those, that rebound to the eye, come from the tops of the piles, which make but a small part of the whole superficies, that may be covered by the piece of velvet. Which explication I propose, not that I think the blackness of the velvet proceeds from the cause assigned, since each single pile of silk is black by reason of its texture, in what position soever you look upon it; but that the greater blackness of one of these tufts seems to proceed from the greater paucity of beams reflected from it, and that from the fewness of those parts of a surface, that reflect beams, and the multitude of those shaded parts that reflect none. And I remember, that I have oftentimes observed, that the position of particular bodies far greater than piles of silk in reference to the eye, may, notwithstanding their having each of them a colour of its own, make one part of their aggregate appear far darker than the other; for I have near great towns often take notice, that a cart-load of carrots packed up appeared of a much darker colour when looked upon, where the points of the carrots were obverted to the eye, than where the sides of them were so.

7. FOURTHLY, in a darkened room, I purposely observed, that if the sun-beams, which came in at the hole, were received upon white or any other colour, and directed to a convenient place of the room, they would manifestly, though not all equally, increase the light of that part; whereas if we substituted, either a piece of black cloth or black velvet, it would so dead the incident beams, that the place (newly mentioned) whereto I obverted the black body, would be less enlightened than it was before, when it received its light but from the weak and oblique reflecttions of the floor and walls of a pretty large room, through which the beams, that came in at the hole, were confusedly and brokenly dispersed.

8. FIFTHLY, And to shew, that the beams, that fall on black bodies, as they do not rebound outwards to the eye, so they are reflected towards the body itself, as the nature of those erected particles, to which we have imputed blackness requires, we will add an experiment, that will also confirm our doctrine touching whiteness namely, that we took a broad and large tile, and having whitened over one half of the superficies of it, and blacked the other, we exposed it to the summer's sun; and having let it lie there a convenient time (for the difference is more apparent, if it have not lain there too long) we found, as we expected, that whilst the whited part of the tile remained cool enough, the blacked part of the same tile was grown not only sensible, but very hot (sometimes to a strong degree.) And to satisfy some of our friends the more, we have sometimes left upon the surface of the tile, besides the white and black parts thereof, a part, that retained the native red of the tile itself and exposing them to the sun, we observed this last mentioned to have contracted a heat in comparison of the white, but a heat inferior to that of the black; of which the reason seems to be, that the superficial particles of black bodies, being, as we said, more erected, than those of white or red ones, the corpuscles of light falling on their sides, being for the most part reflected inward from one particle to another, and thereby engaged as it were, and kept from rebounding upwards, they communicate their brisk motion, wherewith they were impelled against the black body (upon whose account, had they they fallen upon a white body, they would have been reflected outwards) to the small parts of the black body, and thereby produce in those small parts such an agitation, as (when we feel it) we are wont to call heat. I have been lately informed, that an observation near of kin to ours has been made by some learned men in France and Italy, by long exposing to a very hot sun two pieces of marble, the one white and the other black. But though the observation be worthy of them, and may confirm the same truth with our experiment, yet besides that our trial needs not the summer, nor any great heat to succeed, it seems to have this advantage above the other, that whereas bodies more solid, and of a closer texture, though they use to be more slowly heated, are wont to receive a greater degree of heat from the sun or fire, than (cæteris paribus) bodies of a slighter texture. I have found by the information of stone-cutters, and by other ways of enquiry, that black marble is much solider and harder than white; so that possibly the difference betwixt the degrees of heat, they receive from the sun-beams, will by many be ascribed to the difference of their texture, rather than to that of their colour; though I think our experiment will make it probable enough, that the greater part of that difference may well be ascribed to that disposition of parts, which makes the one reflect the sun-beams inward, and the other outwards. And with this doctrine accords very well, that rooms hung with black are not only darker than else they would be, but are wont to be warmer too; insomuch that I have known a great lady, whose constitution whas somewhat tender, complain, that she was wont to catch cold, when she went out into the air, after having made any long visits to persons, whose rooms were hung with black. And this is not the only lady I have heard complain of the warmth of such rooms; which though perhaps it may be partly imputed to the effluvia of those materials, wherewith the hangings were dyed, yet probably the warmth of such rooms depends chiefly upon the same cause, that the darkness does; as (not to repeat what I formerly noted touching my gloves) to satisfy some curious persons of that sex, I have convinced them, by trial, that of two pieces of silken stuff given to me by themselves, and exposed in their presence to the same window, shined on by the sun, the white was considerably heated, when the black was not so much as sensibly so.

9. SIXTHLY, I remember, that acquainting one day a Virtuoso of unsuspected credit, that had visited hot countries, with part of what I have here delivered concerning blackness, he related to me, by way of confirmation of it, a very notable experiment, which he had both seen others make, and made himself in a warm climate; namely, that having carefully blacked over eggs, and exposed them to the hot sun, they were thereby in no very long time well roasted; to which effect I conceive the heat of the climate must have concurred with the disposition of the black surface to reflect the sun-beams inward: for I remember, that having made that among other trials in England, though in summer-time, the eggs I exposed acquired indeed a considerable degree of heat, but yet not so intense a one, as proved sufficient to roast them.

10. SEVENTHLY, and lastly, our conjectures at the nature of blackness may be somewhat confirmed by the (formerly mentioned observation of the blind Dutchman, that discerns colours with his fingers; for he says, that he feels a greater roughness upon the surfaces of black bodies, than upon those of red, or yellow, or green. And I remember, that the diligent Bartholinus says, that a blind Earl of Mansfield could distinguish white from black only by the touch; which would sufficiently argue a great disparity in the asperities, or other superficial textures of bodies of those two colours, if the learned relator had affirmed the matter upon his own knowledge.

11.THESE, Pyrophilus, are the chief things, that occur to me at present, about the nature of whiteness and blackness; which if they have rendered it so much as probable, that in most, or at least many cases, the causes of these qualities may be such as I have adventured to deliver, it is as much as I pretend to. For till I have opportunity to examine the matter by some further trials, I am not sure, but that in time white and black bodies, there may concur to the colour some peculiar texture or disposition of the body, whereby the motion of the small corpuscles, that make up the incident beams of light, may be differingly modified, before they reach the eye especially in this, that white bodies do not only copiously reflect those incident corpuscles outwards, but reflect them briskly, and do not otherwise alter them in the manner of their motion. Nor shall I now stay to inquire, whether some of those other ways (as a disposition alter the velocity, the rotation, or the order and manner of appulse to the eye of the reflected corpuscles, that composed the incident beams of light) which we mentioned, when we considered the production of colours in general, may not in some cases be applicable to those of white and black bodies: for I am yet so much a seeker in this matter, and so little wedded to the opinions I have proposed, that what I am to add, shall be but the beginning of a collection of experiments and observations towards the history of whiteness and blackness, without at present interposing my explications of them; that so I may assist your enquiries, without much forestalling or byassing your judgment.

EXPERIMENT in CONSORT,

HAVING promised in the 27th page of the foregoing discourse of whiteness and blackness, to shew, that those two colours may, by a change of texture in bodies, each of them apart diaphanous and colourless, be at pleasure and in a trice as well generated as destroyed, we shall begin with experiments, that may acquit us of that promise.

TAKE then what quantity you please of fair water, and having heated it, put into it as much good common sublimate, as it is able to dissolve, and (to be sure of having it well glutted) continue putting in the sublimate, till some of it lie untouched in the bottom of the liquor. Filter this solution through cap-paper, to have it clear and limpid, and into a spoonful or two thereof (put into a clean glass-vessel) shake about four or five drops (according as you took more or less of this solution) of good limpid spirits of urine, and immediately the whole mixture will appear white like milk; to which mixture if you presently add a convenient proportion of rectified aqua fortis (for the number of drops is hard to determine, because of the differing strength of the liquor, but easily found by trial) the whiteness will presently disappear, and the whole mixture become transparent; which you may, if you please, again reduce to a good degree of whiteness (though inferior to the first) only by a more copious affusion of fresh spirit of urine. N. B. First, that it is not so necessary to employ either aqua fortis or spirit of urine about this experiment, but that we have made it with other liquors instead of these; of which perhaps more elsewhere. Secondly, that this experiment, though not made with the same menstruums, nor producing the same colour, is yet much of kin to that other to be mentioned in this tract, among our other experiments of colours, about turning a solution of precipitate into an orange colour; and the chymical reason being much alike in both, the annexing it to one of them may suffice for both.

MAKE a strong infusion of broken galls in fair water; and having filtered it into a clean phial, add more of the same liquor to it, till you have made it somewhat transparent, and sufficiently diluted the colour, for the credit of the experiment, lest otherwise the darkness of the liquor might make it be objected, that it was already almost ink. Into this infusion shake a convenient quantity of a clear, but very strong solution of vitriol; and you shall immediately see the mixture turn black almost like ink, and such a way of producing blackness is vulgar enough; but if presently after you do upon this mixture drop a small quantity of good oil of vitriol, and, by shaking the phial, disperse it nimbly through the two other liquors, you shall (if you perform your part well, and have employed oil of vitriol clear and strong enough) see the darkness of the liquor presently begin to be discussed, and grow pretty clear and transparent, losing its inky blackness, which you may again restore to it by the affusion of a small quantity of a very strong solution of salt of tartar, And though neither of these atramentous liquors will seem other than very pale ink, if you write with a clean pen dipt in them; yet that is common to them with some sorts of ink, that prove very good when dry; as I have also found, that when I made these carefully, what I wrote with either of them, especially with the former, would, when thoroughly dry, grow black enough not to appear bad ink. This experiment of taking away, and restoring blackness from and to the liquors, we have likewise tried in common ink; but there it succeeds not so well, and but very slowly, by reason that the gum wont to be employed in the making it does by its tenacity oppose the operations of the above-mentioned saline liquors. But to consider gum no more, what some kind of precipitation may have to do in the producing and destroying the inks without it, I have elsewhere given you some occasion and assistance to inquire: but I must not now stay to do so myself, only I shall take notice to you, that though it be taken for granted, that bodies will not be precipitated by alcalizate salts, that have not first been dissolved in some acid menstruums; yet I have found upon trials, which my conjectures led me to make on purpose, that divers vegetables, barely infused, or, but slightly decocted in common water, would, upon the affusion. of a strong and clear lixivium of pot-ashes, and much more of some other precipitating liquors that I sometimes employ, afford good store of a curdled matter, such as I have had in the precipitations of vegetable substances, by the intervention of acid things; and that this matter was easily separable from the rest of the liquor, being left behind it in the filtre. And in making, the first ink mentioned in this experiment, I found, that I could by filtration separate pretty store of a0 black pulverable substance, that remained in the filtre; and when the ink was made clear again by the oil of vitriol, the affusion of dissolved sal tartari seemed but to precipitate, and thereby to unite and render conspicuous the particles of the black mixture, that had before been dispersed into very minute and singly invisible particles by the incisive and resolving power of the highly corrosive oil of vitriol.

AND to manifest, Pyrophilus, that galls are not so requisite as many suppose to the making atramentous liquors, we have sometimes tried the following experiment: we took dried rose-leaves, and decocted them for a while in fair water; into two or three spoonfuls of this decoction we shook a few drops of a strong and well filtrated solution of vitriol (which perhaps, had it been green, would have done as well) and immediately the mixture did turn black, and when into this mixture, presently after it was made, we shook a just proportion of aqua fortis, we turned it from a black ink to a deep red one, which by the affusion of a little spirit of urine may be reduced immediately to an opacous and blackish colour. And in regard, Pyrophilas, that in the former experiments, both the infusion of galls, and the decoction of roses, and the solution of copperas, employed about them, are endowed each of them with its own colour, there may be a more noble experiment of the sudden production of blackness made by the way mentioned in the second section of the second part of our essays; for though upon the confusion of the liquors there mentioned, there do immediately emerge a very black mixture; yet both the infusion of orpiment and the solution of minimum were, before their being joined together, limpid and colourless.

IF pieces of white hartshorn be with a competent degree of fire distilled in a glass retort, they will, after the avolation of the phlegm, spirit, volatile salt, and the looser and the lighter parts of the oleaginous substance, remain behind of a coal black colour. And even ivory itself being skillfully burnt (how I am wont to do it, I have elsewhere set down) affords painters one of the best and deepest blacks they have. And yet in the instance of distilled hartshorn, the operation being made in glass vessils carefully closed, it appears there is no extraneous black substance, that insinuates itself into white hartshorn, and thereby makes it turn black; but that the whiteness is destroyed, and the blackness generated, only by a change of texture, made in the burnt body, by the recess of some parts, and the transposition of others. And though I remember not, that in many distillations of hartshorn I ever found the Cap. Mort. to pass from black to a true whiteness, whilst it continued in closed vessels; yet having taken out the coal-black fragments, and calcined them in open vessels, I could in few hours quite destroy that blackness, and without sensibly changing their bulk or figure, reduce them to great whiteness. So much do these two colours depend upon the disposition of the little parts, that the bodies, wherein they are to be met with, do consist of. And we find, that if white wine-tartar, or even the white crystals of such tartar be burnt without being truly calcined, the Cap. mortuum (as the chymists call the more fixt part) will be black. But if you further continue the calcination, till you have perfectly incinerated the tartar, and kept it long enough in a strong fire, the remaining calx will be white. And so we see, that not only other vegetable substances, but even white woods, as the hazel, will yield a black charcoal, and afterwards white ashes; and so animal substances naturally white, as bones and egg shells, will grow black upon the being burnt, and white again, when they are perfectly calcined.

BUT yet I much question, whether that rule delivered by divers, as well philosophers as chymists, adusta nigra, fed perusta alba, will hold as universally as is presumed, since I have several examples to allege against it. For I have found, that by burning alabaster, so as both to make it appear to boil almost like milk, and to reduce it to a very fine powder, it would not at all grow black, but retain its pure and native whiteness; and though by keeping it longer than is usual in the fire, I produced but a faint yellow, even in that part of the powder, that lay nearest the top of the crucible; yet having purposely inquired of an experienced stone-cutter, who is curious enough in trying conclusions in his own trade, he told me he had found, that if alabaster or plaster of Paris be very long kept in a strong fire, the whole heap of burnt powder would exchange its whiteness for a much deeper colour than the yellow I observed. Lead being calcined with a strong fire turns (after having perhaps run through divers other colours) into minium, whose colour we know is a deep red; and if you urge this minium, as I have purposely done with a strong fire, you may much easier find a glassy and brittle body darker than minium, than any white calx or glass. It is known among chymists, that the white calx of antimony, by the further and more vehement operation of the fire, may be melted into glass, which we have obtained of a red colour, which is far deeper than that of the calx of burnt antimony. And though common glass of antimony being usually adulterated with borax, have its colour thereby diluted, oftentimes to a very pale yellow; yet not only ours made more sincerely was, as we said, of a colour less remote from black, than was the calx; but we observed, that by melting it once or twice more, and so exposing it to the further operation of the fire, we had, as we expected. the colour heightened. To which we shall add but this one instance (which is worth the taking notice of, in reference to colours) that, if you take blue, but unsophisticated, vitriol, and burn it very slowly, and with a gentle degree of heat, you may observe, that when it is burnt but a little, and yet so far as that you may rub it to powder betwixt your fingers, it will be of a white or whitish colour; but if you prosecute the calcination, this body, which by a light adustion was made white, will pass through other colours, as gray, yellowish, and red; and if you further burn it with a long and vehement fire. By that time it comes to be perustum, it will be of a dark purple, nearer to black, not only than the first calx, but than the vitriol before it at all felt the fire. I might add, that Crocus Martis (per se, as they call it) made by the lifting violence of the reverberated flames is not so near a-kin to white, as the iron or steel that afforded it was before its calcinations; but that I suppose, these instances may suffice to satisfy you, that minerals are to be excepted out of the forementioned rule, which perhaps, though it seldom fail in substances belonging to the vegetable or animal kingdom, may yet be questioned even in some of these if that be true, which the judicious traveller Bellonius affirms, that charcoals made out of the wood of oxycedar are white: and I could not find, that though in retorts hart's-horn and other white bodies will be denigrated by heat, yet camphire would not at all lose its whiteness, though I have purposely kept it in such a heat, as made it melt and boil.

AND now I speak of camphire, it puts me in mind of adding this experiment, that though, as I said, in closed glasses I could not denigrate it by heat, but it would sublime to the sides and top of the glass, as it was before; yet not only it will, being set on fire in the free air, send forth a copious smoke, but having purposely upon some of it that was flaming, clapt a large glass, almost in the form of a hive (but more slender only) with a hole at the top (which I caused to be made to try experiments of fire and flame in) it continued so long burning, that it lined all the inside of the glass with a soot as black as ink, and so copious, that, the closeness of the vessel considered, almost all that part of the white camphire, that did take fire, seemed to have been changed into that deep black substance.

AND this also brings into my mind another experiment, that I made about the production of blackness, whereof, for reasons too long to be here deduced, I expected and found a good success; and it was this: I took rectified oil of vitriol (that I might have the liquor clean as well as strong) and by degrees mixt with it a convenient proportion of the essential oil, as chymists call it, of wormwood, drawn over with store of water in a limbec; and warily distilling the mixture in a retort, there remained a scarce credible quantity of dry matter, black as a coal. And because the oil of wormwood, though a chymical oil drawn by a Virtuoso, seemed to have somewhat in it of the colour of the plant, I substituted in its room the pure and subtile essential oil of winter-savory, and mixing little by little this liquor with (if I mis-remember not) an equal weight of the formerly mentioned rectified oil of vitriol, and distilling them as before in a retort, besides what there passed over into the receiver, even these two clear liquors left me a considerable proportion (though not so great as the two former) of a substance black as pitch, which I yet keep by me as a rarity.

A WAY of whiting wax cheaply and in great quantity may be a thing of good œconomical use; and we have elsewhere set down the practice of tradesmen that blanch it, but here treating of whiteness only, in order to the philosophy of colours, I shall not examine, which of the slow ways may be best employed, to free wax from the yellow melleous parts, but shall rather set down a quick way of making it white, though but in very small quantities. Take then a little yellow wax, scraped or thinly sliced, and putting it into a bolt's-head or some other convenient glass, pour to it a pretty deal of spirit of wine, and placing the vessel in warm sand, increase the heat by degrees, till the spirit of wine begin to simmer or to boil a little; and continuing that degree of fire, if you have put liquor enough, you will quickly have the wax dissolved: then taking it off the fire, you may either suffer it to cool as hastily as with safety to the glass you can, or pour it, whilst it is yet hot, into a filtre of paper; and either in the glass where it cools, or in the filtre, you will soon find the wax and menstruum together reduced into a white substance, almost like butter, which by letting the spirit exhale will shrink into a much lesser bulk, but still retaining its whiteness. And that which is pretty in the working of this magistery of wax, is, that the yellowness vanishes, neither appearing in the spirit of wine, that passes limpid through the filtre, nor in the butter of wax, if I may so call it, that, as I said, is white.

THERE is an experiment, Pyrophilus, which though I do not so exactly remember; and though it be somewhat nice to make, yet I am willing to acquaint you with, because the thing produced, though it be but a curiosity, is wont not a little to please the beholders; and it is away of turning, by the help of a dry substance, an almost golden-coloured concrete into a white one. The several trials are not at present so fresh in my memory to enable me to tell you certainly, whether an equal only or a double weight of common sublimate must be taken in reference to the tin-glass; but, if I mistake not, there was in the experiment, that succeeded best, two parts of the former taken to one of the latter. These ingredients being finely powdered and exactly mixed, we sublimed together by degrees of fire (the due gradation of which is in this experiment a thing of main importance;) there ascended a matter of a very peculiar texture; for it was for the most part made up of very thin, smooth, soft and slippery plates, almost like the finest sort of scales of fishes, but of so lovely a white inclining to pearl-colour, and of so curious a colour and shining a gloss, that they appeared in some respect little inferior to orient pearls, and in other regards, they seemed to surpass them, and were applauded for a sort of the prettiest trifles, that we had ever prepared to amuse the eye. I will not undertake, that though you will hardly miss changing the colour of your shining tin-glass, yet you will the first or perhaps the second time hit right upon the way of making the glistering sublimate I have been mentioning.

WHEN we dissolve in aqua fortis a mixture of gold and silver melted into one lump, it usually happens, that the powder of gold, that falls to the bottom, as not being dissoluble by that menstruum, will not have its own yellow, but appear of a black colour, though neither the gold, nor the silver, nor the aqua fortis did before manifest any blackness. And divers alchymists, when they make solutions of minerals they would examine, are very glad, if they see a black powder precipitated to the bottom, taking it for a hopeful sign, that those particles are of a golden nature, which appear in a colour so ordinary to gold parted from other metals by aqua fortis, that it is a trouble to the refiner to reduce the precipitated calx to its native colour. For though (as we have tried) that may be quickly enough done by fire, which will make this gold look very gloriously (as indeed it is at least one of the best ways, that is practised for the refining of gold) yet it requires both watchfulness and skill, to give it such a degree of fire, as will serve to restore it to its lustre, without giving it such a one, as may bring it to fusion, to which the minuteness of the corpuscles it consists of makes the powder very apt. And this brings into my mind, that having taken a flat and bright piece of gold, that was refined by a curious and skilful person on purpose to try to what height of purity gold could be brought by art, I found that this very piece, as glorious as it looked, being rubbed a little upon a piece of fine clean linen, did sully it with a kind of black: and the like I have observed in refined silver, which I therefore mention, because I formerly suspected that the impurity of the metal might have been the only cause of what I have divers times observed in wearing silver-hilted swords, namely, that where they rubbed upon my clothes, if they were of a light-coloured cloth, the affriction would quickly black them; and congruously hereunto I have found pens blacked almost all over, when I had a while carried them about me in a silver ink-case. To which I shall only add, that whereas in these several instances of denigration, the metals are worn off, or otherwise reduced into very minute parts, that circumstance may prove not unworthy your notice.

THAT a solution of silver does dye hair of a black colour, is a known experiment, which some persons, more curious than dexterous, have so, unluckily made upon themselves, as to make their friends very merry. And I remember, that the other day I made myself some sport by an improvement of this observation; for having dissolved some pure silver in aqua fortis, and, evaporated the menstuum ad siccitatem as they speak, I caused a quantity of fair water to be poured upon the calx two or three several times, and to be at each evaporated, till the calx was very dry, and all the greenish blueness, that is wont to appear in common crystals of silver, was quite carried away. Then I made those I meant to deceive, moisten some part of their skin with their own spittle, and slightly rub the moistened parts with a little of this prepared silver; whereupon they admired to see, that a snow-white body laid upon the white skin should presently produce a deep blackness, as if the stains had been made with ink; especially considering, that this blackness could not, like that produced by ordinary ink, be readily washed off, but required many hours, and part of it some days to its obliteration. And with the same white calx and a little fair water we likewise stained the white shafts of knives, with a lasting black in those parts, where the calx was plentifully enough laid on; for where it was laid on but very thinly, the stain was not quite of so deep a colour.

THE cause of the blackness of those many nations, which by one common name we are wont to call Negroes, has been long since disputed of by learned men, who possibly had not done amiss, if they had also taken into consideration, why some whole races of other animals besides men, as foxes and hares, are distinguished by a blackness not familiar to the generality of animals of the same species. The general opinion (to be mentioned a little lower) has been rejected even by some of the antient geographers, and among the moderns Ortelius and divers other learned men have questioned it. But this is no place to mention what thoughts I have had to and fro about these matters: only as I shall freely acknowledge, that to me the inquiry seems more abstruse than it does to many others, and that because consulting with authors, and with books of voyages, and with travelers, to satisfy myself in matters of fact, I have met with some things among them, which seem not to agree very well with the notions of the most classic authors concerning these things; for it being my present work to deliver rather matters historical than theories, I shall annex some few of my collections, instead of a solemn disputation. It is commonly presumed, that the heat of the climates, wherein they live, is the reason, why so many inhabitants of the scorching regions of Africa are black; and there is this familiar observation to countenance this conjecture, that we plainly see that mowers, reapers, and other country people, who spend the most part of the hot summer days exposed to the sun, have the skin of their hands and faces, which are the parts immediately exposed to the sun and air, made of a darker colour than before, and consequently tending to blackness and contrariwise we observe, that the Danes and some other people that inhabit cold climates, and even the English who feel not so rigorous a cold, have usually whiter faces than the Spaniards, Portugals and other European inhabitants of hotter climates. But this argument I take to be far more specious than convincing; for though the heat of the sun may darken the colour of the skin by that operation, which we in English call sun-burning; yet experience doth not evince, that I remember, that that heat alone can produce a discolouring, that shall amount to a true blackness, like that of Negroes; and we shall see by and by, that even the children of the Negroes not yet ten days old (perhaps not so much by three quarters of that time) will notwithstanding their infancy be of the same hue with their parents. Besides, there is a strong argument to be alleged against the vulgar opinion, that in divers places in Asia under the same parallel, or even of the same degree of latitude with the African regions inhabited by the Blacks, the people are at most but tawny; and in Africa itself divers nations in the empire of Ethiopia are not Negroes, though situated in the torrid zone, and as near the equinoctial, as other nations that are so (as the black inhabitants of Zeylan and Malabar are not in our globes placed so near the line as Amara the famoustest place in Ethiopia). Moreover (that which is of no small moment in our present disquisition) I find not by the best navigators and travellers to the West-Indies, whose books or themselves I have consulted on this subject that excepting perhaps one place or two of small extent, there are any Blacks originally natives of any part of America (for the Blacks now there have been by the Europeans long transplanted thither) though the new world contain in it so great a variety of climates, and particularly reaches quite cross the torrid zone from one tropic to another. And though it be true, that the Danes be a whiter people than the Spaniards, yet that may proceed rather from other causes (not here to be enquired into) than from the coldness of the climate, since not only the Swedes and other inhabitants of those cold countries, are not usually so white as the Danes, nor whiter than other nations in proportion to their vicinity to the pole. [And since the writing of the former part of this essay, having an opportunity on a solemn occasion to take notice of the numerous train of some extraordinary ambassadors sent from the Russian emperor to a great monarch, I observed, that (though it were then winter) the colour of their hair and skin was far less whitish than the Danes who inhabit a milder region is wont to be, but rather from the most part of a darkish brown; and the physician to the ambassador, with whom those Russes came, being asked by me, whether in Muscovy itself the generality of the people were more inclined to have dark-coloured hair than flaxen, he answered affirmatively; but seemed to suspect, that the true and antient Russians, a sect of whom he told me he had met with in one of the provinces of that vast empire, were rather white like the Danes than any thing near so brown as the present Muscovites, whom he guesses to be descended of the Tartars, and to have inherited their colour from them. But to prosecute our former discourse, I shall add for further proof the conjecture I was countenancing, that good authors inform us, that there are Negroes in Africa not far from the Cape of Good Hope, and consequently beyond the southern tropic, and without the torrid zone: much about the same northern latitude (or very little more) wherein there are divers American nations, that are not Negroes, and wherein the inhabitants of Candia, some parts of Sicily and even of Spain, are not so much as Tawny-moors. But (which is a fresh and strong argument against the common opinion) I find by our recent relations of Greenland (our accounts whereof we owe to the curiosity of that royal Virtuoso the present King of Denmark) that the inhabitants are olive-coloured, or rather of a darker hue. But if the case were the same with men, and those other kinds of animals I formerly named, I should offer something as a considerable proof, that cold may do much towards the making men white or black; and however I shall set down the observation as I have met with it, as worthy to come into the history of whiteness and blackness and it is, that in some parts of Russia and of Livonia it is affirmed by Olaus Magnus and others, that hares and foxes (some add partridges) which before were black, or red, or grey, do in the depth of winter become white by reason of the great cold; (for that it should be, as some conceive, by looking upon the snow, seems improbable upon divers accounts): and I remember, that having purposely inquired of a Virtuoso, who lately travelled through Livonia to Mosco, concerning the truth of this tradition, he both told me, he believed it, and added, that he saw divers of those lately named animals either in Russia or Livonia (for I do not very well remember whether of the two) which, though white, when he saw them in winter, they assured him had been black, or other colours, before the winter began, and would be so again when it was over. But for further satisfaction, I also consulted one, that had for some years been an eminent physician in Russia, who though he rejected some other traditions, that are generally enough believed concerning that country, told me nevertheless, that. he saw no cause to doubt of this tradition of Olaus Magnus, as to foxes. and hares; not only because it is a common and uncontrouled assertion of the natives; but also because he himself in the winter could never, that he remembered, see foxes and hares of any other colour than white. And I myself having seen a small white fox, brought out of Russia into England, towards the latter end of winter, foretold those, that shewed him me, that he would change colour in summer; and accordingly coming to look upon him again in July, I found, that the back and sides, together with the upper part of the head and tail, were already grown of a dark colour, the lower part of the head and belly containing as yet a whiteness. Let me add, that were it not for some scruple I have, I should think more than what Olaus relates confirmed by the judicious Olearius, who was twice employed into those parts as a public minister, who in his account of Muscovy has this passage: The hares there are grey; but in some provinces they grow white in the winter. And within some few lines after; It is not very difficult to find the cause of this change, which certainly proceeds only from the outward cold, since I know, that even in summer hares will change colour, if they be kept a competent time in a cellar. I say, were it not for some scruple, because I take notice, that in the same page the author affirms, that the like change of colour, that happens to hares in some provinces of Muscovy, happens to them also in Livonia; and yet immediately subjoins, that in Courland the hares vary not their colour in winter; though these two last named countries be contiguous, that is, severed only by the river of Dugna. For it is scarce conceivable how cold alone should have, in countries so near, so strangely differing an operation, though no less strange a thing is confessed by many, that ascribe the complexion of Negroes to the heat of the sun, when they would have the river of Senega so to bound the Moors, that though on the north-side they are but tawny, on the other side they are black.

THERE is another opinion concerning the complexion of Negroes, that is not only embraced by many of the more vulgar writers, but likewise by that ingenious traveller Mr. Sandys, and by a late most learned critic, besides other men of note; and these would have the blackness of Negroes an effect of Noah's curse ratified by God, upon Cham. But though I think, that even a Naturalist may without disparagement believe all the miracles attested by the Holy Scriptures, yet in this case, to fly to a supernatural cause, will, I fear, look like shifting off the difficulty, instead of resolving it; for we inquire not the first and universal, but the proper, immediate, and physical cause of the jetty colour of Negroes; and not only we do not find expressed in the scripture, that the curse meant by Noah to Cham was the blackness of his posterity, but we do find plainly enough there, that the curse was quite another thing, namely, that he should be a servant of servants, that is, by an Hebraism, a very abject servant to his brethren: which accordingly did in part come to pass, when the Israelites of the posterity of Sem subdued the Canaanites, that descended from Cham, and kept them in great subjection, Nor is it evident, that blackness is a curse; for navigators tell us of black nations who think so much otherwise of their own condition, that they paint the devil white. Nor is blackness inconsistent with beauty, which even to our European eyes consists not so much in colour, as an advantageous stature, a comely symmetry of the parts of the body, and good features in the face. so that I see not, why blackness should be thought such a curse to the Negroes, unless perhaps it be, that being wont to go naked in those hot climates, the colour of their skin does probably, according to the doctrine above delivered, make the sun-beams more scorching, to them, than they would prove to a people of a white complexion.

GREATER probability there is, that the principal cause (for I would not exclude all concurrent ones) of the blackness of Negroes is some peculiar and seminal imperfection: for not only we see, that Blackmoor boys, brought over into these colder climates, lose not their colour; but good authors inform us, that the offspring of Negroes transplanted out of Africa, above a hundred years ago, retain still the complexion of their progenitors, though possibly in tract of time it will decay; as, on the other side, the white people removing into very hot climates, have their skins by the heat of the sun scorched into dark colours; yet neither they, nor their children have been observed, even in the countries of negroes, to descend to a colour amounting to that of the natives. Whereas I remember I have read in Piso's excellent account of Brasil, that betwixt the Americans and Negroes are generated a distinct sort of men, which they call Cabocles; and betwixt Portugals and Æthiopian women, he tells us, he has sometimes seen twins, whereof one had a white skin, the other a black: not to mention here some other instances he gives, that the productions of the mixtures of differing people, that is (indeed) the effects of seminal impressions, which they consequently argue to have been their causes. And we shall not much scruple at this, if we confider, that even organical parts may receive great differences from such peculiar impressions, upon what account soever they came to be settled in the first individual persons, from whom they are propagated to posterity, as we see in the blobber-lips and flat-noses of most nations of negroes. And if we may credit what learned men deliver concerning the little feet of the Chineses, the Macrocephali taken notice of by Hippocrates will not be the only instance we might apply to our present purpose. And on this occasion it will not perchance be impertinent to add something of what I have observed in other animals, as there are a sort of hens, that want rumps; and that (not to mention, that in several places there is a sort of crows or daws, that are not coal black as ours, but partly of a whitish colour) in spight of Pophyry's examples of inseparable accidents, I have seen a perfectly white raven, as to bill as well as feathers, which I attentively considered, for fear of being imposed upon. And this recalls into my memory, what a very ingenious physician has divers times related to me of a young lady, to whom being called, he found, that though she much complained of want of health, yet there appeared so little cause either in her body, or her condition, to guess, that she did any more than fancy herself sick; that scrupling to give her physic, he persuaded her friends rather to divert her mind by little journeys of pleasure: in one of which going to visit St. Winifred's well, this lady, who was a catholic, and devout in her religion, and a pretty while in the water to perform some devotions, and had occasion to fix her eyes very attentively upon the red pebble stones, which in a scattered order made up a good part of those that appeared through the water; and a while after growing big, she was delivered of a child, whose white skin was copiously speckled with spots of the colour and bigness of those stones; and though now this child have already lived several years, yet she still retains them. I have but two things to add concerning the blackness of Negroes; the one is, that the seat of that colour seems to be but the thin epidermis, or outward skin; for I knew a young Negro, who having been lightly sick of the small-pox or measles (for it was doubted, which of the two was his disease) I found by inquiry of a person, that was concerned for him, that in those places the little turnours had broke their passage through the skin, when they were gone, they left whitish specks behind them; and the lately commended Piso assures us, that having the opportunity in Brasil to dissect many Negroes, he clearly found, that their blackness went no deeper than the very outward skin, which cuticula or epidermis being removed, the undermost skin or cutis appeared just as white as that of European bodies. And the like has been affirmed to me by a physician of our own, whom hearing he had dissected a Negroe here in England, I consulted about this particular. The other thing to be here taken notice of concerning Negroes is, that having inquired of an intelligent acquaintance of mine (who keeps in the Indies about three hundred of them, as well women as men, to work in his plantations) whether their children come black into the world; he answered, that they did not, but were brought forth of almost the like reddish colour with our European children: and having further, enquired, how long it was before these infants appeared black, he replied, that it was not wont to be many days. And agreeable to this account I find that given us in a freshly published French book, written by a Jesuit, that had good opportunity of knowing the truth of what he delivers; for being, one of the missionaries of his order into the southern America upon the laudable design of converting infidels to Christianity, he baptized several infants, which when newly born were much of the same colour with European babes, but within about a week began to appear of the hue of their parents. But more pregnant is the testimony of our countryman Andrew Battel, who being sent prisoner by the Portugals to Angola, lived there, and in the adjoining regions, partly as a prisoner, partly as a pilot, and partly as a soldier, near eighteen years; and he mentioning the African kingdom of Longo, peopled with Blacks, has this passage: The children in this country are born white, and change their colour in two days to a perfect black. As for example, The Portugals, which dwell in the kingdom of Longo, have sometimes children by the Negroe-women; and many times the fathers are deceived, thinking, when the child is born, that it is theirs and within two days it proves to be the son or daughter of a Negroe, which the Portagals greatly grieve at. And the same person has elsewhere a relation, which, if he have made no use at all of the liberty of a traveller, is very well worth our notice since this, together with that we have formerly mentioned of seminal impressions, shews a possibility, that a race of Negroes might be begun, though none of the sons of Adam for many precedent generations were of that complexion. For I see not, why it should not be at least as possible, that white parents may sometirnes have black children, as that African Negroes should sometimes have lastingly white ones; especially since concurrent causes may easily more befriend the unions of the former kind, than under the scorching heat of Africa those of the latter. And I remember on the occasion of what he delivers, that of the white raven formerly mentioned, the possessor affirmed to me, that in the nest, out of which he was taken white, they found with him but one other young one, and that he was of as jetty a black as any common raven. But let us hear our author himself: Here are (says he, speaking of the formerly mentioned regions) born in this country white children, which is very rare among them, for their parents are Negroes; and when any of them are born, they are presented to the king, and are called Dondos; these are as white as any white men. These are the king's witches, and are brought up in witchcraft, and always wait on the king: there is no man, that dares meddle with these Dondos; if they go to the market, they may take what they list, for all men stand in awe of them. The king of Longo hath four of them. And yet this country in our globes is placed almost in the midst of the torrid zone (four or five degrees southward of the line.) And our author elsewhere tells us of the inhabitants, that they are so fond of their blackness, that they will not suffer any, that is not of that colour (as the Portugals that come to trade thither) to be so much as buried in their land; of which he annexes a particular example, that may be seen in his voyage preserved by our industrious countryman Mr. Purchas. But it is high time for me to dismiss observations, and so on with experiments

THE way, Pyrophilus, of producing whiteness by chymical precipitations is very well worth our observing; for thereby bodies, of very differing colours; as well as natures, though dissolved in several liquors, are all brought into calces or powders that are white. Thus we find that not only crabs-eyes, that are of themselves white, and pearls that are almost so, but coral and minium that are red, being dissolved in spirit of vinegar, may be uniformly precipitated by oil of tartar into white powders. Thus silver and tin separately dissolved in aqua fortis will the one precipitate itself, and the other be precipitated by common salt-water into a white calx, and so will crude lead and quicksilver first dissolved likewise in aqua fortis. The like calx will be afforded, as I have tried, by a solution of that shining mineral tinglass dissolved in aqua fortis, and precipitated out of it; and divers of these calces may be made at least as fair and white, if not better coloured, if instead of oil of tartar they were precipitated with oil of vitriol, or with another liquor I could name. Nay, that black mineral antimony itself, being reduced by and with the salts, that concur to the composition of common sublimate, into that clear though unctuous liquor, that chymists commonly call rectified butter of antimony, will, by the bare affusion of store of fair water, be struck down into that snow-white powder, which when the adhering saltness is well washed off, chymists are pleased to call Mercurius Vitæ; though the like powder may be made of antimony, without the addition of any mercury at all. And this lactescence, if I may so call it, does also commonly ensue, when spirit of wine, being impregnated with those parts of gums or other vegetable concretions, that are supposed to abound with sulphureous corpuscles, fair water is suddenly poured upon the tincture or solution. And I remember, that very lately I did, for trial sake, on a tincture of Benjamin drawn with spirit of wine, and brought to be as red as blood, pour some fair water; which presently mingling with the liquor, immediately turned the whole mixture white. But if such seeming milks be suffered to stand unstirred for a convenient while, they are wont to let fall to the bottom a resinous substance, which the spirit of wine diluted and weakened by the water poured into it is unable to support any longer. And something of kin to this change of colour in vegetables is that, which chymists are wont to observe upon the pouring of acid spirits upon the red solution of sulphur, dissolved in an infusion of pot-ashes, or in some other sharp lixivium; the precipitated sulphur, before it subsides, immediately turning the red liquor into a white one. And other examples might be added of this way of producing whiteness in bodies by precipitating them out of the liquors, wherein they have been dissolved. But I think it may be more useful to admonish you, Pyrophilus, that this observation admits of restrictions, and is not so universal, as by this time perhaps you have begun to think it: for though most precipitated bodies are white, yet I know sorne that are not; for gold dissolved in aqua regis, whether you precipitate it with oil of tartar, or with spirit of sal armoniac, will not afford a white, but a yellow calx. Mercury also, though reduced into sublimate, and precipitated with liquors abounding with volatile salts, as the spirits drawn from urine, hartshorn, and other animal substances, yet will afford, as we noted in our first experiment about whiteness and blackness, a white precipitate ; yet with the solution of pot-ashes and other lixiviate salts, it will let fall an orange-tawny powder. And so will crude antimony, it being dissolved in a strong lye, if you pour (as far as I remember) any acid liquor upon the solution newly filtrated, whilst it is yet warm. And if upon the filtrated solution of vitriol, you pour a solution of one of these fixed salts, there will subside a copious substance, very far from having any whiteness, which the chymists are pleased to call (how properly I have elsewhere examined) the sulphur of vitriol. So that most dissolved bodies being by precipitation brought to white powders, and yet some affording precipitates of other colours, the reason of both the phænomena may deserve to be enquired into.

Some learned modern writers are of opinion, that the account, upon which whiteness and blackness ought to be called, as they commonly are, the two extreme colours, is, that blackness (by which I presume is meant the bodies endowed with it) receives no other colours; but whiteness very easily receives them all: whence some of them compare whiteness to the Aristotelian Materia prima, that being capable of any sort of forms, as they suppose white bodies to be of every kind of colour. But not to dispute about names or expressions, the thing itself that is affirmed as matter of fact, seems to be true enough in most cases, not in all, or so as to hold universally. For though it be a common observation among dyers, that cloaths, which, have once been thoroughly imbued with black, cannot so well afterwards be dyed into lighter colours, the pre-existent dark colour infecting the ingredients, that carry the ligthter colour to be introduced, and making it degenerate into some more sad one; yet the experiments lately mentioned may shew us, that where the change of colour in black bodies is attempted, not by mingling bodies of lighter colours with them, but by addition of such things as are proper to alter the texture of those corpuscles that contain the black colour, it is no such difficult matter, as the lately mentioned learned men imagine, to alter the colour of black bodies. For we saw, that inks of several kinds might in a trice be deprived of all their blackness; and those made with logwood and red-roses might all be changed, the one into a red, the other into a reddish liquor; and with oil of vitriol I have sometimes turned black pieces of silk into a kind of yellow, and though the taffaty were thereby made rotten, yet the spoiling of that does no way prejudice the experiment, the change of black silk into yellow being nevertheless true, because the yellow silk is the less good. And as for whiteness think the general affirmation of its being so easily destroyed, or transmuted by any other colour, ought not to be received without some cautions and restrictions. For whereas, according to what I formerly noted, lead is by calcination turned into that red powder we call minium, and tin by calcination reduced to a white calx; the common putty, that is sold and used so much in shops, instead of being, as it is pretended and ought to be, only the calx of tin; is, by the artificers that make it, to save the charge of tin, made (as some of themselves have confessed, and as I long suspected by the cheap rate it may be bought for) but of half tin and half lead, if not far more lead than tin; and yet the putty, in spite of so much lead, is a very white powder, without disclosing any mixture of minium. And so if you take two parts of copper, which is a high coloured metal, to but one of tin, you may by fusion bring them into one mass, wherein the whiteness of the tin is much more conspicuous and predominant than the reddishness of the copper. And on this occasion it may not be impertinent to mention an experiment, which I relate upon the credit of a very honest man, whom I purposely inquired of about it, being myself not very fond of making trials with arsenic: the experiment is this; that if you colliquate arsenic: and copper in a due proportion, the arsenic will blanch the copper both within and without, which is an experiment well enough known. But when I inquired, whether or no this white mixture being skilfully kept a while upon the cupel would not let go its arsenic, which made whiteness its predominant colour, and return to the reddishness of copper, I was assured of the affirmative. so that among mineral bodies, some of those that are white, may be far more capable, than those I am reasoning with seem to have known, of eclipsing others, and of making their colour predominant in mixtures. In further confirmation of which may be added, that I remember, that I also took a lump of silver and gold melted together, wherein, by the estimate of a very experienced refiner, there might be about a fourth or third part of goId; and yet the yellow colour of the gold was so hid by the white of the silver that the whole mass appeared to be but silver; and when it was rubbed upon the touch-stone, an ordinary beholder could scarce have distinguished it from the touch of common silver; though if I put a little aqua fortis upon any part of the white surface it had given the touch-stone, the silver in the moistened part being immediately taken up and concealed by the liquor, the golden particles would presently disclose that native yellow, and look rather as if gold, than if the above-mentioned mixture had been rubbed upon the stone.

I TOOK a piece of black horn (polished as being part of a comb) this with a piece of broken glass I scraped into many thin and curled flakes, some shorter and some longer; and having laid a pretty quantity of these scrapings together, I found, as I looked for, that the heap they composed was white; and though, if I laid it upon a clean piece of white-paper, its colour seemed somewhat eclipsed by the greater whiteness of the body it was compared with, looking somewhat like linen, that had been sullied by a little wearing; yet if I laid it upon a very black body, as upon a beaver hat, it then appeared to be of a good white. Which experiment that you may in a trice make when you please, seems very much to disfavour both their doctrine, that would have colours to flow from the substantial forms of bodies; and that of the chymists also, who ascribe them to one or other of their three hypostatical principles: for though in our case there was so great a change made that the same body, without being substantially either increased or lessened, passes immediately from one extreme colour to another (and that too from black to white) yet this so great and sudden change is effected by a slight mechanical transposition of parts, there being no salt or sulphur or mercury, that can be pretended to be added or taken away, nor yet any substantial form, that can reasonably be supposed to be generated and destroyed, the effect proceeding only from a local motion of the parts, which so varied their position, as to multiply their distinct surfaces, and to qualify them to reflect far more light to the eye, than they could before they were scraped off from the entire piece of black horn.

AND now, Pyrophilus, it will not be improper for us to take some notice of an opinion touching the cause of blackness, which I judged it not so unreasonable to question, till I had set down some of the experiments, that might justify my disent from it. You know, that of late divers learned men, having adopted the three hypostatical principles, besides other notions of the chymists, are very inclinable to reduce all qualities of bodies to one or other of those three principles; and particularly assign for the cause of blackness the sooty steam of adust or torrified sulphur. But I hope, that what we have delivered above to countenance the opinion we have proposed about the cause of blackness, will so easily supply you with several particulars, that may be made use of against this opinion, that I shall now represent to you but two things concerning it.

AND first, it seems, that the favourers of the chymical theories might have pitched upon some more proper term, to express the efficient of blackness than sulphur adust; for we know, that common sulphur, not only when melted, but even when sublime. does not grow black by suffering the action of the fire, but continues and ascends yellow, and rather more than less white, than it was before its being exposed to the fire. And if it be set on fire, as when we make that acid liquor, that chymists call Okum Sulphuris per campanam, it affords very little soot: and indeed the flame yields so little, that it will scarce in any degree black a sheet of white paper, held a pretty while over the flame and smoke of it, which is observed rather to whiten than infect linen, and which does plainly make red roses grow very pale, but not at all black, as far as the smoke is permitted to reach the leaves. And I can shew you a sort of fixt sulphur made by an industrious laborant of your acquaintance, who assured me, that he was wont to keep it for divers weeks together night and day in a naked and violent fire, almost like that of the glass-house; and when, to satisfy my curiosity, I made him take out a lump of it, though it were glowing hot (and yet not melted) it did not, when I had suffered it to cool, appear black, the true colour of it being a true red. I know it may be said, that chymists, in the opinion above recited mean the principle of sulphur, and not common sulphur, which receives its name, not from its being all perfectly of a sulphurcous nature, but for that plenty and predominancy of the sulphureous principle in it. But allowing this, it is easy to reply, that according to this very reason, torrified sulphur should afford more blackness than most other concretes, wherein that principle is confessed to be far less copious. Also when I have exposed camphire to the fire in close vessels, as inflammable, and consequently (according to the chymists) as sulphureous a body as it is, I could not by such a degree of heat as brought it to fusion, and made it to boil in the glass, impress any thing of blackness, or of any other colour, than its own pure white, upon this vegetable concrete. But what shall we say to spirit of wine, which being made by a chymical analysis of the liquor that affords it, and being totally inflammable, seems to have a full right to the title they give it of Sulphur Vegetabile ? and yet this fluid sulphur not only contracts not any degree of blackness by being often so heated, as to be made to boil, but when it burns away with an actual flame, I have not found, that it would discolour a piece of white paper held over it, with any discernable soot. Tin also, that wants not, according to the chymists, a Sulphur Joviale, when thoroughly burned by the fire into a calx, is not black, but eminently white. And I lately noted to you out of Bellonius, that the charcoals of oxy-cedar are not of the former of these two colours, but of the latter. And the smoke of our Tinby coals here in England has been usually observed rather to blanch linen than to black it. To all which other particulars of the like nature might be added; but I rather chuse to put you in mind of the third experiment, about making black liquors, or ink, of bodies, that were none of them black before. For how can it be said, that when those liquors are put together actually cold, and continue so after their mixture, there intervenes any new adustion of sulphur to produce the emergent blackness? (and the same question will be applicable to the blackness produced upon the blade of a knife, that has cut lemons and some kind of sour apples, if the juice, though both actually and potentially cold, be not quickly wiped off.) And when by the instilling either of a few drops of oil of vitriol, as in the second experiment, or of a little of the liquor mentioned in the passage pointed at in the fourth experiment (where I teach at once to destroy one black ink, and make another) the blackness produced by those experiments is presently destroyed; if the colour proceeded only from the plenty of sulphureous parts, torrified in the black bodies, I demand what becomes of them, when the colour so suddenly disappears? For it cannot reasonably be said, that all those, that sufficed to make so great a quantity of black matter, should resort to so very small a proportion of the clarifying liquor (if I may so call it) as to be diluted by it, without at all denigrating it. And if it be said, that the instilled liquor dispersed those black corpuscles, I demand, how that dispersion comes to destroy their blackness, but by making such a local motion of their parts, as destroys their former texture? Which may be a matter of such moment in cases like ours, that I remember, that I have in few hours, without addition, from soot itself, attained pretty store of crystalline salt, and good store of transparent liquor; and (which I have on another occasion noted as remarkable) this so black substance had its colour so altered, by the change of texture it received from the fire, wherewith it was distilled, that it did for a great while afford such plenty of very white exhalations, that the receiver, though large, seemed to be almost filled with milk.

SECONDLY, But were it granted, as it is in some cases not improbable, that divers bodies may receive a blackness from a sooty exhalation, occasioned by the adustion of their sulphur, which (for the reasons lately mentioned) I should rather call their oily parts; yet still this account is applicable but to some particular bodies, and will afford us no general theory of blackness. For if, for example, white hartshorn being, in vessels well suited to each other, exposed to the fire, be said to turn black by the infection of its own smoke, I think I may justly demand, what it is that makes the smoke or soot itself black, since no such colour, but its contrary, appeared before in the hartshorn? And with the same reason, when we are told, that torrified sulphur makes bodies black, I desire to be told also, why torrefaction makes sulphur itself black? Nor will there be any satisfactory reason assigned of these queries, without taking in those fertile as well as intelligible mechanical principles of the position and texture of the minute parts of the body in reference to the light and the eye, and these applicable principles may serve the turn in many cases, where the adustion of sulphur cannot be pretended; as in the appearing blackness of an open window looked upon at a somewhat remote distance from the house; as also in the blackness men think they see in the holes, that happen to be in white linen, or paper of the like colour; and in the increasing blackness immediately produced barely by so rubbing velvet, whose piles were inclined before, as to reduce them to a more erect posture; in which and in many other cases formerly alleged, there appears nothing requisite to the production of the blackness, but the hindering of the incident beams of light from rebounding plentifully enough to the eye. To be short, those I reason with, do concerning blackness what the chymists are wont also to do concerning other qualities; namely, to content themselves to tell us, in what ingredient of a mixt body, the quality enquired after does reside, instead of explicating the nature of it, which (to borrow a comparison from their own laboratories) is much as if in an inquiry after the cause of salivation, they should think it enough to tell us, that the several kinds of precipitates of gold and mercury, as likewise of quicksilver and siIver (for I know the make and use of such precipitates also) do salivate upon the account of the mercury, which though disguised abounds in them; whereas the difficulty is as much to know upon what account mercury itself, rather than other bodies, has that power of working by salivation. Which I say not, as though it were, not something (and too often the most we can arrive at) to discover in which of the ingredients of a compounded body the quality, whose nature is sought, resides; but because, though this discovery itself may pass for something, and is oftentimes more than what is taught us about the same subjects in the schools, yet we ought not to, think it enough, when more clear and particular accounts are to be had.

The Experimental History of C O L O U R S begun.

P A R T I I I

BECAUSE that, according to the conjectures I have above proposed, one of the most general causes of the diversity of colours in opacous bodies, is, that some reflect the light mingled with more, others with less of shade (either as to quantity, or as to interruption;) I hold it not unfit to mention, in the first place, the experiments, that I thought upon to examine this conjecture. And though coming to transcribe them out of some physiological Adversaria I had written in loose papers, I cannot find one of the chief records I had of my trials of this nature, yet the papers, that escaped miscarrying, will, I presume, suffice to manifest the main thing, for which I now allege them. I find then among my Adversaria the following narrative.

October the 11th, About ten in the morning in sun-shiny weather (but not without fleeting clouds) we took several sorts of paper stained, some of one colour, and some of another; and in a darkened room, whose window looked southward, we cast the beams, that came in at a hole about three inches and a half in diameter, upon a white wall, that was placed on one side, about five foot distance from them.

THE white gave much the brightest reflection.

THE green, red, and blue being compared together, the red gave much the strongest reflection, and manifestly enough also, threw its colour upon the wall: the green and, blue were scarce discernable by their colours, and seemed to reflect an almost equal light.

THE yellow, compared with the two last named, reflected somewhat more light.

THE red and purple being compared together, the former manifestly reflected a good deal more light.

THE blue and purple compared together, the former seemed to reflect a little more light, though the purple colour were more manifestly seen.

A SHEET of very well sleeked marbled paper being applied as the others, did not cast any of its distinct colours upon the wall, nor throw its light upon it with an equal diffusion; but threw the beams unstained and bright to this and that part of the wall, as if its polish had given it the nature of a specular body. But comparing it with a sheet of white paper, we found the reflection of the latter to be much stronger, it diffusing, almost as much light to a good extent as the marble paper did to one part of the wall.

THE green and purple left us somewhat in suspense, which released the most light; only the purple seemed to have some little advantage over the green, which was dark in its kind.

THUS much I find in our above-mentioned collections; among which there are also some notes concerning the production of compounded colours, by reflection from bodies differingly coloured. And these notes we intended should supply us with what we should mention as our second experiment: but having lost the paper, that contained the particulars, and remembering only in general, that if the objects, which reflected the light, were not strongly coloured and somewhat glossy, the reflected beams would not manifestly make a compounded colour upon the wall, and even then but very faintly; we shall now say no more of that matter, only reserving ourselves to mention hereafter the composition of a green, which we still retain in memory

WE may add, Pyrophilus, on this occasion, that though a darkened room be generally thought requisite to make the colour of a body appear by reflection from another body, that is not one of those, that are commonly agreed upon to be specular (as polished metal, quicksilver, glass, water, &c.) yet I have often observed, that when I wore doublets lined with some silken stuff, that was very glossy and vividly coloured, especially red, I could in an enlightened room plainly enough discern the colour upon the pure white linen, that came out at my sleeve, and reached to my cuffs; as if that fine white body were more specular than coloured and unpolished bodies are thought capable of being.

WHILST we were making the newly mentioned experiments, we thought fit to try also what composition of colours might be made by altering the light in its passage to the eye, by the interposition not of perfectly diaphanous bodies (that having been already tried by others as well as by us, as we shall soon have occasion to take notice) but of semi-opacous bodies, and those such as looked upon in an ordinary light, and not held betwixt it and the eye, are not wont to be discriminated from the rest of opacous bodies. Of this trial our mentioned Adversaria present us the following account:

HOLDING these sheets, sometimes one, sometimes the other of them, before the hole betwixt the sun and the eye, with the coloured sides obverted to the sun; we found them single to be somewhat transparent, and appear of the same colour as before, only a little altered by the great light they were placed in: but laying two of them one over another, and applying them so to the hole, the colours were compounded as follows.

THE blue and yellow scarce exhibited any thing but a darker yellow, which we ascribed to the coarseness of the blue paper, and its darkness in its kind. For applying the blue parts of the marbled paper with the yellow paper after the same manner, they exhibited a good green.

THE yellow and red looked upon together gave us but a dark red, somewhat (and but a little) inclining to an orange colour.

THE purple and red looked on together appeared more scarlet.

THE purple and yellow made an orange.

THE green and red made a dark orange-tawny.

THE green and purple made the purple appear more dirty.

THE blue and purple made the purple more lovely, and far more deep.

THE red parts of the marbled paper, looked upon with the yellow, appeared of a red far more like scarlet than without it.

BUT the fineness or coarseness of the papers, their being carefully or slightly coloured, and divers other circumstances, may so vary the events of such experiments as these, that if, Pyrophilus, you would build much on them, you must carefully repeat them.

THE triangular prismatical glass being the instrument, upon whose effects we may the most commodiously speculate the nature of emphatical colours (and perhaps that of others too;) we thought it might be useful to observe the several reflections and refractions, which the incident beams of light suffer in rebounding from it, and passing through it. And this we thought might be best done, not (as is usual) in an ordinary enlightened room, where (by reason of the difficulty of doing otherwise) even the curious have left particulars unheeded, which may in a convenient place be easily taken notice of; but in a darkened room, where by placing the glass in a convenient posture, the various reflections and refractions may be distinctly observed, and where it may appear, what beams are untinged, and which they are, that, upon the bodies, that terminate them, do paint either the primary or secondary iris. In pursuance of this we did, in the above-mentioned darkened room, make observation of no less than four reflections, and three refractions, that were afforded us by the same prism; and thought, that, notwithstanding what was taught us by the rules of catoptricks and dioptricks, it would not be amiss to find also, by hiding sometimes one part of the prism, and sometimes another, and observing where the light or colour vanished thereupon, by which reflection and by which refraction each of the several places whereon the light rebounding from, or passing through, the prism, appeared either sincere or tincted, was produced. But because it would be tedious, and not so intelligible to deliver this in words, I have thought fit to refer you to the annexed scheme, where the newly mentioned particulars may be at one view taken notice of.

Click here for larger image

I KNOW not whether you will think it inconsiderable to annex to this experiment, that we observed in a room not darkened, that the prismatical iris (if I may so call it) might be reflected without losing any of its several colours (for we now consider not their order) not only from a plain looking-glass and from the calm surface of fair water, but also from a concave looking-glass and that refraction did as little destroy those colours as reflection. For by the help of a large (double convex) burning-glass, through which we refracted the sun-beams, we found, that one part of the iris might be made to appear either beyond, or on this side of the other parts of the same iris; but yet the same vivid colours would appear in the displaced part (if I may so term it) as in the other. To which I shall add, that having, by hiding the side of the prism, obverted to the sun with an opacous body, wherein only one small hole was left for the light to pass though, reduced the prismatical iris (cast upon white paper) into a very narrow compass, and looked upon it through a microscope the colours appeared the same as to kind, that they did to the naked eye.

IT may afford matter of speculation to the inquisitive, such as you, Pyrophilus, that as the colours of outward objects brought into a darkened room do so much depend for their visibility upon the dimness of the light they are there held by, that the ordinary light of the day being freely let in upon them, they immediately disappear; So our trials have informed us, that as to the prismatical iris painted on the floor by the beams of the sun trajected thorough a triangular glass, though the colours of it appear very vivid even at noon-day, and in sun-shiny weather, yet by a more powerful light they may be made to disappear. For having sometimes, (in prosecution of some conjectures of mine not now to be insisted on) taken a large metalline concave speculum, and with it cast the converging beams of the sun upon a prismatical iris, which I had caused to be projected upon the floor, I found, that the over-powerful light made the colours of the iris disappear. And if I so reflected the light, as that it crossed but the middle of the iris, in that part only the colours vanished or were made invisible; those parts of the iris, that were on the right and left hand of the reflected light (which seemed to divide them, and cut the iris asunder) continuing to exhibit the same colours as before. But upon this we must not now stay to speculate.

I HAVE sometimes thought it worth while to take notice, whether or no the colours of opacous bodies might not appear to the eye somewhat diversified, not only by the disposition of the superficial parts of the bodies themselves, and by the postion of the eye in reference to the object and the light, (for these things are notorious enough) but according also to the nature of the lucid body, that shines upon them. And I remember, that in prosecution of this curiosity, I observed a manifest difference in some kinds of coloured bodies looked on by day-light, and afterwards by the light of the moon, either directly falling on them, or reflected upon them from a concave looking-glass. But not finding at present, in my collections about colours, any thing set down of this kind, I shall, till I have opportunity to repeat them, content myself to add what I find registered concerning colours looked on by candlelight, in regard that not only the experiment is more easy to be repeated, but the objects being the same sorts of coloured paper lastly mentioned, the collation of the two experiments may help to make the conjectures they will suggest somewhat the less uncertain.

WITHIN a few days of the time above-mentioned, divers sheets of coloured paper, that had been looked upon before in the sun-shine, were looked upon at night by the light of a pretty big, candle (snuffed) and the changes that were observed were these:

THE yellow seemed much fainter than in the day, and inclinable to a pale straw-colour.

THE red seemed little changed; but seemed to reflect light more strongly than any other colour (for white was none of them).

A FAIR deep green looked upon by itself, seemed to be a dark blue: but being looked upon together with a dark blue, appeared greenish; and beheld together with a yellow, appeared more blue than at first.

THE blue looked more like a deep purple or murray, than it had done in the daylight.

THE purple seemed very little altered.

THE red looked upon with the yellow made the yellow look almost like brown cap-paper.

N.B. THE caution subjoined to the third experiment is also applicable to this.

BUT here I must not omit to subjoin, that to satisfy ourselves, whether or no the light of a candle were not made unsincere, and as it were tinged with a yellow colour, by the admixtion of the corpuscles it assumes from its fuel; we (did not content ourselves with what appears to the naked eye, but taking a pretty thick rod or cylinder (for thin pieces would not serve the turn) of deep blue glass, and looking upon the candle's flame at a convenient distance through it, we perceived, as we expected, the flame to look green: which, as we often note, is the colour wont to emerge from the composition of opacous bodies, which were apart one of them blue, and the other yellow. And this perchance may be the main reason of that, which some observe, that a sheet of very white paper being looked upon by candle-light, it is not easy at first to discern it from a light yellow or lemon colour; white bodies (as we have elsewhere observed) having more than those, that are otherwise coloured, of a specular nature, in regard that though they exhibit not (unless they be polished) the shape of the luminary, that shines on them, yet they reflect its light more sincere and untroubled, by either shades or refractions, than bodies of other colours, (as blue, or green, or yellow, or the like.)

WE took a leaf of such foliated gold, as apothecaries are wont to gild their pills with; and with the edge of a knife, (lightly moistened by drawing it over the surface of the tongue, and afterwards) laid upon the edge of the gold leaf, we so fastened it to the knife, that being held against the light, it continued extended like a little flag. This leaf being held very near the eye, and obverted to the light, appeared so full of pores, that it seemed to me such a kind of transparency, as that of a sieve, or a piece of cypress, or a love-hood; but the light that passed by these pores was in its passages so tempered with shadow, and modified, that the eye discerned no more a golden colour, but a greenish blue. And for others satisfaction, we did in the night look upon a candle through such a leaf of gold; and by trying the effects of several proportions of distance betwixt the leaf, the eye and the light, we quickly hit upon such a position for the leaf of gold, as that the flame looked on through it, appeared of a greenish blue, as we have seen in the day-time. The like experiment tried with a leaf of silver succeeded not well.

WE have sometimes found in the shops of our druggists a certain wood, which is there called Lignum Nephriticum, because the inhabitants of the country, where it grows, are wont to use the infusion of it made in fair water against the stone of the kidneys. And indeed an eminent physician of our acquaintance, who has very particularly inquired into that disease, affures me, that he has found such an infusion one of the most effectual remedies, which he has ever tried against that formidable disease. The ancientest account I have met with of this simple, is given us by the experienced Monardes in these words: Nobis, says he, Nova Hispana mittet quoddam ligni genus crassum & enode, cujus usus jam diu receptus fuit in his regionibus ad renum vitia, & urinæ difficultates ac arenulas pellendas. Fit autem hac ratione; lignum assulatim & minutim concisum in limpidissima aqua fontana maceratur, inque ea relinquitur, donec aqua à bibentibus absumpta sit; dimidia hora post injectum lignum aqua cœruleum colorem contrahit, qui sensin; intenditur pro temporis diuturnitate, tametsi, lignum candidum fit. This wood, Pyrophilus, may afford us an experiment, which, besides the singularity of it, may give no small assistance to an attentive considerer towards the detection of the nature of colours. The experiment, as we made it is this: Take Lignum Nephriticum, and with a knife cut it into thin slices; put about a handful of these slices into two, three or four pounds of the purest spring-water; let them infuse there a night; but if you be in haste, a much shorter time may suffice. Decant this impregnated water into a clear glass phial; and if you hold it diredly between the light and your eye, you shall see it wholly tincted, (excepting the very top of the liquor, wherein you will sometimes discern a sky-coloured circle) with an almost golden colour, unless your infusion have been made too strong of the wood; for in that case it will against the light appear somewhat dark and reddish, and requires to be diluted by the addition of a convenient quantity of water. But if you hold this phial from the light, so that your eye be placed betwixt the window and the phial, the liquor will appear of a deep and lovely ceruleous colour, of which also the drops, if any be lying or, the outside of the glass, will seem to be very perfectly. And thus far we have tried the experiment, and found it to succeed even by the light of candles of the larger size. If you so hold the phial over against your eyes, that it may have a window on one side of it, and a dark part of the room both before it and on the other side, you shall see the liquor partly of a bluish and partly of a golden colour. If turning your back to the window, you pour out some of the liquor towards the light and towards your eyes, it will seem at the coming out of the glass to be perfectly ceruleous; but when it is fallen down a little way, the drops may seem parti-coloured, according as the beams of light do more or less fully penetrate and illuminate them. If you take a bason about half full of water, and having placed it so in the sun-beams shining into a room, that one part of the water may be freely illustrated by the beams of light, and the other part of it darkened by the shadow of the brim of the bason; if then, I say, you drop of our tincture, made somewhat strong, both into the shade and illuminated parts of the water, you may by looking upon it from several places, and by a little agitation of the water, observe divers pleasing phænomena, which were tedious to particularize, If you pour a little of this tincture upon a sheet of white paper, so as the liquor may remain of some depth upon it, you may perceive the neighbouring drops to be partly of one colour, and partly of the other, according to the position of your eye in reference to the light when it looks upon them; but if you pour off the liquor, the paper will seem dyed of an almost yellow colour. And if a sheet of paper with some of this liquor in it be placed in a window where the sun-beams may shine freely on it, then if you turn your back to the sun and take a pen or some such slender body, and hold it over-thwart betwixt the sun and the liquor, you may perceive, that the shadow projected by the pen upon the liquor will not all of it be a vulgar and dark, but in part a curiously coloured shadow; that edge of it, which is next the body that makes it, being almost of a lively golden colour, and the remoter verge of a ceruleous one.

THESE and other phænomena, which I have observed in this delightful experiment, divers of my friends have looked upon not without some wonder; and I remember an excellent oculist, finding by accident in a friend's chamber a fine phial full of this liquor, which I had given that friend and having never heard any thing of the experiment, nor having any body near him, that could tell him what this strange liquor might be, was a great while apprehensive, as he presently after told rne, that some strange new distemper was invading his eyes. And I confess, that the unusualness of the phænomena made me very solicitous to find out the cause of this experiment; and though I am far from pretending to have found it, yet my inquiries have, I suppose, enabled me to give such hints, as may lead your greater sagacity to the discovery of the cause of this wonder. And first finding that this tincture, if it were too copious in the water, kept the colours from being so lively, and their change from being so discernible, and finding also that the impregnating virtue of this wood did by its being frequently infused in new water by degrees decay; I conjectured that the tincture afforded by the wood must proceed from some subtiler parts of it drawn forth by the water, which swimming to and fro in it, did so modify the light, as to exhibit such and such colours: and because these subtile parts were so easily solube even in cold water, I concluded that they must abound with salts, and perhaps contain much of the essential salt, as the chymists call it, of the wood. And to try whether these subtile parts were volatile enough to be distilled, without the dissolution of their texture, I carefully distilled some of the tincted liquor in very low vessels, and the gentle heat of a lamp furnace; but found all that came over to be as limpid and colourless as rock-water, and the liquor remaining in the vessel to be so deeply ceruleous, that it required to be opposed to a very strong light to appear of any other colour. I took likewise a phial with spirit of wine, and a little salt of hartshorn, and found that there was a certain proportion to be met with betwixt the liquor and the salt, which made the mixture fit to exhibit some little variety of colours not observable in ordinary liquors, as it was variously directed in reference to the light and the eye; but this change of colour was very far short from that which we had admired in our tincture. But, however, I suspected that the tinging particles did abound with such salts, whose texture, and the colour springing from it, would probably be altered by piercing acid salts, which would in likelihood either make some dissipation of their parts, or associate themselves to the like bodies, and either way alter the colour exhibited by them; whereupon pouring into a small phial, full of impregnated water, a very little spirit of vinegar, I found that, according to my expectation, the ceruleous colour immediately vanished, but was deceived in the expectation I had, that the golden colour would do so too; for, which way soever I turned the phial, either to or from the light, I found the liquor to appear always of a yellowish colour and no other. Upon this I imagined that the acid salts of the vinegar having been able to deprive the liquor of its ceruleous colour, a sulphureous salt being of a contrary nature, would be able to mortify the saline particles of vinegar, and destroy their effects; and accordingly having placed myself betwixt the window, and the phial, and into the same liquor dropt a few drops of oil of tartar per deliquium, (as chymists call it) I observed with pleasure, that immediately upon the diffusion of this liquor, the impregnated water was restored to its former ceruleous colour; and this liquor of tartar being very ponderous, and falling at first to the bottom of the phial, it was easy to observe that for a little while the lower part of the liquor appeared deeply ceruleous, whilst all the upper part retained its former yellowness, which it immediately lost as soon as either agitation or time had made a competent diffusion of the liquor of tartar through the body of the former tincture; and this restored liquor did, as it was looked upon against or from the light, exhibit the same phænomena as the tincted water did, before either of the adventitious liquors was poured into it.

HAVING made, Pyrophilus, divers trials upon this nephritick wood, we found mention made of it by the industrious Jesuit Kircberus, who having received a cup turned of it from the Mexican procurator of his society, has probably received also from him the information he gives us concerning that exotick plant; and therefore partly for that reason, and partly because what he writes concerning it, does not perfectly agree with what we have delivered, we shall not scruple to acquaint you in his own words, with as much of what he writes concerning our wood, as is requisite to our present purpose. Hoc loco (says he) neutiquam omittendum duximus quoddam ligni candidi Mexicani genus, quod indigenæ Coalle & Tlapazatli vocant, quod etsi experientia bucusque non nisi cœruleo aquam colore tingere docuerit, nos tamen continua experientia invenimus id aquam in omne colorum; genus transformare, quod merito cuipiam paradoxum videri posset; ligni frutex grandis, ut aiunt, non rarò in molem arboris excrescit, truncus illius est crassus, enodis, instar piri arboris, folia ciceris foliis, aut rutæ baud absimilia, flores exigui, ablongi, lutei & spicatim digesti; est frigida & humida planta, licet parum recedat à medio temperamento. Hujus itaque descriptæ arboris lignum in poculum efformatum, aquam eidem infusam primo in aquam intense cœuleam, colore floris buglossæ & quo diutius in eo steterit, tanto intensiorem colorem acquirit. Hanc igitur aquam si vitriæ sphæræ insuderis lucique exposueris, ne ullum quidem cærulei coloris vestigiam apparebit, sed instar aquæ pure putæ fontaæ limpidam claramque aspicientibus se præbebit. Porro si hanc phialam vitream versus locum magis umbrosum direxeris, totus humor gratissimum virorem reseret; si adhuc umbrosioribus locis, subrubrum, & sic pro rerum objectarum conditione, mirum dictu, colorem mutabit; in tenebris verò vel in vase opaco posita cœruleum colorem suum resumet.

IN this passage we may take notice of the following particulars. And first he calls it a white Mexican wood, whereas (not to mention that Movardes informs us that it is brought out of Nova Hispania) the wood that we have met with in several places, and employed as Lignum Nephriticum, was not white, but for the most part of a much darker colour, not unlike that of the sadder coloured wood of juniper. It is true, that Monardes himself also says, that the wood is white and it is affirmed, that the wood which is of a sadder colour is adulterated by being imbued with the tincture of a vegetable, in whose decoction it is steeped. But having purposely inquired of the eminentest of our English druggists, he peremptorily denied it. And indeed, having considered some of the fairest round pieces of this wood that I could meet with in these parts, I had opportunity to take notice that in one or two of them it was the external part of the wood that was white, and the more inward part that was of the other colour; the contrary of which would probably have appeared, if the wood had been adulterated after the aforementioned manner. And I have at present by me a piece of such wood, which for about an inch next the bark is white, and then, as it were, abruptly passes to the abovementioned colour; and yet this wood, by the tincture it afforded us in water, appears to have its coloured part genuine enough: for as for the white part, it appears, upon trial of both at once, much less enriched with the tingent property.

NEXT, whereas our author tells us, that the infusion of this wood exposed in a phial to the light, looks like spring-water, in which, he afterwards adds, that there is no tincture to be seen in it; our observation and his agree not: for the liquor which opposed to the darker part of a room exhibits a sky-colour, did constantly, when held against the light, appear yellowish or reddish, according as its tincture was more dilute or deep; and then, whereas it has been already said, that the ceruleous colour was by acid salts abolished, this yellowish one survived without any considerable alteration, so that unless our author's words be taken in a very limited sense, we must conclude, that either his memory misinformed him, or that his white nephritick wood, and the sadder coloured one which we employed, were not altogether of the same nature. What he mentions of the cup made of Lignum Nephriticum, we have not had opportunity to try, not having been able to procure pieces of that wood great enough, and otherwise fit to be turned into cups; but as for what he says in the title of his experiment, that this wood tinges the water with all sorts of colours, that is much more than any of those pieces of nephritick wood that we have hitherto employed, was able to make good; the change of colours discernable in a phial full of water, impregnated by any of them, as it is directed towards a place more lightsome or obscure, being far from affording a variety answerable to so promising a title. And as for what he tells us, that in the dark the infusion of our wood will resume a ceruleous colour, I wish he had informed us how he tried it.

BUT this brings into my mind, that having sometimes, for curiosity sake, brought a round phial with a long neck filled with the tincture of Lignum Nephriticum into the darkened room already often mentioned, and holding it sometimes in, sometimes near the sun-beams that entered at the hole, and sometimes partly in them, and partly out of them, the glass being held in several postures, and looked upon from several neighbourirg parts of the room, disclosed a much greater variety I colours than in ordinary enlightened rooms it is wont to do; exhibiting, besides the usual colours, a red in some parts, and a green in others, besides intermediate colours produced by the differing degrees, and odd mixtures of light and shade.

BY all this you may see, Pyrophilus, the reasonableness of what we elsewhere had occasion to mention, when we have divers times told you, that it is useful to have new experiments tried over again, though they were, at first, made by knowing and candid men; such reiterations of experiments commonly exhibiting some new phænomena, detecting some mistake, or hinting some truth, in reference to them, that was not formerly taken notice of. And some of our friends have been pleased to think, that we have made no unusual addition to this experiment, by shewing a way, how in a moment our liquor may be deprived of its blueness, and restored to it again by the affusion of a few drops of liquors, which have neither of them any colour at all of their own. And that which deserves some particular wonder, is, that the ceruleous tincture of our wood is subject by the former method to be destroyed or restored, the yellowish or reddish tincture continuing what it was. And that you may see, that salts are of a considerable use in the striking of colours, let me add to the many experiments which may be afforded us to this purpose by the dyers trade, this observation; that as far as we have hitherto tried, those liquors in general that are strong of acid salts have the power of destroying the blueness of the infusion of our wood, and those liquors indiscriminately that abound with sulphureous salts (under which I comprehend the urinous and volatile salts of animal substances, and the alcalizate or fixed salts that are made by incineration) have the virtue of restoring it.

THAT this experiment, Pyrophilus, may be as well useful as delightful to you, I must mind you, Pyrophilus, that in the newly mentioned observation, I have hinted to you a new and easy way of discovering in many liquors (for I dare not say in all) whether it be an acid or sulphureous salt, that is predominant; and that such a discovery is oftentimes of great difficulty, and may frequently be of great use, he that is not a stranger to the various properties and effects of salts, and of how great moment it is to be able to distinguish their tribes, may readily conceive. But to proceed to the way of trying other liquors by an infusion of our wood, take it briefly thus. Suppose I have a mind to try whether I conjecture aright, when I imagine that allom, though it be plainly a mixt body, does abound rather with acid than sulphureous salt: to satisfy myself herein, I turn my back to the light, and holding a small phial full of the tincture of Lignum Nephriticum, which, looked upon in that position, appears ceruleous, I drop into it a little of a strong solution of allom made in fair water; and finding upon the affusion and shaking of this new liquor, that the blueness formerly conspicuous on our tincture does presently vanish, I am thereby incited to suppose, that the salt predominant in allom belongs to the family of sour salts. But if on the other side I have a mind to examine whether or no I rightly conceive that salt of urine, or of hartshorn is rather of a saline sulphureous (if I may so speak) than of an acid nature, I drop a little of the saline spirit of either into the nephritic tincture, and finding that the ceruleous colour is rather thereby deepened than destroyed, I collect that the salts, which constitute these spirits, are rather sulphureous than acid. And to satisfy myself yet farther in this particular, I take a small phial of fresh tincture, and placing both it and myself in reference to the light as formerly, I drop into the infusion just as much distilled vinegar, or other acid liquor as will serve to deprive it of its blueness (which a few drops, if the sour liquor be strong, and phial small, will suffice to do;) then without changing my posture, I drop and shake into the same phial a small proportion of spirit of hartshorn or urine, and finding that upon this affusion the tincture immediately recovers its ceruleous colour, I am thereby confirmed in my former opinion, of the sulphureous nature of these salts. And so, whereas it is much doubted by some modern chymists to what sort of salt, that which is predominant in quick-lime belongs, we have been persuaded to refer it rather to lixiviate than acid salts; and having observed, that though an evaporated infusion of it will scarce yield such a salt, as ashes and other alcalizate bodies are wont to do, yet if we deprive our nephritic tincture of its blueness by just so much distilled vinegar as is requisite to make that colour vanish, the lixivium of quick-lime will immediately upon its affusion recall the banished colour, but not so powerfully as either of the sulphureous liquors formerly mentioned. And therefore I allow myself to guess at the strength of the liquors examined by this experiment, by the quantity of them which is sufficient to destroy or restore the ceruleous colour of our tincture. But whether concerning liquors, wherein neither acid nor alcalizate salts are eminently predominant, our tincture will enable us to conjecture any thing more than that such salts are not predominant in them, I take not upon me to determine here, but leave to further trial; for I find not that spirit of wine, spirit of tartar freed from acidity, or chymical oil of turpentine (although liquors which must be conceived very saline, if chymists have, which is here no place to dispute, rightly ascribed tastes to the saline principle of bodies) have any remarkable power either to deprive our tincture of its ceruleous colour, or restore it, when upon the affusion of spirit of vinegar it has disappeared.

AND here I must not omit, Pyrophilus, to inform you, that we can shew you even in a mineral body something that may seem very near of kin to the changeable quality of the tincture of Lignum Nephriticuni, for we have several flat pieces of glass, of the thickness of ordinary panes for windows, one of which being interposed betwixt the eye and a clear light, appears of a golden colour, not much unlike that of the moderate tincture of our wood; but being so looked upon as that the beams of light are not so much trajected through it as reflected from it to the eve, that yellow seems to degenerate into a pale blue, somewhat like that of a turquoise. And that which may also appear strange, is, that if in a certain posture you hold one of these perpendicular to the horizon, so that the sun beams shine upon half of it, the other half being shaded, you may see that the part shined upon will be of a much diluter yellow than the shaded part, which will appear more richly coloured; and if you alter the posture of the glass, so that it be not held perpendicular, but parallel in reference to the horizon, you may see (which perhaps you will admire) the shaded part look of a golden colour, but the other that the sun shines freely on, will appear considerably blue, and as you remove any part of the glass thus held horizontally into the sun-beams or shade, it will in the twinkling of an eye seem to pass from one of the above mentioned colours to the other; the sun-beams trajected through it upon a sheet of white paper held near it, do colour it with yellow, somewhat bordering upon a red, but yet the glass may be so opposed to the sun, that it may upon paper project a mixed colour here and there more inclined to yellow, and here and there more to blue. The other phænomena of this odd glass, I fear it would be scarce worth while to record; and therefore I shall rather advertise you, first, that in the trying of these experiments with it, your must take notice that one of the sides has either alone, or at least principally, its superficial parts disposed to the reflection of the blue colour above named, and that therefore you must have a care to keep that side nearest to the eye. And next, that we have ourselves made glasses not unfit to exhibit an experiment not unlike that I have been speaking of, by laying upon pieces of glass some very finely foliated silver, and giving it by degrees a much stronger fire than is requisite or usual for the tinging of glasses of other colours. And this experiment, not to mention that it was made without a furnace, in which artificers that paint glass are wont to be very curious, is the more considerable, because, that though a skilful painter could not deny to me that it was with silver he coloured his glasses yellow; yet he told me, that when to burn them (as they speak) he lays on the plates of glass nothing but a calx of silver calcined without corrosive liquors, and tempered with fair water, the plates are tinged of a fine yellow that looks of a golden colour, which part soever of it you turn to or from the light; whereas (whether it be what an artificer would call over-doing, or burning, or else the employing the silver crude that makes the difference) we have found more than once, that some pieces of glass prepared as we have related, though held against the light they appeared of a transparent yellow, yet looked on with one's back turned to the light, they exhibited an untransparent blue.

IF you will allow me, Pyrophilus, for the avoiding of ambiguity, to employ the word pigments, to signify such prepared materials (as cochineal, vermilion, orpiment) as painters, dyers, and other artificers make use of to impart or imitate particular colours; I shall be the better understood in divers passages of the following papers, and particularly when I tell you, that the mixing of pigments being no inconsiderable part of the painters art, it may seem an incroachment in me to meddle with it. But I think I may easily be excused (though I do not altogether pass it by) if I restrain myself to the making of a transient mention of some few of their practices about this matter; and that only so far forth, as may warrant me to observe to you, that there are but few simple and primary colours (if I may so call them) from whose various compositions all the rest do as it were result. For though painters can imitate the hues (though not always the splendor) of those almost numberless, differing colours that are to be met with in the works of nature, and of art, I have not yet found, that to exhibit this strange variety they need employ any more than white, and black, and red, and blue, and yellow; these five, variously compounded, and (if I may so speak) decompounded, being sufficient to exhibit a variety and number of colours, such as those that are altogelther strangers to the painters pallets can hardly imagine.

THUS (for instance) black and white differingly mixed, make a vast company of lighter and darker greys.

BLUE and yellow make a huge variety of greens.

RED and yellow make orange-tawny.

RED with a little white makes a carnation.

RED with an eye of blue, makes a purple, and by these simple compositions again compounded among themselves, the skilful painter can produce what kind of colour he pleases, and a great many more than we have yet names for. But, as I intimated above, it is not my design to prosecute this subject, though I thought it not unfit to take some notice of it, because we may hereafter have occasion to make use of what has been now delivered, to illustrate the generation of intermediate colours; concerning which we must yet subjoin this caution, that to make the rules about the emergency of colours fit to be relied upon, the corpuscles whereof the pigments consist must be such as do not destroy one another's texture; for in case they do, the produced colour may be very different from that which would result from the mixture of other harmless pigments of the same colours, as I shall have occasion to shew ere long.

IT may also give much light to an inquirer into the nature of colours, to know that not only in green, but in many (if not all) other colours, the light of the sun passing through diaphanous bodies of differing hues may be tinged of the same compound colour, as if it came from some painters colours of the same denomination, though this latter be exhibited by reflection, and be (as the former experiment declares) manifestly compounded of material pigments. Wherefore to try the composition of colours by trajection, we provided several plates of tinged glass, which being laid two at a time, one on the top of another, the object looked upon through them both, appeared of a compounded colour, which agrees well with what we have observed in the second experiment, of looking against the light through differingly coloured papers. But we thought the experiment would be more satisfactory, if we procured the sun-beams to be so tinged in their passage through plates of glass, as to exhibit the compounded colour upon a sheet of white paper. And though by reason of the thickness of the glasses, the effect was but faint, even when the sun was high and shined forth clear, yet, we easily remedied that by contractng the beams we cast on them by means of a convex burning-glass, which, where it made the beams much converge, increased the light enough to make the compounded colour very manifest upon the paper. By this means we observed, that the beams trajected through blue and yellow, composed a green; that an intense and moderate red did with yellow make differing degrees of saffron, and orange-tawny colours; that green and blue made a colour partaking of both, such as that which some Latin writers call Pavonaceus that red and blue made a purple; to which we might add other colours, that we produced by the combinations of glasses differingly tinged, but that I want proper words to express them in our language, and had not, when we made the trials, the opportunity of consulting with a painter, who perchance might have supplied me with some of the terms I wanted.

I KNOW not whether it will be requisite to subjoin on this occasion, what I tried concerning reflections from coloured glasses, and other transparent bodies; namely, that having exposed four or five sorts of them to the sun, and cast the reflected beams upon white paper held near at hand, the light appeared not manifestly tinged, but as if it had been reflected from the impervious parts of a colourless glass; only that reflected from the yellow was here and there stained with the same colour, as if those beams were not all reflected from the superficial, but some from the internal parts of the glass, upon which occasion you may take notice, that a skilful tradesman, who makes such coloured glass, told me, that whereas the red pigment was but superficial, the yellow penetrated to the very midst of the plate. But for further satisfaction, not having the opportunity to foliate those plates, and so turn them into looking-glasses, we foliated a plate of Muscovy glass, and then laying on it a little transparent varnish of a gold colour, we exposed it to the sun-beams, so as to cast them upon a body fit to receive them; on which the reflected light appearing, as we expected, yellow, manifested that rebounding from the specular part of the selenitis it was tinged in its return with the colour of the transparent varnish through which it passed.

AFTER what we have said of the composition of colours, it will now be seasonable to annex some experiments that we made in favour of those colours, that are taught in the schools not to be real, but only apparent and fantastical; for we found by trials, that these colours might be compounded, both with true and stable colours, and with one another, as well as unquestionably genuine and lasting colours, and that the colours resulting from such compositions, would respectively deserve the same denominations.

FOR first, having by the trajection of the sun-beams through a glass prism thrown an iris on the floor, I found that by placing a blue glass at a convenient distance betwixt the prism and the iris, that part of the iris that was before yellow, might be made to appear green, though not of a grass green, but of one more dilute and yellowish. And it seems not improbable, that the narrow greenish list (if I may so call it) that is wont to be seen between the yellow and blue parts of the iris, is made by the confusion of those two bordering colours.

NEXT, I found, that though the want of a sufficient liveliness in either of the compounding colours, or a light error in the manner of making the following trials, was enough to render some of them unsuccessful, yet, when all necessary circumstances were duly observed, the event was answerable to our expectation and desire.

AND (as I formerly noted) that red and blue compound a purple, so I could produce this last named colour, by casting at some distance from the glass the blue part of the prismatical iris (as I think it may be called for distinction sake) upon a lively red (or else the experiment succeeds not so well.) And I remember, that sometimes when I tried this upon a piece of red cloth, that part of the iris which would have been blue, (as I tried by covering that part of the cloth with a piece of white paper) and compounded with the red, wherewith the cloth was imbued before, appeared of a fair purple, did, when I came to view it near at hand, look very oddly, as if there were some strange reflection or refraction, or both, made in the hairs of which that cloth was composed.

CASTING likewise the prismatical iris upon a very vivid blue, I found that part of it, which would else have been the yellow, appear green. (Another somewhat differing trial, and yet fit to confirm this, you will find in the fifteenth experiment.)

BUT it may seem somewhat more strange, that though the prismatical iris being made by the refraction of light through a body that has no colour at all, must according to the doctrine of the schools, consist of as purely emphatical colours as may be, yet even these may be compounded with one another, as well as real colours in the grossest pigments. For I took at once two triangular glasses, and one of them being kept fixt in the same posture, that the iris it projected on the floor might not waver, I cast on the same floor another iris with the other prism, and moving it to and fro to bring what part of the second iris I pleased, to fall upon that part of the first I thought fit, we did sometimes (for a small error suffices to hinder the success) obtain by this means a green colour in that part of the more stable iris, that before was yellow, or blue; and frequently by casting those beams, that in one of the irises made the blue upon the red parts of the other iris, we were able to produce a lovely purple, which we can destroy or recompose at pleasure, by invering and re-approaching the edges of the two irises

ON this occasion, Pyrophilus, I shall add, that finding the glass prism to be the usefullest instrument men have yet employed about the contemplation of colours, and considering that prisms, hitherto in use, are made of glass transparent and colorless, I thought it would not be amiss to try, what change the superinduction of a colour, without the destruction of the diaphinaity, would produce in the colours exhibited by the prism. But being unable to procure one to be made of coloured glass, and fearing also that if it were not carefully made, the thickness of it would render it too opacous, I endeavoured to substitute one made of clarified rosin, or of turpentine brought (as I elsewhere teach) to the consistence of a transparent gum. But though these endeavors were not wholly lost, yet we found it so difficult to give these materials their true shape, that we chose rather to varnish over an ordinary prism with some of those few pigments that are to be had transparent; as accordingly we did first with yellow, and then with red, or rather crimson, made with lake tempered with a convenient oil; and the event was, that for want of good transparent colours (of which you know there are but very few) both the yellow and the red made the glass so opacous (thought the pigment were laid on but upon two sides of the glass, no more being absolutely necessary) that unless I looked upon an enlightened window, or the flame of a candle, or some other luminous very vivid object, I could scarce discern any colours at all, especially when the glass was covered with red. But when I did look on such objects, it appeared (as I expected) that the colour of the pigment had vitiated or drowned some of those which the prism would, according to its wont, have exhibited, and mingling with others, altered them: as I remember, that both to, my eyes, and others to whom I shewed it, when the prism was covered with yellow, it made those parts of bright objects, where the blue would else have been conspicuous, appear of a light green. But Pyrophilus both the nature of the colours, and the degree of transparency, or of darkness in the pigment, besides divers other circumstances, did so vary the phænomena of these trials, that till I can procure small coloured prisms, or hollow ones that may be filled with tincted liquor, or obtain some better pigments than those I was reduced to employ. I shall forbear to build any thing upon what has been delivered, and shall make no other use of it, than to invite you to prosecute the enquiry further.

AND here, Pyrophilus, since we am treating of emphatical colours, we shall add what we think not unworthy your observation, and not unfit to afford some exercise to the speculative. For there are some liquors which, though colourless themselves, when they came to be elevated, and dispersed into exhalations, exhibit a conspicuous colour, which they lose again, when they come to be reconjoined into a liquor; as good spirit of nitre, or upon its account strong aqua fortis, though devoid of all appearance of redness whilst they continue in the form of a liquor, if a little heat chance to turn the minute parts of them into vapours, the steam will appear of a reddish or deep yellow colour, which will vanish when those exhalations come to resume the form of a liquor.

And not only if you look upon a glass half full of aqua fortis, or spirit of nitre, and half full of nitrous steams proceeding from it, you will see the upper part of the glass of the colour freshly mentioned, if through it you look upon the light: but which is much more considerable, I have tried, that putting aqua fortis in a long clear glass, and adding a little copper or some such open metal to it, to excite heat and fumes, the light trajected through those fumes, and cast upon a sheet of white paper, did upon that appear of the colour that the fumes did, when directly looked upon, as if the light were as well tinged in its passage through these fumes, as it would have been by passing through some glass or liquor in which the same colour was inherent.

To which I shall further add, that having sometimes had the curiosity to observe whether the beams of the sun near the horizon, trajected through a very red sky, would not (though such rednesses are taken to be but emphatical colours) exhibit the like colour; I found that the beams falling within a room upon a very white object, placed directly opposite to the sun, disclosed a manifest redness, as if they had passed through a coloured medium.

THE emergency, Pyrophilus, of colours upon the coalition of the particles of such bodies as were neither of them of the colour of that mixture whereof they are the ingredients, is very well worth our attentive observation, as being of good use both speculative and practical: for much of the mechanical use of colours among painters and dyers doth depend upon the knowledge of what colours may be produced by the mixtures of pigments so and so coloured. And (as we lately intimated) it is of advantage to the contemplative Naturalist, to know how many and which colours are primitive (if I may so call them) and simple, because it both eases his labour by confining his most solicitous enquiry to a small number of colours upon which the rest depend, and assists him to judge of the nature of particular compound colours, by shewing him, from the mixture of what more simple ones, and of what proportions of them to one another, the particular colour to be considered does result. But because, to insist on the proportions, the manner and the effects of such mixtures, would oblige me to consider a greater part of the painter's art and dyer's trade, than I am well acquainted with, I confined myself to make trial of several ways to produce green by the composition of blue and yellow: and shall in this place both recapitulate most of the things I have dispersedly delivered already concerning that subject and recruit them.

AND first whereas painters (as I noted above) are wont to make green by tempetering blue and yellow, both of them made into a soft consistence, with either water or oil, some liquor of kin to one of those two, according as the picture is to be drawn with those they call water-colours, or those they term oil-colours; I found, that by chusing fit ingredients, and mixing them in the form of dry powders, I could do, what I could not if the ingredients were tempered up with liquor: but the blue and yellow powders must not only be finely ground, but such as that the corpuscles of the one may not be too unequal to those of the other, left by the disproportionate minuteness the smaller cover and hide the greater. We used with good success a slight mixture of the fine powder of bise, with that of orpiment, or that of good yellow oker; I say, a slight mixture, because we found that an exquisite mixture did not do so well: but by lightly mingling the two pigments in several little parcels those of them in which the proportion and manner of mixture was more lucky, afforded us a good green.

2. WE also learned in the dye-houses, that cloth being dyed blue with woad, is afterwards by the yellow decoction of woud-wax or wood-wax dyed into a green colour.

3. YOU may also remember what we above related, where we intimated, that having in a darkened room taken two bodies, a blue and a yellow, and cast the light reflected from the one upon the other, we likewise obtained a green.

4. AND you may remember, that we observed a green to be produced, when in the same darkened room we looked at the hole at which alone the light entered, through the green and yellow parts of a sheet of marbled paper laid over one another.

5. WE found too, that the beams of the sun being trajected through two pieces of glass, the one blue and the other yellow, laid over one another, did upon a sheet of white paper, on which they were made to fall, exhibit a lovely green.

6. I HOPE also, that you have not already forgot, what was so lately delivered, concerning the composition of a green, with a blue and yellow: of which most authors would call the one a real, and the other an emphatical.

7. AND I presume, you may have yet fresh in your memory, what the fourteenth experiment informs you, concerning the exhibiting of a green, by the help of a blue and yellow, that were both of them emphatical.

8. WHEREFORE we will proceed to take notice, that we also devised a way of trying whether or no metalline solutions, though one of them at least had its colour adventitious, by the mixture of the menstruum employed to dissolve it, might not be made to compound a green after the manner of other bodies. And though this seemed not easy to be performed by reason of the difficulty of finding metalline solutions of the colour requisite, that would mix without precipitating each other; yet after a while having considered the matter, the first trial afforded me the following experiment. I took a high yellow solution of good gold in aqua regis (made of aqua fortis, and as I remember half its weight of spirit of salt); to this I put a due proportion of a deep and lovely blue solution of crude copper (which I have elsewhere taught to be readily dissolvable in strong spirit of urine.) And these two liquors, though at first they seemed a little to curdle one another, yet being thoroughly mingled by shaking they presently, as had been conjectured, united into a transparent green liquor, which continued so for divers days, that I kept it in a small glass wherein it was made, only letting fall a little blackish powder to the bottom. The other phænomena of this experiment belong not to this place, where it may suffice to take notice of the production of a green, and that the experiment was more than once repeated with success.

9. AND lastly, to try whether this way of compounding colours would hold even in ingredients actually melted by the violence of the fire, provided their texture were capable of safely enduring fusion, we caused some blue and yellow ammel to be long and well wrought together in the flame of a lamp, which being strongly and incessantly blown on them, kept them in some degree of fusion, and at length (for the experiment requires some patience as well as skill) we obtained the expected ammel of a green colour.

I KNOW not, Pyrophilus, whether it be worth while to acquaint you with the ways that came into my thoughts, whereby in some measure to explicate the first of the mentioned ways of making a green; for I have sometimes conjectured, that the mixture of the bise and the orpiment produced a green by so altering the superficial asperity, which each of those ingredients had apart, that the light incident on the mixture was reflected with differing shades, as to quantity, or order, or both, from those of either of the ingredients, and such as the light is wont to be modified with, when it reflects from grass, or leaves, or some of those other bodies that we are wont to call green. And sometimes too I have doubted, whether the produced green might not be partly at least derived from this, that the beams that rebound from the corpuscles of the orpiment, giving one kind of stroke upon the retina, whose perception we call yellow, and the beams reflected from the corpuscles of the bise giving another stroke upon the same retina, like to objects that are blue; the contiguity and minuteness of these corpuscles may make the appulse of the reflected light fall upon the retina within so narrow a compass, that the part they beat upon being as it were a physical point, they may give a compounded stroke, which may consequently exhibit a compounded and new kind of sensation: as we see that two strings of a musical instrument being struck together, making two noises that arrive at the ear at the same time as to sense, yield a sound differing from either of them, and as it were compounded of both; insomuch that if they be discordantly tuned, though each of them struck apart would yield a pleasing sound, yet being struck together they make but a harsh and troublesome noise. But this not being so fit a place to prosecute speculations, I shall not insist, neither upon these conjectures nor any others, which the experiment we have been mentioning may have suggested to me. And I shall leave it to you, Pyrophilus, to derive what instruction you can from comparing together the various ways whereby a yellow and a blue can be made to compound a green: that which I now pretend to, being only to shew that the first of those mentioned ways (not to take at present notice of the rest) does far better agree with our conjectures about colours, than either with the doctrine of the schools, or with that of the chymists, both which seem to be very much disfavoured by it.

FOR first, since in the mixture of the two mentioned powders I could by the help of a very excellent microscope (for ordinary ones will scarce serve the turn) discover that which seemed to the naked eye a green body, to be but a heap of distinct, though very small grains of yellow orpiment and blue bise confusedly enough blended together, it appears that the coloured corpuscles of either kind did each retain its own nature and colour; by which it may be guessed, what meer transposition and juxtaposition of minute and singly unchanged particles of matter can do to produce a new colour. For that this local motion and new disposition of the small parts of the orpiment did intervene, is much more manifest than it is easy to explicate how they should produce this new green, otherwise than by the new manner of their being put together, and consequently by their new disposition to modify the incident light, by reflecting it otherwise than they did before they were mingled together.

SECONDLY, The green thus made, being (if I may so speak) mechanically produced, there is no pretence to derive it from I know not what incomprehensible substantial form, from which yet many would have us believe that colours must flow; nor does this green, though a real and permanent, not a phantastical and vanid colour, seem to be such an inherent quality as they would have it, since not only each part of the mixture remains unaltered in colour, and consequently of a differing colour from the heap they compose; but if the eye be assisted by a microscope to discern things better and more distinctly than before it could, it sees not a green body, but a heap of blue and yellow corpuscles.

AND in the third place, I demand what either sulphur, or salt, or mercury has to do in the production of this green; for neither the bise nor the orpiment were endued with that colour before; and the bare juxtaposition of the corpuscles of the two powders that work not upon each other, but might, if we had convenient instruments, be separated, unaltered, cannot, with any probability, be imagined either to increase or diminish any of the three hypostatical principles (to which of them soever the chymists are pleased to ascribe colours); nor does there here intervene so much as heat to afford them any colour to pretend, that at least there is made an extraversion (as the Helmontians speak) of the sulphur, or of any of the two other supposed principles. But upon this experiment we have already reflected enough, if not more than enough for once.

BUT here, Pyrophilus, I must advertise you, that it is not every yellow and every blue that, being mingled, will afford a green; for in case one of the ingredients do not act only as endowed with such a colour, but as having a power to alter the texture of the corpuscles of the other, so as to indispose them to reflect the light, as corpuscles that exhibit a blue or a yellow are wont to reflect it; the emergent colour may be not green, but such as the change of texture in the corpuscles of one or both of the ingredients qualifies them to shew forth: as for instance, if you let fall a few drops of syrup of violets upon a piece of white paper, though the syrup being spread will appear blue, yet mingling with it two or three drops of the lately mentioned solution of gold, I obtained not a green but a reddish mixture, which I expected from the remaining power of the acid salts abounding in the solution, such salts or saline spirits being wont, as we shall see anon, though weakened, so to work upon that syrup as to change it into a red or reddish colour. And to confirm that for which I allege the former experiment, I shall add this other, that having made a very strong and high-coloured solution of filings of copper with spirit of urine, though the menstruum seemed glutted with the metal, because I put in so much filings, that many of them remained for divers days undissolved at the bottom; yet having put three or four drops of syrup of violets upon white paper, I found that the deep blue solution proportionably mingled with this other blue liquor, did not make a blue mixture, but, as I expected, a fair green, upon the account of the urinous salt that was in the menstruum.

TO shew the chymists, that colours may be made to appear or vanish, where there intervenes no accession or change either of the sulphureous, or the saline, mercurial principle (as they speak) of bodies; I shall not make use of the iris afforded by the glass-prism, nor of the colours to be seen in a fair morning in those drops of dew that do in a convenient manner reflect and refract the beams of light to the eye: but I will rather mind them of what they may observe in their own laboratories, namely, that divers, if not all, chymical essential oils, as also good spirit of wine, being shaken till they have good store of bubbles, those bubbles will (if attentively considered) appear adorned with various and lovely colours, which all immediately vanish, upon the relapsing of the liquor that affords those bubbles their skins, into the rest of the oil, or spirit of wine; so that a colourless liquor may be made in a trice to exhibit variety of colours, and may lose them in a moment without the accession or diminution of any of its hypostatical principles. And, by the way, it is not unworthy our notice, that some bodies, as well colourless as coloured, by being brought to a great thinness of parts, acquire colours though they had none before, or colours differing from them they were before endued with: for, not to insist on the variety of colours, that water, made somewhat glutinous by soap, acquires when it is blown into such spherical bubbles as boys are wont to make and play with; turpentine (though it have a colour deep enough of its own) may (by being blown into after a certain manner) be brought to afford bubbles adorned with variety of orient colours, which though they vanish some while upon the breaking of the bubbles, yet they would in all likelihood always exhibit colors upon their superficies (though not always the same in the same parts of them, but varied according to the incidence of the sight, and the position of the eye) if their texture were durable enough. For I have seen one that was skilled at fashioning glasses by the help of a lamp, blowing some of them so strongly as to burst them; whereupon it was found, that the tenacity of the metal was such, that before it broke, it suffered itself to be reduced into films so extremely thin, that being kept clean they constantly shewed on their surfaces (but after the manner newly mentioned) the varying colours of the rainbow, which were exceedingly vivid, as I had often opportunity to observe in some, that I caused purposely to be made, to keep by me.

BUT lest it should be objected, that the above-mentioned instances are drawn from transparent liquors, it may possibly appear not impertinent to add, what I have sometimes thought upon, and several times tried, when I was considering the opinions of the chymists about colours. I took then a feather of a convenient bigness and shape, and holding it at a fit distance betwixt my eye and the sun when he was near the horizon, methought there appeared to me a variety of little rainbows, with differing and very vivid colours, of which none was constantly to be seen in the feather; the like phenomenon I have at other times (though not with altogether so good success) produced, by interposing at a due distance a piece of black ribband betwixt the almost setting sun and my eye; not to mention the trials I have made to the same purpose, with other bodies.

TAKE good syrup of violets, impregnated with the tincture of the flowers, drop a little of it upon a white paper (for by that means the change of colour will be more conspicuous, and the experiment may be practiced in smaller quantities) and on this liquor let fall two or three drops of spirit either of salt or vinegar, or almost any other eminently acid liquor, and upon the mixture of these you shall find the syrup immediately turned red: and the way of effecting, such a change has not been unknown to divers persons, who have produced the like, by spirit of vitriol, or juice of lemons, but have groundlessly ascribed the effect to some peculiar quality of those two liquors, whereas (as we have already intimated) almost any acid salt will turn syrup, of violets red. But to improve the experiment, let me add what has not (that I know of) been hitherto observed, and has, when we first shewed it them, appeared something strange, even to those that have been inquisitive into the nature of, colours; namely, that if instead of spirit of salt, or that of vinegar, you. drop upon the syrup of violets a little oil of tartar per deliquium, or the like quantity of solution of pot-ashes, and rub them together with your finger, you shall find the blue colour of the syrup turned in a moment into a perfect green; and the like may be performed by divers other liquors, as we may have occasion elsewhere to inform you.

THE use of what we lately delivered concerning the way of turning syrup of violets red or green, may be this; that, though it be a far more common and procurable liquor than the infusion of lignum nephriticum, it may yet be easily substituted in its room, when we have a mind to examine, whether or no the salt predominant in a liquor or other body, wherein it is loose and abundant, belong to the tribe of acid salts or not. For if such a body turn the syrup of a red or reddish purple colour, it does for the most part argue the body (especially if it be a distilled liquor) to abound with acid salt. But if the syrup be made green, that argues the predominant salt to be of a nature repugnant to that of the tribe of acids. For, as I find that either spirit of salt, or oil of vitriol, or aqua fortis, or spirit of vinegar, or juice of lemons, or any of the acid liquors I have yet had occasion to try, will turn syrup of violets of a red, or at least of a reddish colour; so I have found, that not only the volatile salts of all animal substances I have used, as spirit of hartshorn, of urine, of sal armoniac, of blood, &c. but also all the alcalizate salts I have employed, as the solution of salt of tartar, of potashes, of common wood-ashes, lime-water, &c. will immediately change the blue syrup into a perfect green. And by the same way (to hint that upon the by) I elsewhere show you, both the changes that nature and time produce, in the more saline parts of some bodies, may be discovered, and also how even such chymically prepared bodies, as belong not either to the animal kingdom, or to the tribe of alcalies, may have their new and superinduced nature successfully examined. In this place I shall only add, that not alone the changing the colour of the syrup requires, that the changing body be more strong of the acid, or other sort of salt, that is predominant in it, than is requisite for the working upon the tincture of lignum nephriticum; but that in this also, the operation of the formerly mentioned salts upon our syrup, differs from their operation upon our tinctures; that in this liquor, if the ceruleous colour be destroyed by an acid salt, it may be restored by one that is either volatile, or lixiviate; whereas in syrup of violets, though one of these contrary salts will destroy the action of the other, yet neither of them will restore the syrup to its native blue; but each of them will change it into the colour which itself doth (if I may so speak) affect, as we shall have occasion to shew in the notes on the twenty-fifth experiment.

THERE is a weed, more known to plowmen than beloved by them, whose flowers from their colour are commonly called blue-bottles, and corn-weed from are their growing among corn. These flowers, some ladies do, upon the account of their lovely colour, think worth the being candied, which when they are, they will long retain so fair a colour, as makes them a very fine sallad in the winter. But I have tried, that when they are freshly gathered, they will afford a juice, which when newly expressed (for in some cases it will soon enough degenerate) affords a very deep and pleasant blue. Now (to draw this to our present scope) by dropping on this fresh juice a little spirit of salt (that being the acid spirit I had then at hand) it immediately turned (as I predicted) into a red. And if, instead of the sour spirit, I mingled with it a little strong solution of an alcalizate salt, it did presently disclose a lovely green; the same changes being, by those differing sorts of saline liquors, producible in this natural juice, that we lately mentioned to have happened to that factitious mixture, the syrup of violets. And I remember, that finding this blue liquor, when freshly made, to be capable of serving in a pen for an ink of that colour, I attempted by moistening one part of a piece of white paper with the spirit of salt I have been mentioning and another with some alcalizate or volatile liquor, to draw a line on the leisurly dried paper, that should even before the ink was dry appear partly blue, partly red, and partly green: but though the latter part of the experiment succeeded not well (whether because volatile salts are too fugitive to be retained in the paper, and alcalizate ones are too unctuous, or so apt to draw moisture from the air, that they keep the paper from drying well) yet the former part succeeded well enough; the blue and the red being conspicuous enough to afford a surprizing spectacle to those, I acquaint not with (what I willingly allow you to call) the trick.

BUT lest you should be tempted to think (Pyrophilus) that volatile or alcalizate salts change blues into green, rather upon the score of the easy transition of the former colour into the latter, than upon the account of the texture, wherein most vegetables, that afford a blue, seem, though otherwise differing, to be allied; I will add, that when I purposely dissolved blue vitriol in fair water, and thereby imbued sufficiently that liquor with that colour, a lixiviate liquor, and a urinous salt being copiously poured upon distinct parcels of it, did each of them, though perhaps with some difference, turn the liquor not green, but of a deep yellowish colour, almost like that of yellow oker; which colour, the precipitated corpuscles retained, when they had leisurely subsided in the bottom. What this precipitated substance is, it is not needful now to inquire in this place, and in another I have shewn you, that notwithstanding its colour, and its being obtainable from an acid menstruum by the help of salt of tartar, it is yet far enough from being the true sulphur of vitriol.

OUR next experiment (Pyrophilus) will perhaps seem to be of a contrary nature to the two former, made upon syrup of violets and juice of blue-bottles. For as in them, by affusion of oil of tartar, a bluish liquor is made green, so in this, by the sole mixture of the same oil, a greenish liquor becomes blue. The hint of this experiment was given us by the practice of some Italian painters, who being wont to counterfeit Ultra-marine Azure (as they call it) by grinding verdigrease with sal-armoniac, and some other saline ingredients, and letting them rot (as they imagine) for a good while together in a dunghill, we supposed that the change of colour wrought in the verdigrease by this way of preparation must proceed from the action of certain volatile and alcalizate salts, abounding in some of the mingled concretes, and brought to make a further dissolution of the copper abounding in the verdigrease; and therefore we conjectured, that if both the verdigrease, and such salts were dissolved in fair water, the small parts of both being therein more subdivided and set at liberty, would have better access to each other, and thereby incorporate much the more suddenly. And accordingly we found, that if upon a strong solution of good French verdigrease (for it is that we are wont to employ, as the best) you pour a just quantity of oil of tartar, and shake them well together, you shall immediately see a notable change of colour, and the mixture will grow thick, and not transparent; but if you stay a while till the grosser part be precipitated to, and settled in the bottom, you may obtain a clear liquor of a very lovely colour, and exceeding delightful to the eye. But, you must have a care to drop in a competent quantity of oil of tartar, for else the colour will not be so deep and rich; and if instead of this oil you employ a clear lixivium of pot-ashes, you may have an azure somewhat lighter or paler than, and therefore differing from, the former. And if instead of either of these liquors, you make use of spirit of urine, or of hartshorn, you may, according to the quantity and quality of the spirit you pour in, obtain some further variety (though scarce considerable) of ceruleous liquors. And yet lately by the help of this urinous spirit we made a blue liquor, which not a few ingenious persons, and among them, some, whose profession makes thern very conversant with colours, have looked upon with some wonder. But these azure-coloured liquors should be freed from the subsiding matter, which the salts of tartar or urine precipitate out of them, rather by being decanted, than by filtration. For by the latter of these ways, we have sometimes found the colour of them very much impaired, and little superior to that of the grosser substance, that is left in the filtre.

THAT roses held over the fume of sulphur, may quickly by it be deprived of their colour, and have as much of their leaves, as the fume works upon, burned pale, is an experiment, that divers others have tried, as well as I. But (Pyrophilas) it may seem somewhat strange to one that has never considered the compounded nature of brimstone, that whereas the fume of sulphur will, as we have said, whiten the leaves of roses; that liquor, which is commonly called, oil of sulphur per campanam, because it is supposed to be made by the condensation of these fumes, in glasses shaped like bells, into a liquor, does powerfully heighten the tincture of red roses, and make it more red and vivid, as we have easily tried by putting some red-rose leaves, that had been long dried (and so had lost much of their colour) into a phial of fair water. For a while after the affusion. of a convenient quantity of the liquor we are speaking of, both the leaves themselves, and the water they were steeped in, discovered a very fresh and lovely colour.

IT may (Pyrophilus) somewhat serve to illustrate, not only the doctrine of pigments, and of colours, but divers other parts of the corpuscular philosophy, as that explicates odours, and many other things, not as the schools by airy qualities, but by real, though extremely minute bodies; to examine, how much of the colourless; liquor a very small parcel of a pigment may imbue with a discernable colour. And though there be scarce any thing of preciseness to be expected from such trials, yet I presumed, that (at least) I should be able to show a much further subdivision of the parts of matter into visible particles, than I have hitherto found taken notice of, and than most men would imagine; nobody, that, I know of, having yet attempted to reduce this matter to any measure.

THE bodies, the most promising for such a purpose, might seem to be the metals, especially gold, because of the multitude and minuteness of its parts, which might be argued from the incomparable closeness of its texture: but though we tried a solution of gold made in aqua regia first, and then in fair water, yet in regard we were to determine the pigment we employed, not by bulk, but weight, and because also, that the yellow colour of gold is but a faint one In comparison of the deep colour of cochineal, we rather chose this to make our trials with. But among divers of these it would suffice to set down one, which was carefully made in vessels conveniently shaped, (and that in the presence of a witness, and an assistant) the sum whereof I find among my Adversaria, registered in the following words. To which I shall only premise, (to lessen the wonder of so strange a diffusion of the pigment) that cochineal will be better dissolved, and have its colour far more heightened by spirit of urine, than (I say not by common water, but) by rectified spirit of wine itself.

THE note I spoke of is this: [One grain of cochineal dissolved in a pretty quantity of spirit of urine, and then dissolved further by degrees in fair water, imparted a discernable, though but a very faint colour, to about six glass fulls of water, each of them containing about forty three ounces and a half, which amounts to above a hundred twenty five thousand times its own weight.]

IT may afford a considerable hint (Pyrophilus) to him, that would improve the art of dying, to know what change of colours may be produced by the three several sorts of salts already often mentioned, (some or other of which may be procured in quantity at reasonable rates) in the juices, decoctions, infusions, and (in a word) the more soluble parts of vegetables. And, though the design of this discourse be the improvement of knowledge, not of trades; yet thus much I shall not scruple to intimate here, that the blue liquors, mentioned in the twentieth and one and twentieth experiments, are far from being the only vegetable substances upon which acid, urinous, and alcalizate salts have the like operations to those recited in those two experiments. For ripe privet berries (for instance) being crushed upon white paper, though they stain it with a purplish colour, yet if we let fall on some part of it two or three drops of spirit of salt, and on the other part a little more of the strong solution of pot-ashes, the former liquor immediately turned that part of the thick juice or pulp, on which it fell, into a lovely red, and the latter turned the other part of it into a delightful green. Though I will not undertake, that those colours in that substance shall not be much more orient than lasting; and though (Pyrophilus) this experiment may seem to be almost the same with those already delivered concerning syrup of violets, and the juice of blue-bottles, yet I think it not amiss to take occasion to inform you, that this experiment reaches much farther than perhaps you yet imagine, and may be of good use to those, whom it concerns to know how dying stuffs may be wrought upon by saline liquors. For, I have found this experiment to succeed in so many various berries, flowers, blossoms, and other finer parts of vegetables, that neither my memory, nor my leisure serves me to enumerate them. And it is somewhat surprizing to see, by how differingly-coloured flowers, or blossoms, (for example) the paper being stained, will by an acid spirit be immediately turned red, and by any alcaly or any urinous spirit turned green; insomuch that even the crushed blossoms of meserion, (which I gathered in winter and frosty weather) and those of peas, crushed upon white paper, how remote soever their colours be from green, would in a moment pass; into a deep degree of that colour, upon the touch of an alcalizate liquor. To which let us add, that either of those new pigments (if I may so call them) may, by the affusion of enough of a contrary liquor, be presently changed from red into green, and from green into red: which observation will hold also in syrup of violets, juices of blue-bottles, &c.

AFTER what I have formerly delivered to evince that there are many instances, wherein new colours are produced or acquired by bodies, which chymists are wont to think destitute of salt, or to whose change of colours no new accession of saline particles does appear to contribute; I think we may safely enough acknowledge, that we have taken notice of so many changes made by the intervention of salts in the colours of mixed bodies, that it has lessened our wonder, that though many chymists are wont to ascribe the colours of such bodies to their sulphureous, and the rest to their mercurial principle; yet Paracesus himself directs us in the indagation of colours, to have an eye principally upon salts, as we find in that passage of his, wherein he takes upon him to oblige his readers much by instructing them, of what things they are to expect the knowledge from each of the three distinct principles of bodies. Alias (says he) colorum similis ratio est: de quibus brevem institutionem banc attendite, quod scilicet colores omnes ex sale prodeant. Sal enim dat colorem, dat balsamum. And a little beneath; Fam natura ipsa colores protrahit ex sale, cuique speciei dans i11um, qui ipsi competit, &c. After which he concludes; Itaque qui rerum omnium corpora cognoscere, vult, huic opus est, ut ante omnia cognoscat sulphur; ab boc, qui desiderat novisse colores, is scientiam istorum petat a sale; qui scire vult virtutes, is scruteturer arcana Mercurii. Sic nimirum fundamentum hauserit mysteriorum, in quolibet crescenti indagandorum, prout natura cuilibet specie ea ingessit. But though Paracesus ascribes to each of his beloved hypostatical principles much more than I fear will be found to belong to it; yet if we please to consider colours, not as philosophers, but as dyers, the concurrence of salts to the striking and change of colours, and their efficacy, will, I suppose, appear so considerable, that we shall not need to quarrel much with Paracesus, for ascribing in this place (for I dare not affirm that he uses to be still of one mind) the colours of bodies to their salts, if by salts he here understood not only elementary salts, but such also as are commonly taken for salts, as allom, crystals of tartar, vitriol, &c. because the saline principle does chiefly abound in them, though indeed they be, as we elsewhere declare, mixed bodies, and have most of them, besides what is saline, both sulphureous, aqueous, and gross or earthy parts.

BUT though (Pyrophilus) I have observed a red and green to be produced, the former, by acid salts, the latter by salts not acid, in the exprest juices of so many differing vegetable substances, that the observation, if pursued, may prove (as I said) of good use: yet to show you how much even these effects depend upon the particular texture of bodies, I must subjoin some cases wherein I (who am somewhat backwards to admit observations for universal) had the curiosity to discover, that the experiments would not uniformly succeed; and of these exceptions, the chief that I now remember, are reducible to the following three.

And (first) I thought fit to try the operation of acid salts upon vegetable substances, that are already and by their own nature red. And accordingly I made trial upon syrup of clove-julyflowers, the clear expressed juice of the succulent berries of Spina Cervina or buckthorn, (which I had long kept by me for the sake of its deep colour) upon red roses, infusion of Brazil, and divers other vegetable substances, on some of which crushed (as is often mentioned) upon white paper (which is also to be understood in most of these experiments, if no circumstance of them argue otherwise) spirit of salt either made no considerable change, or altered the colour but from a darker to a lighter red. How it will succeed in many other vegetable juices, and infusions of the same colour, I have at present so few at hand, that I must leave you to find it out yourself. But as for the operation of the other sort of salts upon these red substances, I found it not very uniform, some red, or reddish infusions, as of roses, being turned thereby into a dirty colour, but yet inclining to green. Nor was the syrup of clove-julyflowers turned by the solution of pot-ashes to a much better, though somewhat a greener colour. Another sort of red infusions was by an alcaly not turned into a green, but advanced into a crimson, as I shall have occasion to note ere long. But there were other sorts, as particularly the lovely coloured juice of buckthorn berries, that readily passed into a lovely green,

AMONG other vegetables, which we thought likely to afford exceptions to the general observation about the differing changes of colours produced by acid and sulphureous salts, we thought fit to make trial upon the flowers of jasmin, they being both white as to colour, and esteemed to be of a more oily nature than other flowers. Whereupon having taken the white parts only of the flowers, and rubbed them somewhat hard with my finger, upon a piece of clean paper, it appeared very little discoloured. Nor had spirit of salt, wherewith I moistened one part of it, any considerable operation upon it. But spirit of urine, and somewhat more effectually a strong alcalizate solution, did immediately turn the almost colourless paper moistened by the juice of the jasmin, not as those liquors are wont to do, when put upon the juices of other flowers, of a good green, but of a deep, though somewhat greenish yellow; which experiment I did afterwards at several times repeat with the like success. But it seems not that a great degree of unctuousness is necessary to the production of the like effects, for when we tried the experiment with the leaves of those purely white flowers that appear about the end of winter, commonly called snow-drops, the event was not much unlike that, which we have been newly mentioning.

ANOTHER sort of instances to show how much changes of colours, effected by salts, depend upon the particular texture of the coloured bodies, has been afforded me by several yellow flowers, and other vegetables, as marygold leaves, early primroses, fresh madder, &c. For being rubbed upon white paper, till they imbued it with their colour, I found not, that by the addition of alcalizate liquors, nor yet by that of an urinous spirits they would be turned either green or red: nor did so acid a spirit as that of salt considerably alter their colour, save that it seemed a little to dilute it: only in some early primroses it destroyed the greatest part of the colour, and made the paper almost white again. And madder also afforded something peculiar, and very differing from what we have newly mentioned: for having gathered some roots of it, and (whilst they were recent) expressed upon white paper, the yellow juice, an alcalizate solution dropt upon it did not turn it either green or white, but red. And the bruised madder itself being drenched with the like alcalizate solution, exchanged also its yellowness for a redness.

HAVING thus (Pyrophilus) given you divers instances, to countenance the general observation delivered in the twenty-fifth experiment, and divers exceptions whereby it ought to be limited; I must leave the further inquiry into these matters to your own industry. For not remembering at present many of those other trials, long since made to satisfy myself about particulars, and not having now the opportunity to repeat them, I must content myself to have given you the hint, and the ways of prosecuting the search yourself and only declare to you in general, that, as I have made many trials, unmentioned in this treatise, whose events were agreeable to those mentioned in the twenty-fifth experiment, so (to name now no other instances) what I have tried with acid and sulphureous salts upon the pulp of juniper berries, rubbed upon white paper, inclines me to think, that among that vast multitude, and strange variety of plants that adorn the face of the earth, perhaps many other vegetables may be found, on which such menstruums may not have such operations, as upon the juice of violets, peas-blossoms, &c. no nor upon any of those three other sorts of vegetables, that I have taken notice of in the three foregoing experiments: it sufficiently appearing even by these, that the effects of a salt upon the of particular vegetables do very much depend upon their particular textures.

IT may be of some use towards the discovery of the nature of these changes, which the alimental juice receives in some vegetables, according to the differing degrees of their maturity, and according to the differing kinds of plants of the same denomination, to observe what operation acid, urinous, and alcalizate salts will have upon the juices of the several sorts of the vegetable substances I have been mentioning.

To declare my meaning by an example; I took from the same cluster one blackberry full ripe, and another that had not yet gone beyond a redness; and rubbing a piece of white paper with the former, I observed that the juice adhering to it was of a dark reddish colour, full of little black specks, and that this juice, by a drop of a strong lixivium, was immediately turned into a greenish colour deep enough; by as much urinous spirit, into a colour much of kin to the former, though somewhat differing, and fainter; and by a drop of spirit of salt, into a fine and lightsome red: whereas the red berry being in like manner rubbed upon paper, left on it a red colour, which was very little altered by the acid spirit newly named, and by the urinous and lixiviate salts received changes of colour, differing from those that had been just before produced in the dark juice of the ripe black berry.

I REMEMBER also that though the infusion of damask roses would as well, though not so much, as that of red, be heightened by acid spirits to an intense degree of redness, and by lixiviate salts be brought to a darkish green; yet having for trial's sake taken a rose, whose leaves, which were large and numerous, like those of a Provence rose, were perfectly yellow, though in a solution of salt of tartar, they afforded a green blueish tincture, yet I did not by an acid liquor obtain a red one; all that the saline spirit I employed performed, being (if I much mis-remember not) to dilute somewhat the yellowness of the leaves. I would also have tried the tincture of yellow violets, but could procure none. And if I were in those islands of Banda, which are made famous as well as rich, by being the almost only place where cloves will prosper, I should think it worth my curiosity to try, what operation the three differing kinds of salts, I have so often mentioned, would have upon the juice of this spice (expressed at the several seasons of it) as it grows upon the tree. Since good authors inform us (of what is remarkable) that these, whether fruits, or rudiments of fruits, are at first white, afterward green, and then reddish, before they be beaten off the tree; after which being dried before they are put tip, they grow blackish, as we see them. And one of the recentest Herbarists informs us, that the flower grows upon the top of the clove itself, consisting of four small leaves, like a cherry-blossom, but of an excellent blue. But (Pyrophilus) to return to our own observations, I shall add, that I the rather chuse to mention to you an example drawn from roses, because that though I am apt to think, as I elsewhere advertise, that something may be guessed at about some of the qualities of the juices of vegetables, by the resemblance or disparity that we meet with in the changes made of their colours, by the operation of the same kinds of salts; yet that those conjectures should be very warily made, may appear, among other things, by the instance I have chosen to give in roses. For though (as I formerly told you) the dried leaves, both of the damask, and of red ones, give a red tincture to water sharpened with acid salts, yet the one sort of leaves is known to have a purgative faculty, and the other are often, and divers ways employed for binding.

AND I also chuse (Pyrophilus) to subjoin this twenty-ninth experiment to those that precede it, about the change of the colours of vegetables by salts, for these two reasons: the first, that you may not easily entertain suspicions, if in the trials of an experiment of some of the kinds formerly mentioned, you should meet with an event somewhat differing from what my relations have made you expect. And the second, that you may hereby be invited to discern, that it may not be amiss to take notice of the particular seasons wherein you gather the vegetables which in nicer experiments you make use of. For, if I were not hindered both by haste and some justifiable considerations, I could perhaps add considerable instances; to those lately delivered, for the making out of this observation; but for certain reasons I shall at present substitute a remarkable passage to be met with in that laborious Herbarist Mr. Parkinson, where treating of the virtues of the (already divers times mentioned) buckthorn berries, he subjoins the following account of several pigments that are made of them, not only according to the several ways of handling them, but according to the differing seasons of maturity, at which they are gathered. Of these berries (says he) are made three several sorts of colours as they shall be gathered, that is, being gathered while they are green, and kept dry, are called sapberries, which being steeped into some allom-water, or fresh bruised into allom-water, they give a reasonable fair yellow colour which painters use for their work, and book binders to colour the edges of books, and leather-dressers to colour fleather; as they use also to make a green colour, called sap-green, taken from the berries when they are black, being bruised and put into a brass or copper kettle or pan, and there sufered to abide three or four days,or a little heated upon the fire, and some beaten allum put unto them, and afterwards pressed forth; the juice or liquor is usually put into great bladders tied with strong thread at the bead and hung up until it be dry, which is disssolved in water or wine, but sack (he affirms) is the best to preserve the colour from starving (as they call it) that is, from decaying, and make it hold fresh the longer. The third colour (whereof none, says he, that I can find have made mention but only Tragus) is a purplish colour, which is made of the berries suffered to grow until middle or end of November, that they are ready to drop from the trees.

AND, I remember (Pyrophilus) that I tried, with a success that pleased me well enough, to make such a kind of pigment, as the painters call sap-green, by a way not unlike that delivered here by our author, but I cannot now find any thing relating to that matter among my loose papers. And my trials were made so many years ago, that I dare not trust my memory for circumstances, but will rather tell you, that in a noted colour-shop I brought them by questions to confess to me, that they made their sap-green much after the ways by our Botanist here mentioned. And on this occasion I shall add an observation, which though it does not strictly belong to this place, may well enough be mentioned here; namely, that I find by an account given us by the learned Clusius, of alaternus, that even the grosser parts of the same plant are some of them one colour, and some another: for speaking of that plant, he tells us, that the Portugals use the bark to dye their nets into a red colour, and with the chips of the wood, which are whitish, they dye a blackish blue.

AMONG the experiments that tend to shew that the change of colours in bodies may proceed from the varied texture of their parts, and the consequent change of their disposition to reflect or refract the light, that sort of experiments must not be left unmentioned, which is afforded us by chymical digestions. For, if chymists will believe several famous writers about what they call the philosopher's stone, they must acknowledge that the same matter, sealed up hermetically in a philosophical egg, will, by the continuance of digestion, or if they will have it so (for it is not material in our case which of the two it be) of decoction, run through a great variety of differing colours, before it come to that of the noblest elixir; whether that be scarlet, or purple, or whatever other kind of red. But without building any thing on so abstruse and questionable an operation (which yet may be pertinently represented to those that believe the thing) we may observe, that divers bodies digested in carefully closed vessels, will in tract of time change their colour: as I have elsewhere mentioned my having observed even in rectified spirit of hartshorn, and as is evident in the precipitations of amalgams of gold and mercury, without addition, where, by the continuance of a due heat, the silver-coloured amalgam is reduced into a shining red powder. Further instances of this kind you may find here and there in divers places of my other essays. And indeed it has been a thing, that has much contributed to deceive many chymists, that there are more bodies than one, which by digestion will be brought to exhibit that variety and succession of colours, which they imagine to be peculiar to what they call the true matter of the philosophers. But concerning this, shall refer you to what you may elsewhere find in the discourse written touching the passive deceptions of chymists, and more about the production of colours by digestion you will meet with presently. Wherefore I shall now make only this observation from what has been delivered, that in these operations there appears not any cause to attribute the new colours emergent to the action of a new substantial form, nor to any increase or decrement of either the salt, sulphur, or mercury of the matter that acquires new colours: for the vessels are closed, and these principles, according to the chymists, are ingenerable and incorruptible; so that the effect seems to proceed from hence, that the heat agitating and shuffling the corpuscles of the body exposed to it, does in process of time so change its texture, as that the transposed parts do, modify the incident light otherwise than they did when the matter appeared of an other colour.

AMONG the several changes of colour, which bodies acquire or disclose by digestion, it is very remarkable, that chymists find a redness rather than any other colour in most of the tinctures they draw, and even in the more gross solutions they make of almost all concretes, that abound either with mineral or vegetable sulphur, though the menstruum employed about these solutions or tinctures be ever so limpid or colourless.

THIS we have observed in I know not how many tinctures drawn with spirit of wine from jalap, guaiacum, and several other vegetables, and not only in the solutions of amber, benzoin, and divers other concretes made with the same menstruum, but also in divers mineral tinctures. And, not to urge that familiar instance of the ruby of sulphur, as chymists upon the score of its colour call the solution of flowers of brimstone, made with the spirit of turpentine, nor to take notice of other more known examples of the aptness of chymical oils to produce a red colour with the sulphur they extract, or dissolve, not to insist (I say) upon instances of this nature, I shall further represent to you, as a thing remarkable, that both acid and alcalizate salts, though in most other cases of such contrary operations, in reference to colours, will, with many bodies that abound with sulphureous, or with oily parts, produce a red; as is manifest partly in the more vulgar instances of the tinctures, or solutions of sulphur made with lixiviums, either of calcinated tartar or pot-ashes, and other obvious examples, partly by this, that the true glass of antimony extracted with some acid spirits, with or without wine, will yield a red tincture, and that I know an acid liquor, which in a moment will turn oil of turpentine into a deep red. But among the many instances I could give you of the easy production of redness by the operation of saline spirit, as well as of spirit of wine; I remember two or three of those I have tried, which seem remarkable enough to deserve to be mentioned to you apart.

BUT before we set them down, it will not perhaps appear impertinent to premise,

THAT there seems to be a manifest disparity betwixt red liquors, so that some of them may be said to have a genuine redness in comparison of others, that have a yellowish redness: for if you take (for example) a good tincture of cochineal, dilute it ever so much with fair water, you will not (as far as I can judge by what I have tried) be able to make it a yellow liquor. Insomuch that a single drop of a rich solution of cochineal in spirit of urine, being diluted with above an ounce of fair water, exhibited no yellowishness at all, but a fair (though somewhat faint) pink or carnation; and even when cochineal was by degrees diluted much beyond the newly mentioned colour, by the way formerly related to you in the twenty fourth experiment, I remember not, that there appeared in the whole trial any yellow. But if you take balsam of sulphur (for instance) though it may appear in a glass, where it has a good thickness, to be of a deep red; yet if you shake the glass, or pour a few drops on a sheet of white paper, spreading them on it with your finger, the balsam that falls back along the sides of the glass, and that which stains the paper, will appear yellow, not red. And there are divers tinctures, such as that of amber made with spirit of wine (to name now no more) that will appear either yellow or red, according as the vessels that they fill are slender or broad.

BUT to proceed to the experiments I was about to deliver: first, oil or spirit of turpentine, though clear as fair water, being digested upon the purely white sugar of lead, has, in a short time, afforded us a high red tincture, that some artists are pleased to call the balsam of Saturn, which they very much (and probably not altogether without cause) extol as an excellent medicine in divers outward affections.

NEXT, take of common brimstone finely powdered five ounces, of sal-armoniac likewise pulverized an equal weight, of beaten quicklime six ounces, mix these powders exquisitely, and distil them through a retort placed in sand by degrees of fire, giving at length as intense a heat as you well can in sand; there will come over (if you have wrought well) a volatile tincture of sulphur, which may probably prove an excellent medicine, and should have been mentioned among the other preparations of sulphur, which we have elsewhere imparted to you, but that it is very pertinent to our present subject, the change of colours. For though none of the ingredients be red, the distilled liquor will be so: and this liquor, if it be well drawn, will, upon a little agitation of the phial first unstopped (especially if it be held in a warmer hand) send forth a copious fume, not red, like that of nitre, but white; and sometimes this liquor may be so drawn, that I remember, not long since, I took pleasure to observe in a parcel of it, that ingredients not red, did not only yield by distillation a volatile spirit that was red, but though that liquor did upon the bare opening of the bottle it was kept in, drive us away with the plenty and sulphureous scent of a white steam which it sent forth, yet the liquor itself being touched by our fingers, did immediately dye them black.

THE third and last experiment I shall now mention, to shew how prone bodies abounding in sulphureous parts are to afford a red colour, is one, wherein by the operation of a saline spirit upon a white or whitish body, which according to the chymists should be altogether sulphureous, a redness may be produced, not (as in the former experiments) slowly, but in the twinkling of an eye. We took then of the essential oil of aniseeds, which has this peculiarity, that in cold weather it loses its fluidity and the greatest part of its tranparancy, and looks like a white or whitish ointment, and near at hand seems to consist of a multitude of little soft scales: of this coagulated stuff was spread a little with a knife upon a piece of white paper, and letting all on it, and mixing with it, a drop or two of oil of vitriol, immediately (as we foresaw) there emerged together with some heat and smoke, a blood-red colour which therefore was in a trice produced by two bodies, whereof the one had but a whitish colour, and the other (if carefully rectified) had no colour at all.

BUT on this occasion (Pyrophilus) we must add once for all, that in many of of the above recited experiments, though the changes of colour happened as we have mentioned them I yet the emergent or produced colour is oft-times very subject to degenerate, both quickly and much. Notwithstanding which, since the changes, we have set down, do happen presently upon the operation of the bodies upon each other, or at the times by us specified that is sufficient both to justify our veracity, and to shew what we intend; it not being essential to the genuineness of a colour to be durable. For a fading leaf, that is ready to rot, and moulder into dust, may have as true a yellow, as a wedge of gold, which so obstinately resists both time and fire. And the reason why I take occasion from the former experiment to subjoin this general advertisement, is, that I have several times observed, that the mixture resulting from the oils of vitriol, and of aniseeds, though it acquire a thicker consistence than either of the ingredients had, has quickly lost its colour, turning in a very short time into a dirty grey, at least in the superficial parts, where it is exposed to the air: which last circumstance I therefore mention, because that, though it seem probable, that this degeneration of colours may oft-times and in divers cases proceed from the further action of the saline corpuscles, and the other ingredients upon one another, yet in many cases much of the quick change of colours seems ascribeable to the air, as may be made probable by several reasons; the first whereof may be fetched from the newly recited example of the two oils; the next may be, that we have sometimes observed long window-curtains of light colours to have that part of them, which was exposed to the air, when the window was open of one colour, and the lower part, that was sheltered from the air by the wall, of another colour: and the third argument may be fetched from divers observations, both of others, and our own; for of that pigment so well known in painters shops, by the name of Turnsol, our industrious Parkinson, in the particular account he gives of the plant that bears it, tells us also, That the berries, when they are at their full maturity, have within them between the skin and the inward kernel or seed, a certain juice or moisture, which being rubbed upon paper or cloth, at the first appears of a fresh and lovely green colour, but presently changeth into a kind of blueish purple, upon the cloth or paper; and the same cloth afterwards wet in water, and wrung forth, will colour the water into a claret-wine colour; and these (concludes he) are those rags of cloth, which are usually called turnsol in the druggists or grocers shops. And to this observation of our Botanist we will add an experiment of our own (made before we met with that) which, though in many circumstances very differing, serves to prove the same thing. For having taken of the deeply red juice of buckthorn berries, which I bought of the man that uses to fell it to the apothecaries, to make their syrup de spina cervina, I let some of it drop upon a piece of white paper, and having left it there for many hours, till the paper was grown dry again, I found what I was inclined to suspect, namely, that this juice was degenerated from a deep red to a dirty kind of greyish colour, which, in a great part of the stained paper, seemed not to have to much as an eye of red: though a little spirit of salt or dissolved alcali would turn this unpleasant colour (as formerly I told you it would change the not yet altered juice) into a red or green. And to satisfy myself, that this degeneration of colour did not proceed from the paper, I dropped some of the deep red or crimson juice upon a white glazed tile, and suffering it to dry on there, I found that even in that body, on which it could not soak, and by which it could not be wrought, it nevertheless lost its colour. And these instances (Pyrophilus) I am the more careful to mention to you, that you may not be much surprised or discouraged if you should sometimes miss of performing punctually what I affirm myself to have done in point of changing colours; since in these experiments the over-sight or neglect of such little circumstances, as in many others would not be perhaps considerable, may occasion the miscarrying of a trial. And I was willing also to take this occasion of advertising you in the repeating of the experiments mentioned in the treatise, to make use of the juices of vegetables, and other things prepared for your trials, as soon as ever they are ready, left one or other of them grow less fit, it not quite unfit by delay; and to estimate the event of trials by the change, that is produced presently upon the due and sufficient application of actives to passives (as they speak) because in many cases the effects of such mixtures may not be lasting, and the newly produced colour may in a little time degenerate. But (Pyrophilus) I forgot to add to the former observations lately made about vegetables, a third of the same import, made in mineral substances, by telling you, that the better to satisfy a friend or two in this particular, I sometimes made, according to some conjectures of mine, this experiment; that having dissolved good silver in aqua fortis, and precipitated it with spirit of salt, upon the first decanting of the liquor, the remaining matter would be purely white; but after it had lain a while uncovered, that part of it that was contiguous to the air, would not only lose its whiteness, but appear of a very dark and almost blackish colour; I say, that part that was contiguous to the air, because if that were gently taken off, the subjacent part of the same mass would appear very white, till, that also, having continued a while exposed to the air, would likewise degenerate. Now whether the air performs these things by the means of a subtile salt, which we elsewhere shew it not to be destitute of, or by a piercing moisture, that is apt easily to insinuate itself into the pores of some bodies, and thereby change their texture, and so their colour; or by soliciting the avolation of certain parts of the bodies, to which it is contiguous; or by some other way (which possibly I may elsewhere propose and consider) I have not now the leisure to discourse. And for the same reason, though I could add many other instances, of what I formerly noted touching the emergency of redness upon the digestion of many bodies, insomuch that I have often seen upon the borders of France (and probably we may have the like in England) a sort of pears, which digested for some time with a little wine, in a vessel exactly closed, will in not many hours appear throughout of a deep red colour (as, also that of the juice, wherein they are stewed, becomes) but even on pure and white salt of tartar, pure spirit of wine, as clear as rock-water, will (as we elsewhere declare) by long digestion acquire a redness: though I say such instances might be multiplied, and though there be some other obvious changes of colours, which happen so frequently, that they cannot but be as well considerable as notorious; such as is the blackness of almost all bodies burned in the open air; yet our haste invites us to resign you the exercise of inquiring into the causes of these changes. And certainly, the reason both why the soots of such differing bodies are almost all of them all black, why so much the greater part of vegetables should be rather green than of any other colour, and particularly (which more directly concerns the place) why gentle heats do so frequently in chymical operations produce rather a redness than any other colour in digested menstruums, not only sulphureous, as spirit of wine, but saline, as spirit of vinegar, may be very well worth a serious enquiry which I shall therefore recommend to Pyrophilus and his ingenious friends.

IT may seem somewhat strange, that if you take the crimson solution of cochineal, or the juice of black cherries, and of some other vegetables that afford the like colour (which because many take but for a deep red, we do with them sometimes call it so) and let some of it fall upon a piece of paper, a drop or two of an acid spirit, such as spirit of salt, or aqua fortis, will immediately turn it into a fair red. Whereas, if you make an infusion of brazil in fair water, and drop a little spirit of salt or aqua fortis into it, that will destroy its redness, and leave the liquor of a yellow (sometimes pale) I might perhaps plausibly enough say on this occasion, that if we consider the case a little more attentively, we may take notice, that the action of the acid spirit seems in both cases but to weaken the colour of the liquor on which it falls. And so though it destroy redness in the tincture of brazil, as well as produce red in the tincture of cochineal, its operations may be uniform enough, since as crimson seems to be little else than a very deep red, with (perhaps) an eye of blue, so some kinds of red seem (as I have lately noted) to be little else than heightened yellow. And subsequently in such bodies, the yellow seems to be but a diluted red. And accordingly alcalizate solutions and urinous spirits, which seem disposed to deepen the colours of the juices and liquors of most vegetables, will not only restore the solution of cochineal and the infusion of brazil to crimson, whence the spirit of salt had changed them into a truer red; but will also (as I lately told you) not only heighten the yellow juice of madder into red, but advance the red infusion of brazil to a crimson. But I know not whether it will not be much safer to derive these changes from varied textures, than certain kinds of bodies; and you will perhaps think it worth while, that I should add on this occasion, that it may deserve some speculation, why, notwithstanding what we have been observing, though blue and purple seem to be deeper colours; than red, and therefore the juices of plants of either of the two former colours may (congruously enough to what has been just now noted) be turned red by spirit of salt or aqua fortis, yet blue syrup of violets and some purples should both by oil of tartar and spirit of urine be changed into green, which seems to be not a deeper, but a more diluted colour than blue, if not also than purple.

IT would much contribute to the history of colours, if chymists would in their laboratories take a heedful notice, and give us a faithful account of the colours observed in the steams of bodies either sublimed or distilled, and of the colours of those productions of the fire, that are made up by the coalition of those steams. As (for instance) we observe in the distilling of pure salt-petre, that at a certain season of the operation, the body, though it seem either crystalline, or white, affords very red fumes: whereas though vitriol be green or blue, the spirit of it is observed to come over in whitish fumes. The like colour I have taken notice of in the fumes of several other concretes of differing colours, and natures, especially when distil1ed with strong fires. And we elsewhere note, that even soot, as black as it is, has filled our receivers with such copious white fumes, that they seemed to have had their insides washed with milk. And no less observable may be the distilled liquors, into which such fumes convene (for though we will not deny, that by skill and care a reddish liquor may be obtained from nitre) yet the common spirit of it, in the making even of which, store of these red fumes are wont to pass over into the receiver, appears not to be at all red. And besides, that neither the spirit of vitriol, nor that of soot is any thing white; and, besides also, that as far as I have observed, most (for I say not all) of the empyreumatical oils of wood, and other concretes, are either of a deep red, or of a colour between red and black; besides this, I say, it is very remarkable, that notwithstanding that great variety of colours to be met with in the herbs, flowers, and other bodies wont to be distilled in balneo; yet (as far at least as our common distillers experience reacheth) all the waters and spirits that first come over by that way of distillation, leave the colours of their concretes behind them, though indeed there be one or two vegetables not commonly taken notice of, whose distilled liquors I elsewhere observe to carry over the tincture of the concrete with them. And as in distillations, so in sublimations, it were worth while to take notice of what comes up, in reference to our present scope, but purposely performing them (as I have in some cases done) in conveniently shaped glasses, that the colour of the ascending fumes may be discerned; for it may afford a Naturalist good information to observe the congruities or the differences betwixt the colours of the ascending fumes, and those of the flowers they compose by their convention. For it is evident, that these flowers do many of them, in point of colour, much differ, not only from one another, but ofttimes from the concretes that afforded them. Thus (not here to repeat what I formerly noted of the black soots of very differingly coloured bodies) though camphire and brimstone afford flowers much of their own colour, save that those of brimstone are wont to be a little paler, than the lumps that yielded them; yet even of red benzoin, that slublimed substance, which chymists call its flowers, is wont to be white or whitish. And to omit other instances, even one and the same black mineral, antimony, may be made to afford flowers, some of them red, and some grey, and, which is more strange, some of them purely white. And it is the prescription of some glass-men by exquisitely mingling a convenient proportion of brimstone, sal armoniac, and quicksilver, and subliming them together, to make a sublimate of an excellent blue; and though having caused the experiment to be made, we found the produced sublimate to be far from being of a lovely colour (as was promised) that here and there it seemed blueish, and at least was of a colour differing enough from either of the ingredients, which is sufficient for our present purpose. But a much finer colour is promised by some of the empirics, that pretend to secrets, who tell us, that orpiment being sublimed, will afford among the parts of it that fly upward, some little masses, which, though the mineral itself be of a good yellow, will be red enough to emulate rubies, both in colour and translucency. And this experiment may, or aught I know, sometimes succeed; for I remember, that having in a small bolt-head purposely sublimed some powdered orpirnent, we could in the lower part of the sublimite discern here and there some reddish lines, though much of the upper part of the sublimate consisted of a matter, which was not alone purely yellow, but transparent almost like a powder. And we have also this way obtained a sublimate, the lower part whereof though it consisted not of rubies, yet the small pieces of it, which were numerous enough, were of a pleasant reddish colour, and glistened very prettily. But to insist on such kind of trials and observations (where the ascending fumes of bodies differ in colour from the bodies themselves) though it might indeed enrich the history of colours, would rob me of too much of the little time I have to dispatch what I have further to tell you concerning them.

TAKE the dried buds (or blossoms) of the pomegranate tree (which are commonly called in the shops Balaustimus;) pull off the reddish leaves, and by a gentle ebullition of them in fair water, or by a competent infusion of them in like water well heated, extract a faint reddish tincture; which, if the liquor be turbid, you may clarify it by filtrating it. Into this, if you pour a little good spirit of urine, or some other spirit abounding in the like sort of volatile salts, the mixture will presently turn of a darkish green colour; but if instead of the forementioned liquor, you drop into the simple infusion a little rectified spirit of sea salt, the pale and almost colourless liquor will immediately not only grow more transparent, but acquire a high redness, like that of rich claret wine, which so suddenly acquired colour may as quickly be destroyed, and turned into a dirty blueish green, by the affusion of a competent quantity of the abovementioned spirit of urine.

THIS experiment may bring some light to, and receive some from a couple of other experiments, that I remember I have met with in the ingenious Gassendus's animadversions upon Epicurus's philosophy, whilst I was turning over the leaves of those learned commentaries, (my eyes being too weak to let me read such voluminous books quite through) and I the less scruple (nowithstanding my contrary custom in this treatise) to set down these experiments of another, because I shall a little improve the latter of them, and because by comparing therewith that which I have last cited, we may be assisted to conjecture upon what account it is, that oil of vitriol heightens the tincture of red rose leaves, since spirit of salt, which is a highly acid menstruuum, but otherwise differing enough from oil of vitriol, does the same thing. Our author's experiments then, as we made them, are these: We took about a glass-full of lukewarm water, and in it immerged a quantity of the leaves of senna, and presently upon the immersion there did not appear any redness in the water but dropping into it a little oil of tartar, the liquor soon discovered a redness, to the watchful eye; whereas by a little of that acid liquor of vitriol, which is like the former undeservedly called oil, such a colour would not be extracted from the infused henna. On the other side, we took some red-rose leaves dried, and having shaken them into a glass of fair water, they imparted to it no redness but upon the affusion of a little oil of vitriol the water was immediately turned red, which it would not have been, if instead of oil of vitriol, we had employed oil of tartar to produce that colour. That these were Gassendus his experiments, I partly remember, and was assured by a friend, who lately transcribed them out of Gassendus his book, which, I therefore add, because I have not now that book at hand. And the design of Gassendus in these experiments our friend affirms to be, to prove, that of things not red a redness may be made only by mixture, and the varied position of parts, wherein the doctrine of that subtile philosopher doth not a little authorize what we have formerly delivered concerning the emergency and change of colours. But the instances, that we have out of him set down, seem not to be the most eminent, that may be produced of this truth: for our next experiment will shew the production of several colours out of liquors, which have not any of them any such colour, nor indeed any discernable one at all. And whereas though our author tells us, that them, was no redness either in the water, or the leaves of senna, or the oil of tartar I and though it be true, that the predominant colour of the leaves of senna be another than red, yet we have tried, that by steeping that plant a night even in cold water, it would afford a very deep yellow or reddish tincture without the help of the oil of tartar, which seems to do little more than assist the water to extract more nimbly a plenty of that red tincture, wherewith the leaves of senna, do of themselves abound, and having taken off the tincture of senna, made only with fair water, before it grew to be reddish, and decanted it from the leaves, we could not perceive, that by dropping some oil, of tartar into it, that colour was considerable, though it were a little heightened into a redness, which might have been expected, if the particles of the oil did eminently co-operate, otherwise than we have expressed, to the production of this redness.

AND as for the experiment with red-rose leaves, the same thing may be alledged; for we found that such leaves, by bare infusion for a night and day in fair water, did afford us a tincture bordering at least upon redness, and that colour being conspicuous in the leaves themselves, would not by some seem so much to be produced as to be extracted by the affusion of oil of vitriol. And the experiment tried with the dry leaves of damask roses succeeded but imperfectly, but that is indeed observable to our author's pupose, that oil of tartar will not perform in this experiment what oil of vitriol doth: but because this last named liquor is not so easily to be had, give me leave to advertise you, that the experiment will succeed, if instead of it you employ aqua fortis. And though some trials of our own formerly made, and others easily deducible from what we have already delivered, about the different families and operations of salt, might enable us to present you an experiment upon red-rose leaves, more accommodated to our author's purpose than that which he hath given us; yet our reverence to so candid a philosopher, invites us rather to improve his experiment, than substitute another in its place. Take therefore of the tincture of red-rose leaves, (for with damask-rose leaves the experiment succeedeth not well) made as before hath been taught with a little oil of vitriol, and a good quantity of fair water; pour off this liquor into a clear phial half filled with limpid water, till the water held against the light have acquired a competent redness, without losing its transparency; into this tincture drop leisurely a little good spirit of urine, and shaking the phial, which you must still hold against the light, you shall see the red liquor immediately turned into a fine greenish blue, which colour was not to be found in any of the bodies, upon whose mixture re-emerged: and this change is the more observable, because in many bodies the degenerating of blue into red, is usual enough, but the turning of red into blue is very unfrequent. If at every drop of spirit of urine you shake the vial containing the red tincture, you may delightfully observe a pretty variety of colours in the passage of that tincture from a red to a blue, and sometimes we have this way hit upon such a liquor, as being looked upon against and from the light, did seem faintly to emulate the abovementioned tincture of Lignum Nephriticum. And if you make the tincture of red-roses very high, and, without diluting it with fair water, pour on the spirit of urine, you may have a blue so deep as to make the liquor opacous; but being dropt upon white paper, the colour will soon disclose itself. Also having made the red, and consequently the blue tincture very transparent, and suffered it to rest in a small open phial for a day or two, we found, according to our conjecture, that not only the blue but the red colour also vanished; the clear liquor being of a bright amber colour, at the bottom of which subsided a light, but copious feculency of almost the same colour, which seems to be nothing but the tincted parts of the rose-leaves drawn out by the acid spirits of the oil of vitriol, and precipitated by the volatile salt of the spirit of urine: which makes it the more probable, that the redness drawn by the oil of vitriol, was at least as well an extraction of the tinging parts of the roses, as a production of redness. And lastly, if you be destitute of spirit of urine, you may change the colour of the tincture of roses with many other sulphureous salts, as a strong solution of pot-ashes, oil of tartar, &c. which yet are seldom so free from feculency, as the spirituous parts of urine become by repeated distillation.

ON this occasion, I call to mind, that I found a way of producing, though not the same kind of blue, as I have been mentioning, yet a colour near of kin to it, namely, a fair purple, by employing a liquor not made red by art, instead of the tincture of red-roses made with an acid spirit: and my way was, only to take logwood (a wood very well known to dyers) having by infusing the powder of it a while in fair water made that liquor red, I dropt into it a tantillum of an urinous spirit, as that of sal armoniac (and I have done the same thing with an alcali) by which the colour was in a moment turned into a rich, and lovely purple. But care must be had, that you let not fall into a spoonful above two or three drops, lest the colour become so deep, as to make the liquor too opacous. And (to answer the other part of Gassetndus his experiment) if, instead of fair water, I infused the logwood in water made somewhat sour by the acid spirit of salt, I should obtain neither a purple liquor, nor a red, but only a yellow one.

THE experiment I am now to mention to you, Pyrophilus, is that which both you, and all the other Virtuosi that have seen it, have been pleased to think very strange; and indeed of all the experiments of colours I have yet met with, it seems to be the fittest to recommend the doctrine proposed in this treatise, and to shew that we need not suppose, that all colours must necessarily be inherent qualities, flowing from the substantial forms of the bodies they are said to belong to, since by a bare mechanical change of texture in the minute parts of bodies, two colours may in a moment be generated quite de novo, and utterly destroyed. For there is this difference betwixt the following experiment, and most of the others delivered in these papers, that in this, the colour that the body already had, is not changed into another, but betwixt two bodies, each of them apart devoid of colour, there is in a moment generated a very deep colour, and which, if it were let alone, would be permanent; and yet by a very small parcel of a third body, that has no colour of its own (lest some may pretend I know not what antipathy betwixt colours) this otherwise permanent colour will be in another trice so quite destroyed, that there will remain no footsteps either of it or of any other colour in the whole mixture.

THE experiment is very easy, and it is thus performed: take good common sublimate, and fully satiate with it what quantity of water you please, filtre the solution carefully through clean and close paper, that it may drop down as clear and colourless as fountain water. Then, when you'll shew the experiment, put of it about a spoonful into a small wine-glass, or any other convenient vessel made of clear glass, and dropping in three or four drops of good oil of tartar per deliquium, well filtred, that it may likewise be without colour: these two limpid liquors will in the twinkling of an eye turn into an opacous mixture of a deep orange colour, which by keeping the glass continually shaking in your hand, you must preserve from settling too soon to the bottom; and when the spectators have a little beheld this first change, then you must presently drop in about four or five drops of the oil of vitriol, and continuing to shake the glass pretty strongly, that it may the nimbler diffuse itself, the whole colour, if you have gone skilfully to work, will immediately disappear, and all the liquor in the glass will be clear and colourless as before, without so much as a sediment at the bottom. But for the more graceful trial of this experiment, it will not be amiss to observe, first, that there should not be taken too much of the solution of sublimate, nor too much of the oil of tartar dropped in, to avoid the necessity of putting in so much oil of vitriol as may make an ebullition, and perhaps run over the glass. Secondly, that it is convenient to keep the glass always a little shaking, both for the better mixing of the liquors, and to keep the yellow substance from subsiding, which else it would in a short time do; though when it is subsided it will retain its colour, and also be capable of being deprived of it by the oil newly mentioned. Thirdly, that if any yellow matter stick at the sides of the glass, it is but inclining the glass, till the clarified liquor can wash along it, and the liquor will presently imbibe it, and deprive it of its colour.

MANY have sometimes wondered, how I came to light upon this experiment; but the notions or conjectures I have about the differing natures of the several tribes of salts, having led me to devise the experiment, it will not be difficult for me to give you the chymical reason, if I may so speak, of the phenomenon. Having then observed, that mercury, being dissolved in some menstruums, would yield a dark yellow precipitate, and supposing that, as to this, common water, and the salts that stick to the mercury would be equivalent to those acid menstruums, which work upon the quicksilver, upon the account of their saline particles, I substituted a solution of sublimate in fair water, instead of a solution of mercury in aqua fortis, or spirit of nitre, that simple solution being both clearer and free from that very offensive smell, which accompanies the solutions of mercury made with those other corrosive liquors. Then I considered, that that which makes the yellow colour is indeed but a precipitate made by the means of the oil of tartar, which we drop in, and which, as the chymists know, does generally precipitate metalline bodies corroded by acid salts: so that the colour in our case results from the coalition of the mercurial particles with the saline ones, wherewith they were formerly associated, and with the alcalizate particles of the salt of tartar that swim up and down in the oil. Wherefore considering also, that very many of the effects of lixiviate liquors, upon the solutions of other bodies, may be destroyed by acid menstruums, as I elsewhere more particularly declare, I concluded, that if I chose a very potently acid liquor, which by its incisive power might undo the work of the oil of tartar, and disperse again those particles, which the other had by precipitation associated, into such minute corpuscles as were before singly inconspicuous, they would become inconspicuous again, and consquently leave the liquor as colourless as before the precipitation was made.

THIS as I said, Pyrophilus, seems to be the chymical reason of this experiment; that is, such a reason, as, supposing the truth of those chymical notions I have elsewhere I hope evinced, may give such an account of the phænomena as chymical notions can supply us with: but I both here and elsewhere make use of this way of speaking, to intimate that I am sufficiently aware of the difference betwixt a chymical explication of a phenomenon, and one that is truly philosophical or mechanical; as in our present case, I tell you something, when I tell you that the yellowness of the mercurial solution, and the oil of tartar, is produced by the precipitation occasioned by the affusion of the latter of those liquors, and that the destruction of the colour proceeds from the dissipation of that curdled matter, whose texture is destroyed, and which is dissolved into minute and invisible particles by the potently acid menstruum: which is the reason, why there remains no sediment in the bottom, because the infused oil takes it up, and resolves it into hidden or invisible parts, as water does salt or sugar. But when I have told you all this, I am far from thinking I have told all that such an inquisitive person as yourself would know. for I presume you would desire, as well as I, to learn (at least) why the particles of the mercury, of the tartar, and of the acid salts convening together, should make rather an orange colour than a red, or a blue, or a green. For it is not enough to say what I related a little before, that divers mercurial solutions, though otherwise made, would yield a yellow precipitate, because the question will recur concerning them; and to give it a satisfactory answer, is, I freely acknowledge, more than I dare as yet pretend to.

BUT to confirm my conjecture about the chymical reason of our experiment, I may add, that as I have (viz. pag. 11. of this treatise) elsewhere (on another occasion) told you, with saline liquors of another kind and nature than salt of tartar (namely, with spirit of urine, and liquors of kin to that) I can make the mercury precipitate out of the first simple solution quite of another colour than that hitherto mentioned; nay, if instead of altering the precipitating liquor, I altered the texture of the sublimate in such a way as my notions about salt required, I could produce the same phenomenon. For having purposely sublimed together equal parts (or thereabout) of sal armoniac and sublimate, first diligently mixed, the ascending flowers being dissolved in fair water, and filtred, gave a solution limpid and colourless, like that of the other sublimates, and yet an alcaly dropped into this liquor did not turn it yellow but white. And upon the same grounds we may with quicksilver, without the help of common sublimate, prepare another sort of flowers dissolube in water without discolouring it, with which I could likewise do what I newly mentioned; to which I shall add (what possibly you will somewhat wonder at) that so much does the colour depend upon the texture resulting from the convention of the several sorts of corpuscles, that though, in our experiment, oil of vitriol destroys the yellow colour, yet with quicksilver And fair water, by the help of oil of vitriol alone, we may easily make a kind of precipitate of a fair and permanent yellow, as you will ere long (in the forty-second experiment of this third part) be taught. And I may further add, that I chose oil of vitriol, not so much for any other or peculiar quality, as for its being, when it is well rectified (which it is somewhat hazardous to bring it to be) not only devoid of colour and ill smells, but extremely strong and incisive. For though common and undephlegmated aqua fortis will not perform the same thing well, yet that which is made exceeding strong, by being carefully dephlegmed, will do it pretty well, though not so well as oil of vitriol; which is so strong, that even without rectification it may for a need be made use of. I will not here tell you what I have tried, that I may be able to deprive at pleasure the precipitate that one of the sulphureous liquors had made, by the copious affusion of the other; because I found, though this experiment is too ticklish to let me give a full account of it in few words, I shall therefore tell you, that it is not only for once, that the other above-mentioned experiment may be made, the same numerical parcels of liquor being still employed in it. For after I have clarified the orange-coloured liquor, by the addition of as little of the oil of vitriol as will suffice to perform the effect, I can again at pleasure reproduce the opacous colour, by the dropping in of fresh oil of tartar, and deltroy it again by the re-affusion of more of the acid menstruum; and yet oftener, if. I please, can I with these two contrariant liquors recall and disperse the colour, though by reason of the addition of so much new liquor, in reference to the mercurial particles, the colour will at length appear more dilute and faint.

AND, Pyrophilus, to confirm yet further the notions that led me to think on the proposed experiment, I shall acquaint you with another; which, when I had conveniency, I have sometimes added to it, and which has to the spectators appeared little less odd than the first. And though because the liquor, requisite to make the trial succeed well, must be on purpose prepared anew a while before, because it will not long retain its fitness for this work, I do but seldom annex this experiment to the other; yet I shall tell you how I devised it, and how I make it. If you boil crude antimony in a strong and clear lixivium, you shall separate a substance from it, which some modem chymists are pleased to call its sulphur, but how deservedly I shall not here examine, having elsewhere done it in an opportune place; wherefore I shall now but need to take notice, that when this supposed sulphur (not now to call it rather a kind of crocus) is let fall by the liquor upon its refrigeration, it often settles in flakes, or such-like parcels of a yellow substance (which being by the precedent dissolution reduced into minute parts, may peradventure be made to take fire much more easily than the grosser powder of unprepared antimony would have done.) Considering therefore, that common sulphur boiled in a lixivium, may be precipitated out of it by rhenish-wine or white-wine, which are sourish liquors, and have, in them, as I elsewhere shew, an acid salt; and having found also by trial, that with other acid liquors I could precipitate out of lixiviate solvents some other mineral concretions abounding with sulphureous parts, of which sort is crude antimony I concluded it to be easy to precipitate the antimony dissolved, as was lately mentioned, with the acid oil of vitriol. And though common sulphur yields a white precipitate, which the chymists call lac sulphuris, yet I supposed the precipitated antimony would be of a deep yellow colour, as well if made with oil of vitriol, as if made only by refrigeration and length of time. From this it was easy to deduce this experiment, that if you put into one glass some of the freshly impregnated and filtrated solution of antimony, and into another some of the orange-coloured mixture (which I formerly shewed you how to make with a mercurial solution and oil of tartar) a few drops of oil of vitriol dropped into the last mentioned glass would, as I told you before, turn the deep yellow mixture into a clear liquor; whereas a little of the same oil dropped out of the same phial into the other glass, would presently (but not without some ill scent) turn the moderately clear solution into a deep yellow substance. But this, as I said, succeeds not well, unless you employ a lixivium that has but newly dissolved antimony, and has not yet let it fall. But yet in summer-time, if your lixivium have been duly impregnated and well filtred after it is quite cold, it will for some days (perhaps much longer than I had occasion to try) retain antimony enough to exhibit, upon the affusion of the corrosive oil, as much of a good yellow substance as is necessary to satisfy the beholders of the possibility of the experiment.

THE knowledge of the distinction of salts which we have proposed, whereby they are discriminated into acid, volatile, or salfuginous (if I may for distinction sake so call the fugitive salts of animal substances) and fixed or alcalizate, may possibly (by that little part which we have already delivered, of what we could say of its applicableness) appear of so much use in natural philosophy (especially in the practic part of it) that I doubt not but it will be no unwelcome corollary of the preceding experiment, if by the help of it I teach you to distinguish which of those salts is predominant in chymical liquors, as well as whether any of them be so or not. For though in our notes upon the tenth and twentieth experiments I have shown you a way, by means of the tincture of Lignum Nephriticum, or of syrup of violets, to discover whether a propounded salt be acid or not; yet you can thereby only find in general that such and such salts belong not to the tribe of acids, but cannot determine whether they belong to the tribe of urinous salts (under which, for distinction sake, I comprehend all those volatile salts of animal or other substances that are contrary to acids) or to that of alcalies. For as well the one as the other of these salino-sulphureous salts will restore the ceruleous colour to the tincture of Lignum Nephriticum, and turn that of syrup of violets into green. Wherefore this XLth experiment does opportunely supply the deficiency of those. For being solicitous to find out some ready ways of discriminating the tribes of chymical salts, I found that all those I thought fit to make trial of, would, if they were of a lixiviate nature, make with sublimate dissolved in fair water an orange tawny precipitate; whereas, if they were of an urinous nature, the precipitate would be white and milky. so that having always by me some syrup of violets and some solution of sublimate, I can by the help of the first of those liquors discover in a trice, whether the propounded salt or saline body be of an acid nature or no; if it be, I need (you know) inquire no further; but if it be not, I can very easily, and as readily distinguish between the other two kinds of salts, by the white or orange-colour that is immediately produced, by letting fall a few drops or grains of the salt to be examined, into a spoonfull of the clear solution of sublimate. For example, it has been supposed by some eminently learned, that when sal armoniac being mingled with an alcali is forced from it by the fire in close vessels, the volatile salt that will thereby be obtained (if the operation be skilfully performed) is but a more fine and subtile sort of sal armoniac which, it is presumed, this operation does but more exquisitely purify than common solutions, filtrations, and coagulations. But this opinion may be easily shown to be erroneous, as by other arguments, so particularly by the lately delivered method of distinguishing the tribes of salts. For the saline spirit of sal-armoniac, as it is in many other manifest qualities very like the spirit of urine, so like, that it will in a trice make syrup of violets of a lovely green, turn a solution of good verdigrease into an excellent azure, and make the solution of a sublimate yield a white precipitate; insomuch that in most (for I say not all of the experiments) where I aim only at producing a sudden change of colour, I scruple not to use spirit of sal-amoniac when it is at hand, instead of spirit of urine, as indeed it seems chiefly to consist (besides the phlegm, that helps to make it fluid) of the volatile urinous salt (yet not excluding that of soot) that abounds in the sal armoniac and is set at liberty from the sea-salt wherewith it was formerly associated, and clogged, by the operation of the alcali, that divides the ingredients of sal armoniac, and retains that sea-salt with itself: what use may be made of the like way of exploration in that inquiry which puzzles so many modern Naturalists, whether the rich pigment (which we have often had occasion to mention) belongs to the vegetable or animal kingdom, you may find in another place, where I give you some account of what I tried about cochineal. But I think it needless to exemplify here our method by any other instances, many such being to be met with in divers parts of this treatise; but I will rather advertise you, that by this way of examining chymical liquors, you may not only in most cases conclude affirmatively, but in some cases negatively. As since spirit of wine, and, as far as I have tried, those chymical oils which artists call essential, did not (when I used them as I had used the several families of salts upon that syrup) turn syrup of violets red or green, nor the solution of sublimate white or yellow; I inferred it may thence be probably argued, that either they are destitute of salt, or have such as belongs not to either of the three grand families often already mentioned. When I went to examine the spirit of oak, or of such like concretes forced over through a retort, I found by this means amongst others, that (as I elsewhere show) those chymists are much mistaken in it, that account it a simple liquor, and one of their hypostatical principles. For not to mention what phlegm it may have, I found that with a few drops of one of this sort of spirits mixed with a good proportion of syrup of violets, I could change the colour and make it purplish, by the affinity of which colour to redness, I conjectured that this spirit had some acid corpuscles in it; and accordingly I found, that as it would destroy the blueness of a tincture of Lignum Nephriticum, so being put upon corals, it would corrode them, as common spirit of vinegar, and other acid liquors are wont to do. And farther to examine whether there were not a great part of the liquor that was not of an acid nature, having separated the four or vinegar-like part from the rest, which (if I mistake not) is far the more copious; we concluded, as we had conjectured, the other or remaining part, though it had a strong taste as well as smell, to be of a nature differing from that of either of the three sorts of salts above-mentioned, since it did as little as spirit of wine, and chymical oils, alter the colour either of syrup of violets or solution of sublimate: whence we also inferred, that the change that had been made of that syrup into a purple colour, was effected by the vinegar, that was one of the two ingredients of the liquor, which was wont to pass for a simple or uncompounded spirit. And, upon this account, it was of the spirit of oak (and the like concretes) freed from its vinegar, that I elsewhere told you, that I had not then observed it (and I have repeated the trial but very lately) to destroy the ceruleous tincture of Lignum Nephriticum. But this only en passant; for the chief thing I had to add was this: that by the same way may be examined and discovered divers changes that are produced in bodies, either by nature only, or by art; either of them being able, by changing the texture of some concretes I could name, to qualify them to operate after a new manner upon the above mentioned syrup, or solution, or both: and by this means, to tell you that, upon the by, I have been able to discover, that there may be made bodies, which though they run per deliquium, as readily as salt of tartar, belong, in other respects, not too the family of alcalies, much less to that of salsuginous or that of acid salts. Perhaps too, I may know a way of making a highly operative saline body, that shall neither change the colour of syrup of violets nor precipitate the solution of sublimate; and I can likewise, if I please, conceal by what liquors I perform such changes of colour, as I have been mentioning to you, by quite altering the texture of some ordinary chymical productions, the exploration of which is the main use of the fortieth experiment, which I think teaches not a little, if it teach us to discover the nature of those things (in reference to salt) that are obtained by the ordinary chymical analysis of mixed bodies, though perhaps there may be other bodies prepared by chymistry, which may have the same effects in the change of colours, and yet be produced not from what chymists call the resolution of bodies, but from their composition. But the discoursing of things of this nature is more proper for another place. I shall now only add, what might perhaps have been more seasonably told you before; that the reason why the way of exploration of salts hitherto delivered succeeds in the solution of sublimate, depends upon the particular texture of that solution, as well as upon the differing natures of the saline liquors employed to precipitate it. For gold dissolved in aqua regia, whether you precipitate it with oil of tartar, which is an alcali, or with spirit of urine, or sal armoniac, which belongs to the family of volatile salts, will either way afford a yellow substance: though with such an acid liquor as, I say not spirit of salt, the body that yields it, being upon the matter an ingredient of aqua regis, but oil of vitriol itself, I did not find that I could precipitate the metal out of the solution, or destroy the colour of it; though the same oil of vitriol would readily precipitate silver dissolved in aqua fortis. And if you dissolve pure silver in aqua fortis, and suffer it to shoot into crystals, the clear solution of these made in fair water, will afford a very white precipitate, whether it be made with an alcali, or an acid spirit, as that of fair; whereas, which may seem somewhat strange, with spirit of sal armioniac (that I used was made of quick-lime) I could obtain no such white precipitate: that volatile spirit, nor (as I remember) that of urine, scarce doing any more than striking down a very small quantity of matter, which was neither white nor whitish; so that the remaining liquor being suffered to evaporate till the superfluous moisture was gone, the greatest part of the metalline corpluscles with the saline ones that had imbibed them, concoagulated into salt, as is usual in such solutions, wherein the metal has not been precipitated.

OF kin to the last or fortieth experiment is another which I remember I have sometimes shewn to Virtuosi, that were pleased not to dislike it. I took spirit of urine made by fermentation, and with a due proportion of copper brought into small parts, I obtained a very lovely azure solution; and when I saw the colour was such as was requisite, pouring into a clean glass about a spoonful of this tincted liquor (of which I used to keep a quantity by me) I could, by shaking into it some drops of strong oil of vitriol, deprive it in a trice of its deep colour, and make it look like common water.

THIS experiment brings into my mind this other, which oftentimes succeeds well enough, though not quite so well as the former; namely, that if into about a small spoonful of a solution of good French verdigrease made in fair water, I dropt and shaked some strong spirit of salt, or rather dephlegmed aqua fortis, the greenness of the solution would be made in a trice almost totally to disappear, and the liquor held against the light would scarce seem other than clear or limpid, to any but an attentive eye: which is therefore remarkable, because we know that aqua fortis corroding copper, which is it that gives the colour to verdigrease, is wont to reduce it to a green blue solution. But if into the other altogether or almost colourless liquor I was speaking of, you drop a just quantity either of oil of tartar or spirit of urine, you shall find that after the ebullition is ceased, the mixture will disclose a lively colour, though somewhat differing from that which the solution of verdigrease had at first.

THAT the colour (Pyrophilus) of a body may be changed by a liquor which of itself is of no colour, provided it be saline, we have already manifested by a multitude of instances. Nor doth it seem so strange, because saline particles swimming up and down in liquors have been by many observed to be very operative in the production and change of colours. But divers of our friends, that are not acquainted with chymical operations, have thought it very strange that a white body, and a dry one too, should immediately acquire a rich new colour upon the bare affusion of spring-water destitute as well of adventitious salt as of tincture. And yet (Pyrophilus) the way of producing such a change of colours may be easily enough lighted on, by those that are conversant in the solutions of mercury. For we have tried, that though by evaporating a solution of quicksilver in aqua fortis, and abstracting the liquor till the remaining matter began to be well, but not too strongly dried, fair water poured on the remaining calx made it but somewhat yellowish; yet when we took good quicksilver, and three or four times its weight of oil of vitriol, in case we in a glass retort placed in sand drew off the saline menstruum from the metalline liquor, till there remained a dry calx at the bottom, though this precipitate were a snow-white body, yet upon pouring on it a large quantity of fair water, we did almost in a moment perceive it to pass from a milky colour to one of the loveliest light yellows that ever we had beheld. Nor is the turbith mineral, that chymists extol for its power to salivate, and for other virtues, of a colour much inferior to this, though it be often made with a differing proportion of the ingredients, a more troublesome way. For Beguinus, who calls it Mercurius preacipitatus optimus, takes to one part of quicksilver but two of liquor, and that is rectified oil of sulphur, which is (in England at least) far more scarce and dear than oil of vitriol; he also requires a previous digestion, two or three cohobations, and frequent ablutions with hot distilled water; with other prescriptions, which though they may conduce to the goodness of the medicine, which is that he aims at, are troublesome, and, our trials have informed you, unnecessary to the obtaining the lemon colour, which he regards not. But though we have very rarely seen either in painters shops, or elsewhere, a finer yellow than that which we have divers times this way produced (which is the more considerable, because durable and pleasant yellows are very hard to be met with, as may appear by the great use which painters are for its colour's sake fain to make of that pernicious and heavy mineral, orpiment;) yet I fear our yellow is too costly, to be like to be employed by painters, unless about choice pieces of work, nor do I know how well it will agree with every pigment, especially, with oiled colours. And whether this experiment, though it have seemed somewhat strange to most we have shewn it to, be really of another nature than those wherein saline liquors are employed, may, as we formerly also hinted, be so plausibly doubted, that whether the water poured on the calx, do barely by imbibing some of its saline parts alter its colour, by altering its texture, or whether by dissolving the concoagulated salts, it does become a saline menstruum, and, as such, work upon the mercury, I freely leave to you, Pyrophilus, to consider. And that I may give you some assistance in your inquiry, I will not only tell you, that I have several times with fair water washed from this calx, good store of strongly tasted corpuscles, which by the abstraction of the menstruum, I could reduce into salt; but I will also subjoin an experiment, which I devised, to shew among other things, how much a real and permanent colour may be as it were drawn forth by a liquor that has neither colour, nor so much as saline or other active parts, provided it can but bring the parts of the body it imbibes to convene into clusters disposed after the manner requisite to the exhibiting of the emergent colour. The experiment was this.

WE took good common vitriol, and having beaten it to powder, and put it into a crucible, we kept it melted in a gentle heat, till by the evaporation of some parts, and the shuffling of the rest, it had quite lost its former colour; what remained we took out, and found it to be a friable calx, of a dirty grey. On this we poured fair water, which it did not colour green or blue, but only seemed to make a muddy mixture with it, then stopping the phial wherein the ingredients were put, we let it stand in a quiet place for some days, and after many hours the water having dissolved a good part of the imperfectly calcined body, the vitriolate corpuscles swimming to and fro in the liquor, had time by their opportune occursions to constitute many little masses of vitriol, which gave the water they impregnated a fair vitriolate colour; and this liquor being poured off, the remaining dirty powder did in process of time communicate the like colour, but not so deep, to a second parcel of clear water that we poured on it. But this experiment, Pyrophilus, is (to give you that hint by the way) of too luciferous a nature to be fit to be fully prosecuted, now that I am in haste, and willing to dispatch what remains. And we have already said of it, as much as is requisite to our present purpose.

IT may (Pyrophilius) somewhat contribute towards the shewing how much some colours depend upon the less or greater mixture, and (as it were) contemperation of the light with shades, to observe how that sometimes the number of particles, of the same colour, received into the pores of a liquor, or swimming up and down in it, do seem much to vary the colour of it. I could here present you with particular instances to show, how in many (if not most) consistent bodies, if the colour be not a light one, as white, yellow, or the like, the closeness of parts in the pigments makes it look blackish, though when it is displayed and laid on thinly, it will perhaps appear to be either blue, or green, or red.

But the colours of consistent pigments, not being those which the preamble of this experiment has led you to expect examples in, I shall take the instances I am now to give you, rather from liquors than dry bodies. If then you put a little fair water into a clear and slender phial (or rather into one of those pipes of glass, which we shall by and by mention;) and let fall into it a few drops of a strong decotion or infusion of cochineal, or (for want of that) of brazil; you may see the tincted drops descend like little clouds into the liquor; through which, if, by shaking the phial, you diffuse them, they will turn the water either of a pink colour, or like that which is wont to be made by the washing of raw flesh in fair water; by dropping a little more of the decoction, you may heighten the colour into a fine red, almost like that which ennobles rubies; by continuing the affusion, you may bring, the liquor to a kind of a crimson, and afterwards to a dark and opacous redness, somewhat like that of clotted blood. And in the passage of the liquor from one of these colours to the other, you may observe, if you consider it attentively, divers other less noted colours belonging to red, to which it is not easy to give names; especially considering how much the proportion of the decoction to the fair water; and the strength of that decoction, together with that of the trajected light and other circumstances, may vary the phænomena of this experiment. For the convenienter making whereof, we use, instead of a phial, any slender pipe of glass of about a foot or more in length, and about the thickness of a man's little finger; for, if leaving one end of this pipe open, you seal up the other hermetically (or at least stop it hermetically with a cork well fitted to it, and overlaid with hard sealing wax melted, and rubbed upon it;) you shall have a glass, wherein may be observed the variations of the colours of liquors much better than in large phials, and wherein experiments of this nature may be well made with very small quantities of liquor. And if you please, you may in this pipe produce variety of colours in the various parts of the liquor, and keep them swimming upon one another unmixed for a good while. And some have marvelled to see, what variety of colours we have sometimes (but I confess rather by chance than skill) produced in those glasses, by the bare infusion of brazil, variously diluted with fair water, and altered by the infusion of several chymical spirits and other saline liquors devoid themselves of colour: and when the whole liquor is reduced to an uniform degree of colour, I have taken pleasure to make that very liquor seem to be of colours gradually differing, by filling with it glasses of a conical figure (whether the glass have its basis in the ordinary position, or turned upwards). And yet you need not glasses of an extraordinary shape, to see an instance of what the various mixture of light and shadow can do in the diversifying of the colour. For if you take but a large round phial, with a somewhat long and slender neck, and filling it with our red infusion of brazil, hold it against the light you will discern a notable disparity betwixt the colour of that part of the liquor which is in the body of the phial, and that which is more pervious to the light in the neck. Nay, I remember, that I once had a glass and a blue liquor (consisting chiefly, or only, if my memory deceive me not, of a certain solution of verdigrease) so fitted for my purpose, that though in other glasses the experiment would not succeed, yet when that particular glass was filled with that solution, in the body of the phial it appeared of a lovely blue, and in the neck (where the light did more dilute the colour) of a manifest green; and though I suspected there might be some latent yellowness in the substance of the neck of the glass, which might with the blue compose that green, yet was I not satisfied myself with my conjecture, but the thing seemed odd to me, as well as to divers curious persons to whom it was shown. And I lately had a broad piece of glass, which being looked on against the light seemed clear enough, and held from the light appeared very lightly discoloured; and yet it was a piece knocked off from a great lump of glass, to which if we rejoined it, where it had been broken off, the whole mass was as green as grass. And I have several times used bottles and stopples that were both made (as those, I had them from, assured me) of the very same metal; and whilst the bottle appeared but inclining towards a green, the stopple (by reason of its great thickness) was of so deep a colour, that you would hardly believe they could possibly be made of the same materials. But to satisfy some ingenious men, on another occasion, I provided myself of a flat glass (which I yet have by me) with which if I look against the light with the broad side obverted to the eye, it appears like a good ordinary window-glass; but if I turn the edge of it to my eye, and place my eye in a convenient posture in reference to the light, it may contend for deepness of colour with an emerald. And this greenness puts me in mind of a certain thickish, but not consistent pigment I have sometimes made, and can show you when you please, which being dropped on a piece of white paper appears, where any quantity of it is fallen, of a somewhat crimson colour; but being with one's finger spread thinly on the paper, does presently exhibit a fair green: which seems to proceed only from its disclosing its colour upon the extenuation of its depth into superficies, if the change be not somewhat helped by the colours degenerating upon one or other of the accounts formerly mentioned. Let me add, that having made divers trials with that blue substance, which in painters shops is called Litmase, we have sometimes taken pleasure to observe, that being dissolved in a due proportion of fair water, the solution either opposed to the light, or dropped upon white paper, did appear of a deep colour betwixt crimson and purple; and yet that being spread very thin on the paper, and suffered to dry on there, the paper was wont to appear stained of a fine blue. And to satisfy myself, that the diversity came not from the paper, which one might suspect capable of imbibing the liquor, and altering the colour, I made the trial upon a flat piece of purely white glazed earth (which I sometimes make use of about experiments of colours) with an event not unlike the former.

AND now I speak of litmase, I will add, that having this very day taken a piece of it, that I had kept by me these several years, to make trials about colours, and having let fall a few drops of the strong infusion of it in fair water, into a fine crystal glass, shaped like an inverted cone, and almost full of fair water, I had now (as formerly) the pleasure to see, and to shew others, how these few tincted drops variously dispersing themselves through the limpid water, exhibited divers colours, or varieties of purple and crimson. And when the corpuscles of the pigment seemed to have equally diffused themselves through the whole liquor, I then by putting two or three drops of spirit of salt, first made an odd change in the colour of the liquor, as well as a visible commotion among, its small parts, and in a short time changed it wholly into a very glorious yellow, like that of a topaz. After which if I let fall a few drops of the strong and heavy solution of pot-ashes, whose weight would quickly carry it to the sharp bottom of the glass, there would soon appear four very pleasant and distinct colours; namely, a bright, but dilute colour at the picked bottom of the glass; a purple, a little higher; a deep and glorious crimson (which crimson seemed to terminate the operation of the salt upward) in the confines betwixt the purple and the yellow; and an excellent yellow, the same that before ennobled the whole liquor, reaching from thence to the top) of the glass. And if I pleased to pour very gently a little spirit of sal-armoniac upon the upper part of this yellow, there would also be a purple or a crimson, or both generated there, so that the unaltered part of the yellow liquor appeared intercepted betwixt the two neighbouring colours.

MY scope in this third experiment (Pyrophilus) is manifold, as first to invite you to be wary in judging of the colour of liquors in such glasses as are therein recommended to you, and consequently as much, if not more, when you employ other glasses. Secondly, that you may not think it strange, that I often content myself to rub upon a piece of white paper the juice of bodies I would examine; since not only I could not easily procure a sufficient quantity of the juices of divers of them, but in several cases the trials of the quantities of such juices in glasses would make us more liable to mistakes, than the way that in those cases I have made use of. Thirdly, I hope you will by these and divers other particulars delivered in this treatis, be easily induced to think that I may have set down many phænomena, very faithfully, and just as they appeared to me, and yet by reason of some unheeded circumstance in the conditions of the matter, and in the degree of light, or the manner of trying the experiment, you may find some things to vary from the relations I make of them. Lastly, I designed to give you an opportunity to free yourself from the amazement which posseses most men, at the tricks of those mountebanks that are commonly called water-drinkers. For though not only the vulgar, but even many persons that are far above that rank, have so much admired to see a man, after having drunk a great deal of fair water, to spurt it out again in the form of claret-wine, sack and milk, that they have suspected the intervening of magic, or some forbidden, means to effect what they conceived above the power of art; yet having once by chance had occasion to oblige a wanderer, that made profession of that and other juggling tricks, I was easily confirmed by his ingenuous confession to me, that this so much admired art, indeed consisted rather in a few tricks, than in any great skill, in altering the nature and colours of things. And I am easy to be persuaded, that there may be a great deal of truth in a little pamphlet printed divers years ago in English, wherein the author undertakes to discover, and that (if I mistake not) by the confession of some of the accomplices themselves, that a famous water-drinker, then much admired in England, performed his pretended transmutations of liquors by the help of two or three inconsiderable preparations and mixtures of not unobvious liquors, and chiefly of an infusion of brazil variously diluted and made pale or yellowish (and otherwise altered) with vinegar; the rest of their work being performed by the shape of the glasses, by craft and legerdemain. And for my part, that which I marvel at in this business, is the drinkers being able to take down so much water, and spout it out with that violence; though custom, and a vomit seasonably taken before hand, may in some of them much facilitate the work. But as for the changes made in the liquors, they were but few and slight in comparison of those, that the being conversant in chymical experiments, and dextrous in applying them to the transmuting of colours, may easily enough enable a man to make, as even what has been newly delivered in this, and the foregoing experiment; especially if we add to it the things contained in the twentieth, the thirty-ninth, and the fortieth experiments, may perhaps have already persuaded you.

YOU may, I presume, (Pyrophilus) have taken notice, that in this whole treatise I purposely decline (as far as I well can) the mentioning of elaborate chymical experiments, for fear of frighting you by their tediousness and difficulty; but yet, in comfirmation of what I have been newly telling you about the possibility of varying the colours of liquors, better than the water-drinkers are wont to do, I shall add, that Helmont used to make a preparation of steel, which a very ingenious chymist, his son's friend, whom you know, sometimes employs for a succedaneum to the Spaw-waters, by diluting this essentia martis 1iquida (as he calls it) with a due proportion of water. Now that for which I mention to you this preparation (which as he communicated to me, I know he will not refuse to Pyrophilus) is this, that though the liquor (as I can shew when you please) be almost of the colour of a German (not an Oriental) amethist, and consequently remote enough from green, yet a very few drops being let fall into a large proportion of good Rhenish, or (in want of that) white-wine (which yet does not quite so well) immediately turned the liquor into a lovely green, as I have not without delight shown several curious persons, By which phenomenon you may learn, among other things, how requisite it is in experiments about the changes of colours heedfully to mind the circumstances, of them: for water will not, as I have purposely tried, concur to the production of any such green, nor did it give that colour to moderate spirit of wine, wherein I purposely dissolved it, and wine itself is a liquor that few would suspect of being able to work suddenly any such change in a metalline reparation of this nature. And to satisfy myself that this new colour proceeds rather from the peculiar texture of the wine, than from any greater acidity, that Rhenish or white-wine (for that may not absurdly be suspected) has in comparison of water; I purposely sharpened the solution of this essence in fair water, with a good quantity of spirit of salt, notwithstanding, which, the mixture acquired no greenness. And to vary the experiment a little, I tried, that if into a glass of Rhenish wine made green by this essence, I dropped an alcalizate solution, or urinous spirit, the wine would presently grow turbid, and of an odd dirty colour: but if instead of dissolving the essence in wine, I dissolved it in fair water, sharpened perhaps with a little spirit of salt, then either the urinous spirit of sal armoniac, or the solution of the fixed salt of pot-ashes, would immediately turn it of a yellowish colour, the fixed or urinous salt precipitating the vitriolate substance contained in the essence. But here I must not forget to take notice of a circumstance that deserves to be compared with some part of the foregoing experiment; for whereas our essence imparts a greenness to wine, but not to water, the industrious Olaus Wormius in his late Musæum tells us of a rare kind of turnsol, which he calls Bezetta Rubra, given him by an apothecary that knew not how it was made, whose lovely redness would be easily communicated to water, if it were immersed in it; but scarce to wine, and not at all to spirit of wine: in which last circumstance it agrees with what I lately told you of our essence, notwithstanding their disagreement in other particulars.

WE have often taken notice, as of a remarkable thing, that metals, as they appear to the eye, before they come to be farther altered by other bodies, do, exhibit colours very different from those which the fire and the menstruum, either apart, or both together, do produce in them; especially considering that these metalline bodies are after all these disguises reducible not only to their former metalline consistence, and other more radical properties, but to their colour too; as if nature had given divers metals to each of them a double colour, an external, and an internal. But though upon a more attentive consideration of this difference of colours, it seemed probable to me that divers (for I say not all) of those colours which we have just now called internal, are rather produced by the coalition of metalline particles with those of the salts, or other bodies employed to work on them, than by the bare alteration of the parts of the metals themselves; and though therefore we may call the obvious colours natural or common, and the others adventitious: yet because such changes of colours, from whatsoever cause they be resolved to proceed, may be properly enough taken in to illustrate our present subject, we shall not scruple to take notice of some of them, especially because there are among them such as are produced without the intervention of saline menstruums. Of the adventitious colours of metalline bodies the chief sorts seem to be these three: the first, such colours are produced without other additaments by the action of the fire upon metals. The next, such as emerge from the coalition of metalline particles with those of some menstruum employed to corrode a metal or precipitate it; and the last, the colours afforded by metalline bodies either colliquated with, or otherwise penetrating into, other bodies, especially fusible ones. But these (Pyrophilus) are only, as I told you the chief sorts of the adventitious colours of metals, for there may others belong to them, of which I shall hereafter have occasion to take notice of some, and of which also there possibly may be others that I never took notice of.

AND to begin with the first sort of colours, it is well enough known to chymist that tin being calcined by fire alone is wont to afford a white calx, and lead calcined by fire alone affords that most common red powder we call minium: copper also calcined per se, by a long or violent fire, is wont to yield (as far as I have had occasion to take notice of it) a very dark or blackish powder; that iron likewise may by the action of reverberated flames be turned into a colour almost like that of saffron, may be easily deduced from the preparation of that powder, which by reason of its colour and of the metal it is made of, is by chymists called Crocus Martis per se. And that mercury, made by the stress of fire, may be turned into a red powder, which chymists call precipitate per se, I elsewhere more particularly declare.

IT is not unworthy the admonishing you (Pyrophilus) and it agrees very well with our conjectures about the dependence of the change of a body's colour upon that of its texture, that the same metal may by the successive operation of the fire receive divers adventitious colours, as is evident in lead, which before it come to so deep a colour as that of minium, may pass through divers others.

NOT only the calces, but the glasses of metals, vitrified per se, may be of colours differing from the natural or obvious colour of the metal; as I have observed in the glass of lead, made by long exposing crude lead to a violent fire, and what I have observed about the glass or slag of copper (of which I can show you some of an odd kind of texture) may be elsewhere more conveniently related. I have likewise seen a piece of very dark glass, which an ingenious artificer that showed it me professed himself to have made of silver alone by an extreme violence (which seems to be no more than is needful) of the fire.

MINERALS also by the action of the fire may be brought to afford colours very differing from their own, as I not long since noted to you about the variously coloured flowers of antimony; to which we may add the whitish grey-colour of its calx, and the yellow or reddish colour of the glass, whereinto that calx may be fluxed.

AND I remember, that I elsewhere told you, that vitriol calcined with a very gentle heat, and afterwards with higher and higher degrees of it, may be made to pass through several colours before it descends to a dark purplish colour, whereto a strong fire is wont at length to reduce it. But to insist on the colours produced by the operation of fire upon several minerals, would take up far more time than I have now to, spare.

THE adventitious colours produced upon metals, or rather with them, by saline liquors, are many of them so well known to chymists, that I would not here mention them, but that besides a not un-needed testimony, I can add something of my own, to what I shall repeat about them; and divers experiments which are familiar to chymists, are as yet unknown to the greatest part of ingenious men.

THAT gold dissolved in aqua regia ennobles the menstruum with its own colour, is a thing that you cannot (Pyrophilus) but have often seen, The solutions of mercury in aqua fortis are not generally taken notice of, to give any notable tincture to the menstruum; but sometimes when the liquor first falls upon the quicksilver, I have observed a very remarkable, though not durable greenness, or blueness to be produced; which is a phenomenon not unfit for you to consider, though I have not now the leisure to discourse upon it. Tin corroded by aqua fortis till the menstruum will work no farther on it, becomes exceeding white; but, as we elsewhere note, does very easily of itself acquire the consistence, not of a metalline calx, but of a coagulated matter, which we have observed with pleasure to look so like, either to curdled milk, or curdled whites of eggs, that a person unacquainted with such solutions may easily be mistaken in it. But when I purposely prepared a menstruum that would dissolve it as aqua fortis dissolves silver, and not barely corrode it, and quickly let it fall again, I remember not that I took notice of any particular colour in the solution, as if the more whitish metals did not much tinge their menstruums, though the conspicuously coloured metals as gold, and copper, do. For lead dissolved in spirit of vinegar or aqua fortis gives a solution clear enough, and if the menstruum be abstracted appears either diaphanous or white. Of the colour of iron we have elsewhere said something: and it is worth noting, that though if that metal be dissolved in oil of vitriol diluted with water, it affords a salt or magistery so like in colour, as well as some other qualities, to other green vitriol, that chymists do not improperly call it Vitriolum Martis; yet I have purposely tried, that, by changing the menstruum, and pouring upon the filings of steel, instead of oil of vitriol, aqua fortis (whereof, as I remember, I used four parts to one of the metal) I obtained not a green, but a saffron coloured solution; or rather a thick liquor of a deep but yellowish red. Common silver, such as is to be met with in coins, being dissolved in aqua fortis, yields a solution tincted like that of copper, which is not to be wondered at, because in the coining of silver, they are wont (as we elsewhere particularly inform you) to give it an allay of copper, and that, which is sold in shops for refined silver, is not (so far as we have tried) so perfectly free from that ignobler metal, but that a solution of it in aqua fortis will give a venereal tincture to the menstruum. But we could not observe upon the solution of some silver, which was perfectly refined (such as some that we have, from which eight or ten times its weight of lead has been, blown off) that the menstruum, though held against the light in a crystal phial, did manifestly disclose any tincture, only it seemed sometimes not to be quite destitute of a little, but very faint blueishness.

BUT here I must take notice, that of all the metals, there is not any, which doth so easily and constantly disclose its unobvious colour, as copper doth. For not only in acid menstruums, as aqua fortis and spirit of vinegar, it gives a blueish green solution, but if it be almost any way corroded, it appears of one of those two colours, as may be observed in verdigrease made several ways, in that odd preparation of Venus, which we elsewhere teach you to make with sublimate, and in the common vitriols of Venus delivered by chymists. And so constant is the disposition of copper, notwithstanding the disguise artists put upon it, to disclose the colour we have been mentioning that we have by forcing it up with sal armoniac obtained a sublimate of a blueish colour. Nay, a famous Spagyrist affirms, that the very mercury of it is green; but till he teach us an intelligible way of making such a mercury, we must content ourselves to inform you, that we have had a cupreous body, that was precipitated out of a distilled liquor, that seemed to be the sulphur of Venus, and seemed, even when flaming, of a greenish colour. And indeed copper is a metal so easily wrought upon by liquors of several kinds, that I should tell you, I know not any mineral, that will concur to the production of such a variety of colours as copper dissolved in several menstruums, as spirit of vinegar, aqua fortis, aqua regis, spirit of nitre, of urine, of soot, oils of several kinds, and I know not how many other liquors, if the variety of somewhat differing colours (that copper will be made to assume, as it is wrought upon by several liquors) were not comprehended within the limits of greenish blue, or blueish green.

AND yet I must advertise you (Pyrophilus) that being desirous to try, if I could not make with crude copper a green solution without the blueishness, that is wont to accompany its vulgar solutions, I bethought myself of using two menstruums, which I had not known employed to work on this metal, and which I had certain reasons to make trial of, as I successfully did. The one of these liquors (if I much misremember not) was spirit of sugar distilled in a retort, which must be warily done (if you will avoid breaking your glasses;) and the other, oil or spirit of turpentine, which affords a fine green solution, that is useful to me on several occasions. And yet to shew, that the adventitious colour may result, as well from the true and permanent copper itself, as the salts wherewith it is corroded, I shall add, that if you take a piece of good Dantzick copperas, or any other vitriol, wherein Venus is predominant, and having moistened it in your mouth, or with fair water, rub it upon a whetted knife, or any other bright piece of steel or iron, it will (as we have formerly told you) presently stain the steel with a reddish colour, like that of copper; the reason of which we must not now stay to inquire.

I PRESUME you may have taken notice (Pyrophilus) that I have borrowed some of the instances, mentioned in this 47th experiment from the laboratories of chymists; and because in some (though very few) other passages of this essay, I have likewise made use of experiments mentioned also by some spagyrical writers, I think it not amiss to represent to you on this occasion once for all some things, besides those which I intimated in the preamble of this present experiment. For besides, that it is very allowable for a writer to repeat an experiment, which he invented not, in case he improve it; and besides that many experiments familiar to chymists are unknown to the generality of learned men, who either never read chymical processes, or never understood their meaning, or never durst believe them; besides these things, I say, I shall represent, that, as to the few experiments I have borrowed from the chymists, if they be very vulgar, it would perhaps be difficult to ascribe each of them its own author, and it is more than the generality of chymists themselves can do: and if they be not of very known and familiar practice among them, unless the authors, wherein I found them, had given me cause to believe themselves had tried them, I know not why I might not set them down, as a part of the phænomena of colours, which I present you; many things unanimously enough delivered as matters of fact by I know not how many chymical writers, being not to be relied on, upon the single authority of such authors: for instance, as some Spagyrists deliver (perhaps amongst several deceitful processes) that saccharum Saturni with spirit of turpentine will afford a balsam, so Beguinus and many more tell us, that the same concrete (saccharum Saturni) will yield an incomparably fragrant spirit, and a pretty quantity of two several oils. And yet since many have complained, as well as I have done, that they could find no such odoriferous, but rather an ill scented liquor, and scarce any oil in their distillation of that sweet vitriol, a wary person would as little build any thing on what they say of the former experiment, as upon what they aver of the latter I and therefore I scrupled not to mention this red balsam, of which I have not seen any (but what I made) among my other experiments about redness.

WE have sometimes had the curiosity to try, what colours minerals, as tin-glass, antimony, spelter, &c. would yield in several menstruums; nor have we forborn to try the colours of stones, of which that famous one (which Helmont calls Paracelsus's Ludus) though it be digged out of the earth, and seem a true stone, has afforded in menstruums capable to dissolve so solid a stone, sometimes a yellowish, sometimes a red solution, of both which I can shew you. But though I have from minerals obtained with several menstruums very differing colours, and some such as, perhaps, you would be surprized to see drawn from such bodies; yet I must now pass by the particulars, being desirous to put an end to this treatise, before I put an end to your patience and my own.

AND yet before I pass to the next experiment, I must put you in mind, that the colours of metals may in many cases be further altered by employing, either precipitating salts, or other convenient substances to act upon their solutions. Of this you may remember that I have given you several instances already, to which may be added such as these; that if quicksilver be dissolved in aqua fortis, and precipitated out of the solution, either with water impregnated with sea-salt, or with the spirit of the concrete, it falls to the bottom in the form of a white powder; whereas if it be precipitated with an alcali, it will afford a yellowish or tawny powder; and if there be no precipitation made, and the menstruum be drawn off with a convenient fire, the corroded mercury will remain in the bottom, in the form of a substance, that may be made to appear of differing colours by differing degrees of heat: as I remember, that lately having purposely abstracted aqua fortis from some quicksilver, that we had dissolved in it, so that there remained a white calx, exposing that to several degrees of fire, and afterwards to a naked one, we obtained some new colours., and at length the greatest part of the calx lying at the bottom of the phial, and being brought partly to a deep yellow, and partly to a red colour, the rest appeared elevated to the upper part and neck of the phial, some in the form of reddish, and some of an ash-colour sublimate. But of the differing colours, which by differing ways and working of quicksilver with fire, and saline bodies, may be produced in precipitates, I may elsewhere have ocasion to take further notice. I also told you not long since, that if you corrode quicksilver with oil of vitriol instead of aqua fortis, and abstract the menstruum, there will remain a white calx, which by the affusion of fair water presently turns into a lemon colour. And even the succedaneum to a menstruum may sometimes serve the turn, to change the colours of a metal. The lovely red, which painters call vermilion, is made of mercury, which is of the colour of silver; and of brimstone, which is of the colour of silver; and of brimstone, which is of kin to that of gold, sublimed up together in a certain proportion, as is vulgarly known to Spagyrists

THE third chief sort of the adventitious colours of metals is that, which is produced by associating them (especially when calcined) with other fusible bodies, and principally Venice, and other fine glass, devoid of colour.

I HAVE formerly given you an example, whereby it may appear, that a metal may impart to glass; a colour much differing from its own, when I told you how with silver I had given glass a lovely golden colour. And I shall now add, that I have learned from one of the chief artificers, that sells painted glass, that those of his trade colour it yellow with a preparation of the calx of silver. Though all having lately had occasion among other trials to mingle a few grains of shell-silver (such as is employed with the pencil and pen) with a convenient proportion of powdered crystal glass, having kept them two or three hours in fusion, I was surprized to find the colliquated mass to appear, upon breaking the crucible, of a lovely saphirine blue; which made me suspect my servant might have brought me a wrong crucible: but he constantly affirmed it to be the same, wherein the silver was put, and considerable circumstances countenanced his assertion, so that till I have opportunity to make farther trial, I cannot but suspect, either that silver, which is not (which is not very probable) brought to a perfect fusion and colliquation with glass, may impart to it other colours than when nealed upon it; or else (which is less unlikely) that though silver-beaters usually chuse the finest coin they can get, as that which is most extensive under the hammer, yet the silver leaves, of which this shell-silver was made, might retain so much copper, as to enable it to give the predominant tincture to the glass.

FOR, I must proceed to tell you (Pyroplilus) as another instance of the adventitious colours of metals, that, which is something, strange, namely, that, though copper calcined per se affords but a dark and basely coloured calx, yet the glass-men do with it, as themselves inform me, tinge their glass green. And I remember, that when once we took some crude copper, and by frequent ignition quenching it in water had reduced it to a dark and ill-coloured powder, and afterwards kept it in fusion in about a hundred times its weight of fine glass, we had, though not a green, yet a blue coloured mass; which would perhaps have been green, if we had hit right upon the proportion of the materials, and the degree of fire, and the time wherein it ought to be kept in fusion; to plentifully does that metal abound in a venereal tincture, as artists call it, and in so many ways does it disclose that richness. But though copper do, as we have said, give somewhat near the like colour to glass, which it does to aqua fortis, yet it seems worthy to enquire, whether these new colours, which mineral bodies disclose in melted glass, proceed from the coalition of the corpusc1es of the mineral with the particles of the glass as such, or from the action (excited or actuated by fire) of the alcalizate salt (which is a main ingredient of glass) upon the mineral body, or from the concurrence of both these causes, or else from any other. But to return to that which we were saying, we may observe, that putty made by calcining together a proportion of tin and lead, as it is itself a white calx, so does it turn the pitta di crystello (as the glass-men call the matter of the purer sort of glass, wherewith it is colliquated) into a white mass; which, if it be opacous enough, is employed, as we elsewhere declare, for white amel. But of the colours, which the other metals may be made to produce in colourless glass, and other vitrifiable bodies, that have native colours of their own, I must leave you to inform yourself upon trial; or at least must forbear to do it till another time, considering how many annotations are to follow, upon what has in this and the two former experiments been said already.

WHEN the materials of glass being melted with calcined tin, have composed a mass undiaphanous and white, this white amel is as it were the basis of all those fine concretes, that goldsmiths and several artificers employ in the curious art of enamelling. For this white and fusible substance will receive into itself, without spoiling them, the colours of divers other mineral substances, which like it will endure the fire.

SO that as by the present (XLVIII) experiment it appears, that divers minerals will impart to fusible masses colours differing from their own; so by the making and compounding of amels, it may appear, that divers bodies will both retain their colour in the fire, and impart the same to some others wherewith they were vitrified, and in such trials as that mentioned in the seventeenth experiment, where I told you, that even in amels a blue and yellow will compound a green. It is pretty to behold not only that some colours are of so fixed a nature, as to be capable of mixture without receiving any detriment by the fire, that does so easily destroy or spoil those of other bodies; but mineral pigments may be mingled by fire little less regularly and successfully, than in ordinary dying salts, the vulgar colours are wont to be mingled by the help of water.

It is not only metalline, but other mineral bodies, that may be employed, to give tinctures unto glass; and it is worth noting how small a quantity of some mineral substances will tinge a comparatively vast proportion of glass; and we have sometimes attempted to colour glass, even with precious stones, and had cause to think the experiment not cast away. And it is known by them, that have looked into the art of glass, that the artificers used to tinge their glass blue with that dark mineral zaffora (some of my trials on which I elsewhere acquaint you) which some would have to be a mineral earth, others of stone, and others neither the one nor the other, but which is confessedly of a dark, but not a blue colour, though it be not agreed of what particular colour it is. It is likewise though a familiar yet a remarkable practice among those, that deal in the making of glass, to employ (as some of themselves have informed me) what they call manganess, and some authors call Magnesia (of which I make particular mention in another treatise) to exhibit in glass not only other colours than its own (which is so like in darkness or blackishness to the loadstone, that is given by mineralists for one of the reasons of its Latin name) but colours differing, from one another. For though they use it (which is somewhat strange) to clarify their glass, and free it from that blueish greenish colour, which else it would too often be subject to; yet they also employ it in certain proportions, to tinge their glass both with red colour, and with a purplish or murry; and putting in a greater quantity, they also make with it that deep obscure glass, which is wont to pass for black, which agrees very well with, and may serve to confirm what we noted near the beginning of the 44th experiment, of the seeming blackness of those bodies, that are over-charged with the corpuscles of such colours, as red, or blue, or green, &c. And as by several metals and other minerals we can give various colours to glass, so on the other side, by the differing colours, that mineral ores, or other mineral powders, being melted with glass, disclose in it, a good conjecture may be oftentimes made of the metal or known mineral, that the ore proposed either holds, or is most of kin to. And this easy way of examining ores may be in some cases of good use, and is not ill delivered by Glauber, to whom I shall at present refer you for a more particular account of it: unless your curiosity command also what I have observed about these matters. Only I must here advertise you that great circumspection is requisite to keep this way from proving fallacious, upon the account of the variations of colour, that may be produced by the differing proportions, that may be used betwixt the ore and the glass, by the richness or poorness of the ore itself, by the degree of fire, and especially by the length of time, during which the matter is kept in fusion; as you will easily gather from what you will quickly meet with in the following annotation upon this 48th experiment.

THERE is another way, and differing enough from those already mentioned, by which metals may be brought to exhibit adventitious colours: for by this, the metal does not so much impart a colour to another body, as receive a colour from it, or rather both bodies do by the new texture resulting from their mistion produce a new colour. I will not insist to this purpose upon the examples afforded us by yellow orpiment, and common sea-salt, from which, sublimed together, chymists unanimously affirm their white or crystalline arsenic to be made: but it is not unworthy our noting, that though yellow orpiment be acknowledged to be the copiousest by far of the two ingredients of arsenic, yet this last named body being duly added to the highest coloured metal copper, when it is in fusion, gives it whiteness both within and without. Thus Lapis Calaminaris changes and improves the colour of copper, by turning it into brass. And I have sometimes, by the help of zink duly mixed after a certain manner, given copper one of the richest golden colours, that ever I have seen the best true gold ennobled with. But pray have a care, that such hints fall not into any hands, that may misemploy them.

UPON the knowledge of the differing ways of making minerals and metals produce their adventitious colours in bodies capable of vitrification, depends the pretty art of making what chymists by a barbarous word are pleased to call Amanses, that is, counterfeit or factitious gems as emeralds, rubies, saphires, topazes, and the like. For in the making of these, though pure sand or calcined crystal give the body, yet it is for the most part some metalline or mineral calx, mingled in a small proportion, that gives the colour. But though I have many years since taken delight to divert myself with this pleasing art, and have seen very pretty productons of it, yet besides that I fear I have now forgot most of the little skill I had in it, this is no place entertain you with what would rather take up an entire discourse than be comprehend in an annotation. Wherefore the few things, which I shall here take notice of to you, are only what belong to the present argument, namely,

FIRST, That I have often observed, that calcined lead colliquated with fine white sand or crystal, reduced by ignitions and subsequent extinctions in water to a subtile powder, will of itself be brought by a due decoction to give a clear mass coloured. like a German amethyst. For though this glass of lead is looked upon by them, that know no better way of making Amanses, as the grand work of them all; yet, which is an inconvenience, that much blemishes this way, the calcined lead itself does not only afford matter to the Amanses, but has also as well as other metals a colour of its own, which, as I was saying, I have often found to be like that of German (as many call them) not Eastern amethysts.

SECONDLY, That nevertheless this colour may be easily overpowered by those of divers other mineral pigments (if I may so call them) so that with glass of lead you may emulate (for instance) the fresh and lovely greenness of an emerald, though in divers cases the colour, which the lead itself upon vitrification tends to, may vitiate that of the pigment, which you would introduce into the mass.

THIRDLY, That so much even these colours depend upon texture, that in the glass of lead itself made of about three parts of litharge or minium colliquated with one of very finely powdered crystal or sand, we have taken pleasure to make the mixture pass through differing colours, as we kept it more or less in the fusion. For it was not usually till after a pretty long decoction, that the mass attained to the amethystine colour.

FOURTHLY and lastly, That the degrees of coction and other circumstances may so vary the colour produced in the same mass, that in a crucible that was not great I have had fragments of the same mass, in some of which, perhaps not so big as a hazel-nut, you may discern four distinct colours.

YOU may remember (Pyrophilus) that when I mentioned the three sorts of adventisious colours of metals, I mentioned them but as the chief, not the only. For there may be other ways, which though they do not in so strict a sense belong to the adventitious colours of metals, may not inconveniently be reduced to them. And of these I shall name now a couple, without denying, that there may be more.

THE first may be drawn from the practice of those, that dye scarlet. For the famousest master in that art either in England or Holland, has confessed to me, that neither others nor he can strike that lovely colour, which is now wont to be called the Bow-dye, without their materials be boiled in vessels, either made of, or lined with a particular metal. But of what I have known attempted in this kind, I must not as yet, for fear of prejudicing or displeasing others, give you any particular account.

THE other way (Pyrophilus) of making metals afford unobvious colours, is by imbuing divers bodies with solutions of them made in their proper menstruums: as (for instance) though copper plentifully dissolved in aqua fortis, will imbue several bodies with the colour of the solution; yet some other metals will not (as I elsewhere tell you) and have often tried. Gold dissolved in aqua regia will (which is not commonly known) dye the nails and skin, and hafts of knives, and other things made of ivory, not with a golden, but a purple colour, which though it manifest but slowly, is very durable, and scarce ever to be washed out. And if I misremember not, I have already told you in this treatise, that the purer crystals of fine silver made with aqua fortis, though they appear white, will presently dye the skin and nails with a black, or at least a very dark colour, which water will not wash off, as it will ordinary ink from the same parts. And divers other bodies may the same way be dyed, some of a black, and others of a blackish colour.

AND as metalline, so likewise mineral solutions may produce colours differing enough from those of the liquors themselves. I shall not fetch an example of this, from what we daily see happen in the powdering of beef, which by the brine employed about it (especially if the flesh be over-salted) does oftentimes appear at our tables of a green, and sometimes of a reddish colour (deep enough;) nor shall I insist on the practice of some that deal in salt-petre, who (as I suspected, and as themselves acknowledged to me) do, with the mixture of a certain proportion of that, and common salt, give a fine redness, not only to neats tongues, but, which is more pretty as well as difficult, to such flesh, as would otherwise be purely white: these examples, I say, I shall decline insisting on, as chusing rather to tell you, that I have several times tried, that a solution of the sulphur of vitriol, or even of common sulphur, though the liquor appeared clear enough, would immediately tinge a piece of new coin, or other clean silver, sometimes with a golden, sometimes with a deeper and more reddish colour, according to the strength of the solution, and the quantity of it, that chanced to adhere to the metal; which may take off your wonder, that the water of the hot spring at Bath, abounding with dissolved substances of a very sulphureous nature, should for a while as it were gild the new or clean pieces of silver coin, that are for a due time immersed in it. And to these may be added those formerly mentioned examples of the adventitious colours of mineral bodies: which brings into my mind, that even vegetable liquors, whether by degeneration, or by altering the texture of the body that imbibes them, may stain other bodies with colours differing enough from their own, of which very good herbarists have afforded us a notable example, by affirming, that the juice of alcanna being green (in which state I could never here procure it) does yet dye the skin and nails of a lasting red. But I see this treatise is like to prove too bulky, without the addition of further instances of this nature.

MEETING the other day, Pyrophilus, in an Italian book, that treats of other matters, with a way of prearing what the author calls a lacca of vegetables, by which the Italians mean a kind extract fit for painting, like that rich lacca in English commonly called lake, which is employed by painters as a glorious red: and finding the experiment not to be inconsiderable, and very defectively let down; it will not be amiss to acquaint you with what some trials have informed us, in reference to this experiment, which both by our Italian author, and by divers of his countrymen, is looked upon as no trifling secret.

TAKE then the root called in Latin Curcuma, and in English turmerick (which I made use of, because it was then at hand, and is among vegetables fit for that purpose one of the most easiest to be had): and when it is beaten, put what quantity of it you please into fair water, adding to every pound of water about a spoonful or better of as strong a lixivium or solution of pot ashes as you can well make, clarifying it by filtration before you put it to the decocting water. Let these things boil, or rather simmer over a soft fire in a clean glazed earthen vessel, till you find by the immersion of a sheet of white paper (or by some other way of trial) that the liquor is sufficiently impregnated with the golden tincture of the turmeric; then take the decoction off the fire, and filter or strain it, that it may be clean; and leisurely dropping into it a strong solution of roch-allom, you thall find the decoction as it were curdled, and the tincted part of it either to emerge, to subside, or to swim up and down, like little yellow flakes: and if you pour this mixture into a tunnel lined with cap-paper, the liquor, that filtred formerly so yellow, will now pass clean through the filtre, leaving its tincted and as it were curdled parts in the filter, upon which fair water must be so often poured, till you have dulcified the matter therein contained, the sign of which dulcification is (you know) when the water, that has passed through it, comes from it as tasteless as it was poured on it. And if without filtration you would gather together the flakes of this vegetable lake, you must pour a great quantity of fair water upon the decoction after the affusion of the alluminous solution, and you shall find the liquor to grow clearer, and the lake to settle together at the bottom, or emerge to the top of the water; though sometimes having not poured out a sufficient quantity of fair water, we have observed the lake partly to subside, and partly to emerge, leaving all the middle of the liquor clear. But to make this lake fit for use, it must, by repeated affusions of fresh water, be dulcified from the adhering salts, as well as that separated by filtration, and be spread and suffered to dry leisurely upon pieces of cloth, with brown paper, or chalk, or bricks under them to imbibe the moisture *.

* The curious reader that desires further information concerning lakes, may resort to the 7th Book of Neri's art of glass, Englished, (6 or 7 years since the writing of this 49th experiment) and illusrated with learned observations by the inquisitive and experienced Dr. Char1es Merret.

WHEREAS it is presumed, that the magistery of vegetables obtained this way consists but of the more soluble and coloured parts of the plants that afford it, I must take the liberty to question the supposition; and for my so doing, I shall give you this account.

ACCORDING to the notions (such as they were) that I had concerning salts; allom, though to sense a homogeneous body, ought not to be reckoned among true salts, but to be itself looked upon as a kind of magistery, in regard that as native vitriol (for such I have had) contains both a saline substance and a metal, whether copper, or iron, corroded by it, and associated with it; so allom, which may be of so near a kin to vitriol, that in some places of England (as we are assured by good authority the same stone will sometimes afford both) seems manifestly to contain a peculiar kind of acid spirit, generated in the bowels of the earth, and some kind of stony matter dissolved by it. And though in making our ordinary allom the workmen use the ashes of a sea-weed (vulgarly called kelp) and urine; yet those, that should know, inform us, that here in England, there is besides the factitious allom, allom made by nature without the help of those additaments. Now, Pyrophilus, when I consider this composition of allom, and that alcalizate salts are wont to precipitate what acid salts have dissolved, I could not but be prone to suspect, that the curdled matter, which is called the magistery of vegetables, may have in it no inconsiderable proportion of a stony substance precipitated out of the allom by the lixivium, wherein the vegetable had been decocted. And to shew you, that there is no necessity, that all the curdled substance must belong to the vegetable, I shall add, that I took a strong solution of allom, and having filtred it, by pouring in a convenient quantity of a strong solution of pot-ashes, I presently, as I expected, turned the mixture into a kind of white curds, which being put to filtre, the paper retained a stony calx, copious enough, very white, and which seemed to be of a mineral nature, both by some other signs and this, that little bits of it being put upon a live coal, which was gently blown whilst they were on it, they did neither melt nor fly away, and you may keep a quantity of this white substance for a good while (nay, for aught I can guess, for a very long one) in a red hot crucible, without losing or spoiling it; nor did hot water, wherein I purposely kept another parcel of such calx, seem to do any more than wash away the looser adhering salts from the stony substance, which therefore seemed unlikely to be separable by ablutions (though reiterated) from the precipitated parts of the vegetable, whose lake is intended. And to shew you, that there is likewise in allom. a body, with which the fixed salt of the alcalizate solution will concoagutate into a saline substance differing from either of them, I shall add, that I have taken pleasure to recover out of the slowly exhaled liquor, that passed through the filtre, and left the aforementioned calx behind, a body, that at least, seemed a salt very pretty to look on, as being very white, and consisting of an innumerable company of exceeding slender and shining particles, which would in part easily melt at the flame of a candle, and in part fly away with some little noise. But of this substance, and its odd qualities, more, perhaps, elsewhere; for now I shall only take notice to you, that I have likewise with urinous salts, such as the spirit of sal armoniac, as well as with the spirit of urine itself, nay (if I much mistake not) even with stale urine undistilled, easily precipitated such a white calx, as I was formerly speaking of, out of a limpid solution of allom: so that there is need of circumspection in judging of the natures of liquors by precipitations, wherein allom intervenes; else we may sometimes mistakingly imagine, that to be precipitated out of a liquor by allom, which is rather precipitated out of allom by the liquor. And this puts me in mind to tell you, that it is not unpleasant to behold, how quickly the solution of allom (or injected lumps of allom) does occasion the severing of the coloured parts of the decoction from the liquor, that seemed to have so perfectly imbibed them.

THE above-mentioned way of making lakes we have tried not only with turmeric, but also with madder, which yielded us a red lake; and with rue, which afforded us an extract, of (almost, if not altogether) the same colour with that of the leaves.

BUT in regard that it is principally the alcalizate salt of the pot-ashes, which enables the water to extract so powerfully the tincture of the decocted vegetables, I fear, that our author may be mistaken, by supposing, that the decoction will always be of the very same colour with the vegetable it is made of. For lixiviate salts, to which pot-ashes eminently belong, though by piercing and opening the bodies of vegetables, they prepare and dispose them to part readily with their tincture; yet some tinctures they do not only draw out, but likewise alter them, as may be easily made appear by many of the experiments already set down in this treatise. And though allom being of an acid nature, its solutions may in some cases destroy the adventitious colours produced by the alcali, and restore the former; yet besides that allom is not, as I have lately shown, a mere acid salt, but a mixt body; and besides that its operations are languid in comparison of the activity of salts freed by distillation, or by incineration and dissolution, from the most of their earthy parts, we have seen already examples that in divers cases an acid salt will not restore a vegetable substance to the colour, of which an alcalizate one had deprived it, but makes it assume a third very differing from both; as we formerly told you, that if syrup of violets were by an alcali turned green (which colour, as I have tried, may be the same way produced in the violet-leaves themselves without any relation to a syrup) an acid salt would not make it blue again, but red. And though I have, by this way of making lakes, made magistries (for such they seem to be) of brazil, and as I remember of cochineal itself, and of other things, red, yellow, or green, which lakes were ennobled with a rich colour, and others had no bad one; yet in some the colour of the lake seemed rather inferior than otherwise to that of the plant, and in others it seemed both very differing, and much worse. But writing this in a time and place, where I cannot provide myself of flowers and other vegetables to prosecute such trials in a competent variety of subjects, I am content not to be positive in delivering a judgment of this way of lakes, till experience, or you, Pyrophilus, shall have afforded me a fuller and more particular information.

AND on this occasion, Pyrophilus, I must here (having forgot to do it sooner) advertise you, once for all, that having written several of the foregoing experiments, not only in haste, but at seasons of the year, and in places wherein I could not furnish myself with such instruments, and such a variety of materials, as the design of giving you an introduction into the history of colours required; it can scarce be otherwise, but that divers of the experiments, that I have set down, may afford you some matter of new trials, if you think fit to supply the deficiencies of some of them (especially the freshly mentioned about lakes, and those that concern emphatical colours) which deficiencies., for want of being befriended with accommodations, I could better discern than avoid.

THE use of allom is very great as well as familiar in the dyers trade, and I have not been ill pleased with the use I have been able to make of it, in preparing other pigments than those they employ with vegetable juices. But the lucriferous practices of dyers and other tradesmen I do, for reasons that you may know when you please, purposely forbear in this essay, though not strictly from pointing at, yet from making it a part of my present work explicitly and circumstantially to deliver; especially since I now find (though late, and not without some blushes at my prolixity) that what I intended but for a short essay, is already swelled into almost a volume.

YET here, Pyrophilus, I must take leave to insert an experiment, though perhaps you will think its coming in here an intrusion: for I confess its more proper place would have been among those experiments, that were brought as proofs and applications of our notions concerning the differences of salts: but not having remembered to insert it in its fittest place, I had rather take notice of it in this, than leave it quite unmentioned: partly, because it doth somewhat differ from the rest of our experiments about colours, in the way whereby it is made; and partly because the grounds, upon which I devised it, may hint to you somewhat of the method I use in defining and varying experiments about colours. And upon this account I shall inform you, not only what I did, but why I did it.

I CONSIDERED then, that the work of the former experiments was either to change the colour of a body into another, or quite to destroy it, without giving it a successor; but I had a mind to give you also a way, whereby to turn a body endued with one colour into two bodies, of colours as well as consistencies, very distinct from each other, and that by the help of a body that had itself no colour at all. In order to this, I remembered, that finding the acidity of spirit of vinegar to be wholly destroyed by its working upon minium (or calcined lead) whereby the saline particles of the menstruum have their taste and nature quite altered, I had, among other conjectures I had built upon that change, rightly concluded, that the solution of lead in spirit of vinegar would alter the colour of the juices and infusions of several plants, much after the like manner that I had found oil of tartar to do; and accordingly I was quickly satisfied upon trial, that the infusion of rose-leaves would, by a small quantity of this solution well mingled with it, be immediately turned into a somewhat sad green.

AND further, I had often found, that oil of vitriol, though a potently acid menstruum, will yet precipitate many bodies, both mineral and others, dissolved not only in aqua fortis (as some chymists have observed) but particularly in spirit of vinegar. And I have further found, that the calces or powders precipitated by this liquor were usually fair and white.

LAYING these things together, it was not difficult to conclude, that if, upon a good tincture of red rose-leaves made with fair water, I dropped a pretty quantity of a strong and sweet solution of minium, the liquor would be turned into the like muddy green substance, as I have formerly intimated to you, that oil of tartar would reduce it to; and that if then I added a convenient quantity of good oil of vitriol, this last named liquor would have two distinct operations upon the mixture; the one, that it would precipitate that resolved lead in the form of a white powder; the other, that it would clarify the muddy mixture, and both restore and exceedingly heighten the redness of the infusion of roses, which was the most copious ingredient of the green composition. And accordingly trying the experiment in a wine-glass sharp at the bottom (like an inverted cone) that the subsiding power might seem to take up the more room, and be the more conspicuous, I found, that when I had shaken the green mixture, that the coloured liquor might be the more equally dispersed, a few drops of the rectified oil of vitriol did presently turn the opacous liquor into one that was clear and red, almost like a ruby, and threw down good store of a powder, which, when it was settled, would have appeared very white, if some interspersed particles of the red liquor had not a little allayed the purity, though not blemished. the beauty of the colour. And to shew you, Pyrophilus, that there effects do not flow from the oil of vitriol, as it is such, but as it is a strongly acid menstruum, that has the property both to precipitate lead, as well as some other concretes out of spirit of vinegar, and to heighten the colour of red rose-leaves; I add, that I have done the same thing, though perhaps not quite so well, with spirit of salt; and that I could not do it with aqua fortis, because though that potent menstruum does, as well as the others, heighten the redness of roses, yet it would not, like them, precipitate lead out of spirit of vinegar, but would rather have dissolved it, if it had not found, it dissolved already.

AND as by this way we have produced a red liquor, and a white precipitate out of a dirty green magistery of rose-leaves; so by the same method, you may produce a fair yellow, and sometimes a red liquor, and the like precipitate, out of an infusion of a curious purple colour. For you may call to mind, that in the annotation upon the 39th experiment I intimated to you, that had with a few drops of an alcali turned the infusion of logwood into a lovely purple. Now if instead of this alcali I substituted a very strong and well filtrated solution of minium, made with spirit of vinegar, and put about half as much of this liquor, as there was of the infusion of logwood (that the mixture might afford a pretty deal of precipitate) the affusion of a convenient proportion of spirit of salt would (if the liquors were well and nimbly stirred together) presently strike down a precipitate like that formerly mentioned, and turn the liquor, that swam above it, for the most part, into a lovely yellow.

BUT for the advancing of this experiment a little further, I considered, that in case I first turned a spoonful of the infusion of logwood purple, by a convenient proportion of the solution of minium, the affusion of spirit of sal-armoniac would precipitate the corpuscles of lead concealed in the solution of minium, and yet not destroy the purple colour of the liquor; whereupon I thus proceeded: I took about a spoonful of the fresh tincture of logwood (for I found, that if it were stale, the experiment would not always succeed) and having put to it a convenient proportion of the solution of minium to turn it into a deep and almost opacous purple, I then dropped in as much spirit of sal armoniac, as I guessed would precipitate about half or more (but not all) of the lead, and immediately stirring the mixture well together, I mingled the precipitated parts with the others, so that they fell to the bottom, partly in the form of a powder, and partly in the form of a curdled substance, that (by reason of the predominancy of the tinged corpuscles over the white) retained, as well as the supernatant liquor, a blueish purple colour sufficiently deep, and then instantly (but yet warily) pouring on a pretty quantity of spirit of salt; the matter first precipitated was, by the above specified figure of the bottom of the glass preserved from being reached by the spirituous salt; which hastily precipitated upon it a new bed (if I may so call it) of white powder, being the remaining corpuscles of the lead, that the urinous spirit had not struck down. So that there appeared in the glass three distinct and very differingly coloured substances; a purple or violet-coloured precipitate at the bottom, a white and carnation (sometimes, a variously coloured) precipitate over that, and at the top of all a transparent liquor of a lovely yellow, or red.

THUS you see, Pyrophilus, that though to some I may have seemed to have lighted on this (50th) experiment by chance, and though others may imagine, that to have excogitated it must have proceeded from some extraordinary insight into the nature of colours; yet indeed the devising of it need not be looked upon as any great matter, especially to one, that is a little versed in the notions I have in these, and other papers hinted concerning, the differences of salts. And perhaps I might add, upon more than conjecture, that these very notions, and some particulars scatteringly delivered in this treatise, being skilfully put together, may suggest divers matters (at least) about colours, that will not be altogether despicable. But those hinted, Pyrophilus, I must now leave such as you to prosecute, having already spent far more time than I intended to allow myself, in acquainting you with particular experiments and observations concerning the changes of colour; to which I might have added many more, but that I hope I may have presented you with a competent number, to make out, in some measure, what I have, at the beginning of this essay, either proposed as my design in this tract, or delivered as my conjectures concerning these matters. And it not being my present design, as I have more than once declared, to deliver any positive hypothesis or solemn theory of colours, but only to furnish you with some experiments towards the framing of such a theory; I shall add nothing to what I have said already, but a request, that you would not be forward to think I have been mistaken in any thing I have delivered as matter of fact concerning the changes of colors, in case you should not, every time you try it, find it exactly to succeed. For besides the contingencies, to which we have elsewhere shewn some other experiments to be obnoxious, the omission or variation of a seemingly inconsiderable circumstance may hinder the success of an experiment, wherein no other fault has been committed. Of which truth I shall only give you that single and almost obvious, but yet illustrious, instance of the art of dying scarlets: for though you should see every ingredient, that is used about it; though I should particularly inform you of the weight of each; and though you should be present at the kindling of the fire, and at the increasing and remitting of it, whenever the degree of heat is to be altered; and though (in a word) you should see every thing done so particularly, that you would scarce harbour the least doubt of your comprehending the whole art; yet if I should not disclose to you, that the vessels, that immediately contain the tinging ingredients, are to be made of or to be lined with tin, you would never be able, by all that I could tell you else (at least, if the famousest and candidest artificers do not strangely delude themselves) to bring your tincture of cochineal to dye a perfect scarlet. So much depends upon the very vessel, wherein the tinging matters are boiled, and so great an influence may an unheeded circumstance have on the success of experiments concerning colours.