Part 14

Suppose we therefore AB in the eighth _Figure_ of the sixth _Scheme_, to represent a tinging _Globule_ or particle which has a greater refraction than the liquor in which it is contain’d: Let CD be a part of the pulse of light which is _propagated_ through the containing _medium_; this pulse will be a little stopt or impeded by the _Globule_, and so by that time the pulse is past to EF that part of it which has been impeded by passing through the _Globule_, will get but to LM, and so that pulse which has been _propagated_ through the _Globule_, to wit, LM, NO, PQ, will always come behind the pulses EF, GH, IK, &c.

Next, by reason of the greater impediment in AB, and its _Globular_ Figure, the Rays that pass through it will be dispers’d, and very much scatter’d. Whence CA and DB which before went _direct_ and _parallel_, will after the refraction in AB, _diverge_ and spread by AP, and BQ; so that as the Rays do meet with more and more of these tinging particles in their way, by so much the more will the pulse of light further lagg behind the clearer pulse, or that which has fewer refractions, and thence the deeper will the colour be, and the fainter the light that is trajected through it; for not onely many Rays are reflected from the surfaces of AB, but those Rays that get through it are very much disordered.

By this _Hypothesis_ there is no one experiment of colour that I have yet met with, but may be, I conceive, very rationably solv’d, and perhaps, had I time to examine several particulars requisite to the demonstration of it, I might prove it more than probable, for all the experiments about the changes and mixings of colours related in the Treatise of Colours, published by the _Incomparable_ Mr. _Boyle_, and multitudes of others which I have observ’d, do so easily and naturally flow from those principles, that I am very apt to think it probable, that they own their production to no other _secundary_ cause: As to instance in two or three experiments. In the twentieth Experiment, this _Noble Authour_ has shewn that the deep _bluish purple-colour_ of _Violets_, may be turn’d into a _Green_, by _Alcalizate Salts_, and to a _Red_ by acid; that is, a _Purple_ consists of two colours, a deep _Red_, and a deep _Blue_; when the _Blue_ is diluted, or altered, or destroy’d by _acid Salts_, the _Red_ becomes predominant, but when the _Red_ is diluted by _Alcalizate_, and the _Blue_ heightned, there is generated a _Green_; for of a _Red_ diluted, is made a _Yellow_, and _Yellow_ and _Blue_ make a _Green_.

Now, because the _spurious_ pulses which cause a _Red_ and a _Blue_, do the one follow the clear pulse, and the other precede it, it usually follows, that those _Saline_ refracting bodies which do _dilute_ the colour of the one, do deepen that of the other. And this will be made manifest by almost all kinds of _Purples_, and many sorts of _Greens_, both these colours consisting of mixt colours; for if we suppose A and A in the ninth Figure, to represent two pulses of clear light, which follow each other at a convenient distance, AA, each of which has a _spurious_ pulse preceding it, as BB, which makes a _Blue_, and another following it, as CC, which makes a _Red_, the one caus’d by tinging particles that have a greater refraction, the other by others that have a less refracting quality then the liquor or _Menstruum_ in which these are dissolv’d, whatsoever liquor does so alter the refraction of the one, without altering that of the other part of the ting’d liquor, must needs very much alter the colour of the liquor; for if the refraction of the _dissolvent_ be increas’d, and the refraction of the tinging particles not altered, then will the preceding _spurious_ pulse be shortned or stopt, and not out-run the clear pulse so much; so that BB will become EE, and the _Blue_ be _diluted_, whereas the other _spurious_ pulse which follows will be made to lagg much more, and be further behind AA than before, and CC will become _ff_, and so the _Yellow_ or _Red_ will be heightned.

A _Saline_ liquor therefore, mixt with another ting’d liquor, may alter the colour of it several ways, either by altering the refraction of the liquor in which the colour swims: or secondly by varying the refraction of the coloured particles, by uniting more intimately either with some particular _corpuscles_ of the tinging body, or with all of them, according as it has a _congruity_ to some more especially, or to all alike: or thirdly, by uniting and interweaving it self with some other body that is already joyn’d with the tinging particles, with which substance it may have a _congruity_, though it have very little with the particles themselves: or fourthly, it may alter the colour of a ting’d liquor by dis-joyning certain particles which were before united with the tinging particles, which though they were somewhat _congruous_ to these particles, have yet a greater _congruity_ with the newly _infus’d Saline menstruum_. It may likewise alter the colour by further dissolving the tinging substance into smaller and smaller _particles_, and so _diluting_ the colour; or by uniting several _particles_ together as in precipitations, and so deepning it, and some such other ways, which many experiments and comparisons of differing trials together, might easily inform one of.

From these Principles applied, may be made out all the varieties of colours observable, either in liquors, or any other ting’d bodies, with great ease, and I hope intelligible enough, there being nothing in the _notion_ of colour, or in the suppos’d production, but is very conceivable, and may be possible.

The greatest difficulty that I find against this _Hypothesis_, is, that there seem to be more distinct colours then two, that is, then Yellow and Blue. This Objection is grounded on this reason, that there are several Reds, which _diluted_, make not a Saffron or pale Yellow, and therefore Red, or Scarlet seems to be a third colour distinct from a deep degree of Yellow.

To which I answer, that Saffron affords us a deep Scarlet tincture, which may be _diluted_ into as pale a Yellow as any, either by making a weak solution of the Saffron, by infusing a small parcel of it into a great quantity of liquor, as in spirit of Wine, or else by looking through a very thin quantity of the tincture, and which may be heightn’d into the loveliest Scarlet, by looking through a very thick body of this tincture, or through a thinner parcel of it, which is highly _impregnated_ with the tinging body, by having had a greater quantity of the Saffron dissolv’d in a smaller parcel of the liquor.

Now, though there may be some particles of other tinging bodies that give a lovely Scarlet also, which though _diluted_ never so much with liquor, or looked on through never so thin a parcel of ting’d liquor, will not yet afford a pale Yellow, but onely a kind of faint Red; yet this is no argument but that those ting’d particles may have in them the faintest degree of Yellow, though we may be unable to make them exhibit it; For that power of being _diluted_ depending upon the divisibility of the ting’d body, if I am unable to make the tinging particles so thin as to exhibit that colour, it does not therefore follow, that the thing is impossible to be done; now, the tinging particles of some bodies are of such a nature, that unless there be found some way of comminuting them into less bulks then the liquor does dissolve them into, all the Rays that pass through them must necessarily receive a tincture so deep, as their appropriate refractions and bulks compar’d with the proprieties of the dissolving liquor must necessarily dispose them to empress, which may perhaps be a pretty deep Yellow, or pale Red.

And that this is not _gratis dictum_, I shall add one instance of this kind, wherein the thing is most manifest.

If you take Blue _Smalt_, you shall find, that to afford the deepest Blue, which _cæteris paribus_ has the greatest particles or sands; and if you further divide, or grind those particles on a Grindstone, or _porphyry_ stone, you may by _comminuting_ the sands of it, _dilute_ the Blue into as pale a one as you please, which you cannot do by laying the colour thin; for wheresoever any single particle is, it exhibits as deep a Blue as the whole mass. Now, there are other Blues, which though never so much ground, will not be _diluted_ by grinding, because consisting of very small particles, very deeply ting’d, they cannot by grinding be actually separated into smaller particles then the operation of the fire, or some other dissolving _menstruum_, reduc’d them to already.

Thus all kind of _Metalline_ colours, whether _precipitated_, _sublim’d_, _calcin’d_, or otherwise prepar’d, are hardly chang’d by grinding, as _ultra marine_ is not more _diluted_; nor is _Vermilion_ or _Red-lead_ made of a more faint colour by grinding; for the smallest particles of these which I have view’d with my greatest Magnifying-Glass, if they be well enlightned, appear very deeply ting’d with their peculiar colours; nor, though I have magnified and enlightned the particles exceedingly, could I in many of them, perceive them to be transparent, or to be whole particles, but the smallest specks that I could find among well ground _Vermilion_ and _Red-lead_, seem’d to be a Red mass, compounded of a multitude of less and less motes, which sticking together, compos’d a bulk, not one thousand thousandth part of the smallest visible sand or mote.

And this I find generally in most _Metalline_ colours, that though they consist of parts so exceedingly small, yet are they very deeply ting’d, they being so ponderous, and having such a multitude of terrestrial particles throng’d into a little room; so that ’tis difficult to find any particle transparent or resembling a pretious stone, though not impossible; for I have observ’d divers such shining and resplendent colours intermixt with the particles of _Cinnaber_, both natural and artificial, before it hath been ground and broken or flaw’d into _Vermilion_: As I have also in _Orpiment_, _Red-lead_, and _Bise_, which makes me suppose, that those _metalline_ colours are by grinding, not onely broken and separated actually into smaller pieces, but that they are also flaw’d and brused, whence they, for the most part, become _opacous_, like flaw’d Crystal or Glass, &c. But for _Smalts_ and _verditures_, I have been able with a _Microscope_ to perceive their particles very many of them transparent.

Now, that the others also may be transparent, though they do not appear so to the _Microscope_, may be made probable by this Experiment: that if you take _ammel_ that is almost _opacous_, and grind it very well on a _Porphyry_, or _Serpentine_, the small particles will by reason of their flaws, appear perfectly _opacous_; and that ’tis the flaws that produce this _opacousness_, may be argued from this, that particles of the same _Ammel_ much thicker if unflaw’d will appear somewhat transparent even to the eye; and from this also, that the most transparent and clear Crystal, if heated in the fire, and then suddenly quenched, so that it be all over flaw’d, will appear _opacous_ and white.

And that the particles of _Metalline_ colours are transparent, may be argued yet further from this, that the Crystals, or _Vitriols_ of all Metals, are transparent, which since they consist of _metalline_ as well as _saline_ particles, those _metalline_ ones must be transparent, which is yet further confirm’d from this, that they have for the most part, _appropriate_ colours; so the _vitriol_ of Gold is Yellow; of Copper, Blue, and sometimes Green; of Iron, green; of Tinn and Lead, a pale White; of Silver, a pale Blue, _&._

And next, the _Solution_ of all Metals into _menstruums_ are much the same with the _Vitriols_, or Crystals. It seems therefore very probable, that those colours which are made by the _precipitation_ of those particles out of the _menstruums_ by transparent _precipitating_ liquors should be transparent also. Thus Gold _precipitates_ with _oyl of Tartar_, or _spirit of Urine_ into a brown Yellow, Copper with spirit of _Urine_ into a Mucous blue, which retains its transparency. A solution of sublimate (as the same Illustrious Authour I lately mention’d shews in his 40. Experiment) _precipitates_ with oyl of _Tartar_ _per deliquium_, into an Orange colour’d _precipitate_; nor is it less probable, that the _calcination_ of those _Vitriols_ by the fire, should have their particles transparent: Thus _Saccarum Saturni_, or the _Vitriol of Lead_ by _calcination_ becomes a deep Orange-colour’d _minium_, which is a kind of _precipitation_ by some Salt which proceeds from the fire; common _Vitriol_ _calcin’d_, yields a deep Brown Red, &c.

A third Argument, that the particles of Metals are transparent, is, that being _calcin’d_, and melted with Glass, they tinge the Glass with transparent colours. Thus the _Calx_ of Silver tinges the Glass on which it is anneal’d with a lovely Yellow, or Gold colour, &c.

And that the parts of Metals are transparent, may be farther argued from the transparency of Leaf-gold, which held against the light, both to the naked eye, and the _Microscope_, exhibits a deep Green. And though I have never seen the other Metals _laminated_ so thin, that I was able to perceive them transparent, yet, for Copper and Brass, if we had the same conveniency for _laminating_ them, as we have for Gold, we might, perhaps, through such plates or leaves, find very differing degrees of Blue, or Green; for it seems very probable, that those Rays that rebound from them ting’d, with a deep Yellow, or pale Red, as from Copper, or with a pale Yellow, as from Brass, have past through them; for I cannot conceive how by reflection alone those Rays can receive a tincture, taking any _Hypothesis_ extant.

So that we see there may a sufficient reason be drawn from these instances, why those colours which we are unable to _dilute_ to the palest Yellow, or Blue, or Green, are not therefore to be concluded not to be a deeper degree of them; for supposing we had a great company of small _Globular_ essence Bottles, or round Glass bubbles, about the bigness of a Walnut, fill’d each of them with a very deep mixture of Saffron, and that every one of them did appear of a deep Scarlet colour, and all of them together did _exhibit_ at a distance, a deep dy’d Scarlet body. It does not follow, because after we have come nearer to this _congeries_, or mass, and divided it into its parts, and examining each of its parts severally or apart, we find them to have much the same colour with the whole mats; it does not, I say, therefore follow, that if we could break those _Globules_ smaller, or any other ways come to see a smaller or thinner parcel of the ting’d liquor that fill’d those bubbles, that that ting’d liquor must always appear Red, or of a Scarlet hue, since if Experiment be made, the quite contrary will ensue; for it is capable of being _diluted_ into the palest Yellow.

Now, that I might avoid all the Objections of this kind, by exhibiting an Experiment that might by ocular proof convince those whom other reasons would not prevail with, I provided me a _Prismatical Glass_, made hollow, just in the form of a Wedge, such as is represented in the tenth _Figure_ of the sixth _Scheme_. The two _parallelogram_ sides ABCD, ABEF, which met at a point, were made of the clearest Looking-glass plates well ground and polish’d that I could get; these were joyn’d with hard cement to the _triangular_ sides, BCE, ADF, which were of Wood; the _Parallelogram_ base BCEF, likewise was of Wood joyn’d on to the rest with hard cement, and the whole _Prismatical_ Box was exactly stopt every where, but onely a little hole near the base was left, whereby the Vessel could be fill’d with any liquor, or emptied again at pleasure.

One of these Boxes (for I had two of them) I fill’d with a pretty deep tincture of _Aloes_, drawn onely with fair Water, and then stopt the hole with a piece of Wax, then, by holding this Wedge against the Light, and looking through it, it was obvious enough to see the tincture of the liquor near the edge of the Wedge where it was but very thin, to be a pale but well colour’d Yellow, and further and further from the edge, as the liquor grew thicker and thicker, this tincture appear’d deeper and deeper, so that near the blunt end, which was seven Inches from the edge and three Inches and an half thick; it was of a deep and well colour’d Red. Now, the clearer and purer this tincture be, the more lovely will the deep Scarlet be, and the fouler the tincture be, the more dirty will the Red appear; so that some dirty tinctures have afforded their deepest Red much of the colour of burnt Oker or _Spanish_ brown; others as lovely a colour as _Vermilion_, and some much brighter; but several others, according as the tinctures were worse or more foul, exhibited various kinds of Reds, of very differing degrees.

The other of these Wedges, I fill’d with a most lovely tincture of Copper, drawn from the filings of it, with spirit of _Urine_, and this Wedge held as the former against the Light, afforded all manner of Blues, from the faintest to the deepest, so that I was in good hope by these two, to have produc’d all the varieties of colours imaginable; for I thought by this means to have been able by placing the two _Parallelogram_ sides together, and the edges contrary ways, to have so mov’d them to and fro one by another, as by looking through them in several places, and through several thicknesses, I should have compounded, and consequently have seen all those colours, which by other like compositions of colours would have ensued.

But insteed of meeting with what I look’d for, I met with somewhat more admirable; and that was, that I found my self utterly unable to see through them when placed both together, though they were transparent enough when asunder; and though I could see through twice the thickness, when both of them were fill’d with the same colour’d liquors, whether both with the Yellow, or both with the Blue, yet when one was fill’d with the Yellow, the other with the Blue, and both looked through, they both appear’d dark, onely when the parts near the tops were look’d through, they exhibited Greens, and those of very great variety, as I expected, but the Purples and other colours, I could not by any means make, whether I endeavour’d to look through them both against the Sun, or whether I plac’d them against the hole of a darkned room.

But notwithstanding this mis-ghessing, I proceeded on with my trial in a dark room, and having two holes near one another, I was able, by placing my Wedges against them, to mix the ting’d Rays that past through them, and fell on a sheet of white Paper held at a convenient distance from them as I pleas’d; so that I could make the Paper appear of what colour I would, by varying the thicknesses of the Wedges, and consequently the tincture of the Rays that past through the two holes, and sometimes also by varying the Paper, that is, insteed of a white Paper, holding a gray, or a black piece of Paper.

Whence I experimentally found what I had before imagin’d, that all the varieties of colours imaginable are produc’d from several degrees of these two colours, namely, Yellow and Blue, or the mixture of them with light and darkness, that is, white and black. And all those almost infinite varieties which Limners and Painters are able to make by compounding those several colours they lay on their Shels or _Palads_, are nothing else, but some _compositum_, made up of some one or more, or all of these four.

Now, whereas it may here again be objected, that neither can the Reds be made out of the Yellows, added together, or laid on in greater or less quantity, nor can the Yellows be made out of the Reds though laid never so thin; and as for the addition of White or Black, they do nothing but either whiten or darken the colours to which they are added, and not at all make them of any other kind of colour: as for instance, _Vermilion_, by being temper’d with White Lead, does not at all grow more Yellow, but onely there is made a whiter kind of Red. Nor does Yellow _Oker_, though laid never so thick, produce the colour of _Vermilion_, nor though it be temper’d with Black, does it at all make a Red; nay, though it be temper’d with White, it will not afford a fainter kind of Yellow, such as _masticut_, but onely a whiten’d Yellow; nor will the Blues be _diluted_ or deepned after the manner I speak of, as _Indico_ will never afford so fine a Blue as _Ultramarine_ or _Bise_; nor will it, temper’d with _Vermilion_, ever afford a Green, though each of them be never so much temper’d with white.

To which I answer, that there is a great difference between _diluting_ a colour and whitening of it; for _diluting_ a colour, is to make the colour’d parts more thin, so that the ting’d light, which is made by trajecting those ting’d bodies, does not receive so deep a tincture; but whitening a colour is onely an intermixing of many clear reflections of light among the same ting’d parts; deepning also, and darkning or blacking a colour, are very different; for deepning a colour, is to make the light pass through a greater quantity of the same tinging body; and darkning or blacking a colour, is onely interposing a multitude of dark or black spots among the same ting’d parts, or placing the colour in a more faint light.

First therefore, as to the former of these operations, that is, diluting and deepning, most of the colours us’d by the Limners and Painters are incapable of, to wit, _Vermilion_ and _Red-lead_, and _Oker_, because the ting’d parts are so exceeding small, that the most curious Grindstones we have, are not able to separate them into parts actually divided so small as the ting’d particles are; for looking on the most curiously ground _Vermilion_, and _Oker_, and _Red-lead_, I could perceive that even those small _corpuscles_ of the bodies they left were compounded of many pieces, that is, they seem’d to be small pieces compounded of a multitude of lesser ting’d parts: each piece seeming almost like a piece of Red Glass, or ting’d Crystal all flaw’d; so that unless the Grindstone could actually divide them into smaller pieces then those flaw’d particles were, which compounded that ting’d mote I could see with my _Microscope_, it would be impossible to _dilute_ the colour by grinding, which, because the finest we have will not reach to do in _Vermilion_ or _Oker_, therefore they cannot at all, or very hardly be _diluted_.

Other colours indeed, whose ting’d particles are such as may be made smaller, by grinding their colour, may be _diluted_. Thus several of the Blues may be _diluted_, as _Smalt_ and _Bise_; and _Masticut_, which is Yellow, may be made more faint: And even _Vermilion_ it self may, by too much grinding, be brought to the colour of _Red-lead_, which is but an Orange colour, which is confest by all to be very much upon the Yellow. Now, though perhaps somewhat of this _diluting_ of _Vermilion_ by overmuch grinding may be attributed to the Grindstone, or muller, for that some of their parts may be worn off and mixt with the colour, yet there seems not very much, for I have done it on a Serpentine-stone with a muller made of a Pebble, and yet observ’d the same effect follow.