To proceed therefore; I suppose, that all transparent colour’d bodies, whether fluid or solid, do consist at least of two parts, or two kinds of substances, the one of a substance of a somewhat differing refraction from the other. That one of these substances which may be call’d the tinging substance, does consist of distinct parts, or particles of a determinate bigness which are disseminated, or dispers’d all over the other: That these particles, if the body be equally and uniformly colour’d, are evenly rang’d and dispers’d over the other contiguous body; That where the body is deepest ting’d, there these particles are rang’d thickest, and where ’tis but faintly ting’d, they are rang’d much thinner, but uniformly. That by the mixture of another body that unites with either of these, which has a differing refraction from either of the other, quite differing effects will be produc’d, that is, the consecutions of the confus’d pulses will be much of another kind, and consequently produce other sensations and phantasms of colours, and from a Red may turn to a Blue, or from a Blue to a Red, &c.

Now, that this may be the better understood, I shall endeavour to [Schem. 6.]
Fig. 7. explain my meaning a little more sensible by a Scheme: Suppose we therefore in the seventh Figure of the sixth Scheme, that ABCD represents a Vessel holding a ting’d liquor, let IIIII, &c. be the clear liquor, and let the tinging body that is mixt with it be EE, &c. FF, &c. GG, &c. HH, &c. whose particles (whether round, or some other determinate Figure is little to our purpose) are first of a determinate and equal bulk. Next, they are rang’d into the form of Quincunx, or Equilaterotriangular order, which that probably they are so, and why they are so, I shall elsewhere endeavour to shew. Thirdly, they are of such a nature, as does either more easily or more difficultly transmit the Rays of light then the liquor; if more easily, a Blue is generated, and if more difficultly, a Red or Scarlet.

And first, let us suppose the tinging particles to be of a substance that does more impede the Rays of light, we shall find that the pulse or wave of light mov’d from AD to BC, will proceed on, through the containing medium by the pulses or waves KK, LL, MM, NN, OO; but because several of these Rays that go to the constitution of these pulses will be slugged or stopped by the tinging particles E, F, G, H; therefore there shall be secundary and weak pulse that shall follow the Ray, namely PP which will be the weaker: first, because it has suffer’d many refractions in the impeding body; next, for that the Rays will be a little dispers’d or confus’d by reason of the refraction in each of the particles, whether round or angular; and this will be more evident, if we a little more closely examine any one particular tinging Globule.

[Schem. 6.]
Fig. 8.

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.