Now, that this may be the better understood, I shall endeavour to 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.
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.