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ser In SI«, Flgure, and Agitation, must neceflarily be unequal: Wlfich t»enough to denominate Light an Aggregate of Difform R*)s, according to anyos thoso Hypotheses. And if thofe Original Inequalkies nuy fiiffice to diflfe-rence the Rays in Cosour and Refrangibility, I soe no reason, why they, thatadhere to any os thofe Hypotheses, ihould feek for other Caufes os thele Ef-fects, unlefs (to use the Objector’s Argument) they will multlply Entltic; nithou .*

Kcccffity.

The rhird thing to be confidered is, the Condiüon of the Animadversor SConceliions, which is, That I would explicate my Theories by his Hypothefis.And is Icould comply with him in that point, there wculd belittle or no dif-serenccbetween us. For he Gram?, That, without any respcct to a DifterencIncidencc of Rays, there are Different Refractions ; but he would have it ex-plicated, nor by the different Refrangibility ot lc-veral Raysybut by the Spütiugand Rarefying ot /Ethcreal Pulses. He grants my third, fourth, and sixtliPropofitions; the sense of which is, That Uncompounded Colours are Unc'nan-geable, and that Compounded ones are-Changeable only by resolving themintothe Colours, of which they are Compounded ; and that all the Changes,which can be wrought in Colours, are effected only by varioufly mixing ovparting them : But he grants them on Condition, that I will explicate Co-lotirs by the two lides of a Split Pulse, and so malte but two Species of them,accounting all other Colours in the World to be but variousDegrees and Di-lutings of thole two. And he further grants, that Whitenels is produe’d bythe Convention of all Colours; but then I muit allow it to be not only byMixture of thofe Colours, but by a farther Uniting of the Parts of the Ray-fupposcd to bc sormerly Split.

lf I would procecd to examine diele his Explications, I think it would beno difficult matter to fliew, that they are not only Insiifficient, but in somerespects to me (at leastj Unintelligible. For though it be easie to conceive,how Motion may be dilated, and spread, or how parallel Motions may be-come Diverging ; yet I understood not, by what Artifice any Linear Motioncan by a RefracVmg Superficies be infinitely dilated and rarefied, so as to be-come Supcrficial: Or, if that be fupposod, yet 1 underffand as little, whyicshould be split at so small an Angle only, and not rathet spread and dispersed-through the whole Angle of Rerraction. And further, though 1 can easilyimagine, how Unlike Motions nuy erosi one another; yet I cannot well con-ceive, how they should coalesce into one Uniform Motion, and then partagain, and rccover the former Unlikenesi; norwithstanding tliat I conjecturethe ways, by which the Animadversor may endeavour to explain it. So thatthe Direct, Uniform, and llndithirb’d Pulses should be Split and Dilturbed byRefraction j and yet the Oblique and Disturbed Pulses persist without Splittingor further dillurbance by foUotving Refractions, is (to me) as unintelligible,and there isasgreat a didiculty in the Nuntber of Colours j as you will soehereafter.

But whatever be the Advantages or Disadvantages of this Hypothcsis, Ihope I may be cxcusod from takiag it up, since 1 do not think it needful toexplicate my Doctrine by any Hypothelis at all. For if Light be confidered

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