C 5090 > 
there would be Iktleorno difference between Us. For he f 
grants, that without any refpecc to a different Incidence of 
rays there arc different Refraftions ^ but he would have it ex- 
plicated, not by the different Refrangibility of feveralRays, 
but by the Splitting and Rarefying of asthercal pulfes. He 
grants my third, Jourth and fixth Fropoficions ; the (enfe of 
which is. That Unxompounded Colors are unchangeable^and 
that Compounded ones are changeable only by refolving them 
into the colorSj of which they are compounded; and that all 
the Changes, which can be wrought in Colours, are effccSted 
only by varioufly mixing or parting them: But he grants them 
on condition tha t I will explicate Colors by the two fides of a 
fphtpulfe, and fo make but two /pedes of them, accounting 
all other Colors in the world to be but various degrees and di- 
lutings of thofetwo. And he further grants, that IVhiteneffe is 
produced by tbe Convention of all Colors; but then I muft al* 
low it to be not only by Mixture of^bfe Colors, but by a far- 
ther Uniting of the parts of the Ray fuppofed to be formerly 
fph't. 
If I would proceed to examine thefe his Explications, I 
tbink it would be no difficult matter to fhew, that they are not 
only infufficient^hnt in fome refpectsto me Cat leaft) un-inteBr^ 
gible^ For, though it be eafie to conceive, how Motion may be 
dilated and fpread;, or how parallel motions may become di- 
verging 5 yet I underftand not, by what artifice any Linear 
motion can by a refracting fuperficies be infinitely dilated and 
farefied, (b as to become Superficial : Or, if that be fuppofed, 
yet I underftand as little, why it fliould be fplit at fo fmall an 
angle only, and not rather fpread and difperfed through the 
whole angle of Refraction. And further, though I can eafily 
imagine, how Unlike motions may crofs one another 5 yet I 
cannot well eonceive,how;they Cbould coalefce into one uniform 
motion, and then part again, and recover their former Un- 
likenefs 5 notwithftanding that I conjecture the ways,by which 
tl^e Animadvfrfor Iflay endeavour to explain it. So that the V>u 
rect, uniform and undifturbed Pulfes ihould be fplit anddi- 
ftiirbed by Refraction 4 and yet the Oblique and difturbed 
Pulfes perfift without fplitting or further difturbance by fol- 
lowing Refractions, is (to me) as uriintelligible. And there i$ 
as I 
