the various circumftances* One circumftanoe I there decFa- 
xed^ of whichlfeenoDOtice taken* anditisj That if any cos 
lour at the Lem be intercepted, the Whitenefs will be changed 
into the other colours • if all the colours but red he intercep- 
ted, that Red alone in the coucourfe or crofEng of the Rays 
will not confticute Whitenefs, but continues as much Red as 
before; and fo of the other colours. So that the bufinefs is^ 
not only to Ihew^ how rays^ which before theconcourfe ethu 
bit colours, do in the concourfe exhibit White $ but to ikcw^ 
How in the fame place, where the feveral forts of rays aparc^ 
exhibit (everal colourSja Gonfufion of all together makcWhite, 
For inftance, if red alone be firft tranfmitted to tbe paper at 
the place of concourle, and then the other colours be let hll 
on that Red, the ^efiion will be. Whether they convert it in * 
t> White, by mixing with it only, as Blew falling ori Yell6w 
light is fuppos'd to compound Green 5 or. Whether there be 
fome further change wrought in the colours by their mutual : 
a^ing on one another, untill, like contrary Peripatetic qadb 
ties, they become ailimilated. And he that (hall explicate this 
lafl C?^^ mecbanicali}^ mufl: conquer a double impofBbility. 
He muft/^ fliew, that many unlike motions in a Fluid can by 
dafliing io a6ir on one another, and change each other, as to 
become one Uniform motion i and theti^ that an Uniform mo- 
tion can of it felf, without any new unequal imprefBons, de- 
part into a great variety of motions regularly un-equal. And 
after this he muft further tell me, Why all objedts appear 
not of the fame colour, that is, why their colours in the Air^ 
where the rays that convey them everyway are confufedly 
mixt, do not aiEmilate one another and become Uniform be- 
fore they arrive at the Spedlators eye f 
But if there be yet any doubting,*tis better to put the Event 
on further Circumftancei of the Experiment^ th^n to acquiefce 
in the poffibility of any Hypothetical Explication, As, for in- 
fiance, by trying^What will be the apparition of thefe colours 
in a very quick Confecution of one another. And this may be 
eafily pertorm'd by the rapid gyration of a Wheel with fmany 
Spoaks or coggs in its penmeter, whofe loterltices and thick* 
neffes may be equal and of fuch a largeneQ^ that, if the Wheel 
fee interpoled between the Prifme and the whire concourfe 
