^ of the colours, one half of the Colours rn^y be mtefcepted by 
a fpoakeor cogg, and the other half pafs through an inter* 
ftice. The Wheel beiog in this pofture, you may firft turn it 
' flowiy aboutj to fee all the colours fall fucceffiv^ely on the 
lame place of the paper, held at their aforefaid concourfe 5 
and if you then accelerate its gyration, until the Confecution 
of thofe coloars be fo quick, that you cannot diftioguifti 
them feverally;the refultiog colour will be a Whiteoefs per- 
fedly like that, which an mn-refracted beam of Light exhibits 
when in like manner rucceffively interrupted by the fpoaksor 
^ CQggs of that circulating Wheel* And that this tvhitenefs i$ 
produced by a fucbeffive Intermixture of the Colours, with- 
out their being aflimilated 5 or reduced to any UnifGr- 
mity, is certainly beyond all doubr^ unlefs things that exifl: 
not at the lame time may notwithftanding ad on one a* 
nother. 
1 here ar^ yet other Circumftances, by which the Truth 
might have been decidedj as by viewing the White conGourfe 
of the Colours through another Prifrae plac'dclofe to the eye, 
by whofe Refraction that whitenels may appear again tranf- 
form'd into Colours : And then, to examine their Origin, if an 
Affiftant intercept any of the colours at the Lens before their 
atrival at the Whitenefs, the lame colours will vanifli from a- 
moDgft thofe, into which that Whitenels is converted by the 
Jecond Prifme* Now, if the rays which difappear be the lame 
with thofe that are intercepted, then it muft be acknowled.- 
ged, that the fecond Prifme makes no new colours in any rays, 
vi^hich were not in thtm before t\it\t concourfe at the paper, 
Which is a plain indication, that the rays of fcvera! colours re- 
main diftinft from one another in the Whitenels, and that from 
ihmpevimsdK^oMom are dcriv'dthe Colours of the (econd 
Prifme. And, by the way, what isfaid of their Colors may be 
applied to their R^frangibility. 
The aforefaid fF/&ee/may be alfohere made ufe of; and, if 
its gyration be neither too quick nor two flow, the fuc- 
ccfsion of the colours may be difccrri'd through the Prifme, 
whilft to the naked eye of a Byftanderthev exhibit white, 
^ueis. 
There is fonietbiDg ftill remaining to be faid ofthis Experi- 
