q6 
C 5084 ) 
6f the colours, one half of the Colours may be intercepted bf 
a fpoake or cogg, and the other half pafs through an inter* 
ftice. The Wheel being in this pofture, you may firft turn it 
flowly aboutj to fee all the colours fall focceffively on the 
lame place ofthepaper^ held at their aforefaid concourfe 5 
and if you then accelerate its gyration, until the Confecutiou 
of thofe colours be fo quick, that you cannot diftinguilh 
them feverally, the refulting colour will be a Whitenefs per- 
fedly like that, which an an-refracted beam of Light exhibits, 
when in like manner fucceffivcly interrupted by the (poaks or 
coggs of that circulating Wheel* And that this WhiUneft is 
produced by a fucceffive Intermixture of the Colours, with- 
out their being affimilated , or reduced to any Unifor- 
mity, is ccrtaioly beyond all doubr, unlefs things that exift 
not at the lame time may notwithftanding aft on one a» 
nother. 
There are yet other Circumftances, by which the Truth 
might have been decided^ as by viewing the White concourfe 
of the Colours through another Prifme ptac d clofe 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 
arrival at the Whitenefs, the fame colours will vanifh from a- 
moDgft thofe^ into which that Whitenefs is converted by the 
Jecond Prifme* Now, if the rays which difappear be the fame 
with thofe that are intercepted, then it muft be acknowlei 
ged, that the fecond Prifme makes no new colours in any rays, . 
which were not in them before their concourfe at the paper* 
Which is a plain indication, that the rays of fevcral colours re- 
main diftinft from one another in the Whitenefs, and that frotn 
ihtiTpevious difpofitioos are dcriv'd tne Colours of the (econd 
Prifme. Andjby the way, what is faid of their Colors may be 
applied to their Refrangibility. 
The aforefaid Wheel m^^ be alfohere made ufe of 3 and, if 
its gyration be neither too quick nor two flow, the fuc- 
cefsion of the colours may be difcern'd through the Prifine, 
whilfi to the naked eye of a Byftander they exhibit white^ 
There is fomething ftill remaining to be faid of this Experi. 
ment 
