( '59 )

of White wotild befb far from contradicting, that ir Would rather illustrateand confirm my Theory; becaufe by the dinerence of that from other Whitesk would appear, that other Whites are not Compounded ofonly two Colourssike that. Andtherefore if Monsieur N. would prove any thing, it is requi-site that he do not only produce out of two Primitive Colours a White, whichto the naked Eye {hall appear like other Whites, but also (hall agree with themin all other Properties.

But to let you widerstand, wherein stich a White would differ front other -WItites, and why from thence it would follow that other W'hires are other-wiso Compotmded, I stall lay down this Position.

T hat a Compounded Colour ennbe resohed into no more simple Colours than tl.oftqf which it is Compounded.

This seems to be solf evident, and I have also rryed it leveral ways, andparticularly by this which foilows. Let «t rcprelent an Oblong piece of WhitePaper about \ or | of an inch broad, and illuminatcd in v a Dark Room, witha Mixture of two Colours cast upon it from two Prifins', soppose a deep Blueand Scarlet, which rauft ßverally be as Uricompounded as rhey can conveni-ently be made. Then, ata convenient distance, sopposeof stx or eight Yards,view it through a clear triangulär Glast or Crystal Prism hcld parallel to thePaper, and you stall see the two Colours parted from one another in the fasti-ori of two Images of the Paper, as they are rcprelentcd at ß and y, wheresoppose ß the Scarier, and y the Blue, without Green or any other Colourbetween thetm-i

Nöw from the'aforestid Position I deduce these two Conclusions. 1. Thatstthere were found out a way to Compound White ot two Simple Colours only,that White would be again resolvable into no more than two. i. That ifother Whites, as tharof the Sun’s Light, &c. be resolvable into more thantwo simple Colours fas I> find by Experiment that they are) then they mustbeCompounded of more than two.

To malte this planier", suppose that A represents a Wl.ite Body, illuniina-ted by a direct Beam of the Sun tranfmitted through a (mali i Iole into a darkRoom, and <t stich another Body, illumiriäted by a .Mixture of two simpleColours, which, if postibit niay malte it also appear of a White Colour ex-afctly like A. Then, at a convenient distance, view these two Whites thro’ aPristi, and A will bechanged into a Series of all Colours, Red, Yellow,Green, Blue, Purple, with their intermediäre degrees socceeding in order,sfom B to C. But -t, according tö the' asorefaid Experiment, will ’onlyyield those two Colours of which it was Compounded, and those. not con-terminate like the Colours at B C, but' separate from one another, as at ß ' ■and y, by means of the different Refrangibility of the Rays to which- theybelong. And thus by comparing these two Whites, they would appear to beofla different Cortstitution, and'Ä to consist of more Colours than *. So thatwhat Monsieur N. comends ffors Would 1 rathet advance my Theory by the ac-eeft of a new kindof White, than conclude agakist it. Bitt 1 see nu hope»,

•f Comppunding steh a Whites

Aa-»