Mifiellanm Curiofa. 1 1 5 



be conceived to flow fuccemvely from the Sun, 

 F P, and F f{ two of thofe Rays unequally re- 

 fracted, which the Lens makes to converge to- ^ 

 wards Q, and after decuffation to diverge again. 

 And H I the Paper, at divers diftances, on 

 which the Colours are projected, which in 

 conftitute PVbitenefs, but are Red and Tellow in 

 y, and f, and Blue and Purple m P, />, and t. 



If you proceed further to try the inipofTbiHty 

 of changing any uncompounded Colour (which' 

 I have afferted in the third and thirteenth Pro- 

 portions,,) 'tis requilite that the Room may be 

 very dark, left any fcattering light, mixing with 

 the Colour, diiturb and allay it, and render it 

 compound, contrary to the defign of the Experi- 

 ment. 'Tis alio requifite, that there be a per- 

 fecter feparation of the Colours, than, after the 

 manner above defcribed, can be made by the 

 Refraction of one fingle Prifm ; and how to make 

 fuch farther feparations, will fcarce be difficult to 

 them, that conlider the difcovered Laws of Re- 

 fractions. But if trial (hail be made with Co- 

 lours not throughly feparated, there muft be al- 

 lowed changes proportionable to the mixture. 

 Thus if compound Yellow Light fall upon blue 

 Bife, the Bife will not appear perfectly yellow, 

 but rather green, becaufe there are in the yelloto 

 mixture many Rays indued with green, and green 

 being lels remote from the ufual blue Colour of 

 Bue than yellow, is the more . copioufly reflected 

 .by it. 



In like manner, if any one of the Prifaatick 

 Colours, fuppofe red, be intercepted, on defign 

 to try the afferted impoffibility of reproducing 

 /that Colour out of the others which are preter* 

 mitted ; 'tis neceflary, either that the Colours 

 be very well parted before the red be intercep- 



I ted 5 



