t 107 ] 



XX IT. Tnqiimcs into Coloured Light, hj a Colhiiion of the 

 Expcnmcnis and Obfcrvations made by Sir Ijaac Newton 

 on that Suhjcd ; together luith June add'uhnal ones. By 

 Governor Y'ow^ ALL. 



T, 



[Concluded from p. 49.] 



HE green prlfniatic tint is fuppofed to be homogeneous, 

 becaulf coniiiliutr of angles of refran^ibility in the yellow and 

 In the blue fo exaclly conueAetl in clegree at the point where 

 they coiilefce, thai no prifm nor any fucceHion ot prilnis have 

 as yet decompofed it. It is, however, in various other in- 

 ftances decompofed ; in the circles of colours arifing from 

 the refractions of lliiht paffing between two lenses, as alfo in 

 the rings of colours exhibited on bubbles of water. In thefe 

 inftauccs its conftituent parts, which combined form the 

 compoLmd green, emerge as yellow on one lide and blue on 

 the other. 



Sir Ifaac Newton, in Obferv. iv. part i. book 2. marking 

 the order of colours in the circles produced by the refrac- 

 tion of light between two lenses, fays, " the green was very 

 copious and lively, inclining on one fide to blue, on the other 

 to yellow:" and' again, in part ii. book 2. p. 202. he fays, 

 ^* the green exhibued is principally conftituted of original 

 gr£en,h\.\l not without a mixture of blue and yellow:" again^ 

 in part i. book 2. p. 190. he fays, " then after a lively oraneft 

 followed an intenj'e bright and copious yellow, which was alio 

 the beft of all the vellows ; this changed firtl; to a greenifll 

 yellow, then to a greeniili blue ; but the green between the 

 yellow and the blue was very little and dilute, fceniing ra- 

 ther a irreenijh ivhite than a green : the blue which fucccedci 

 became verv good." In this obfervation made on the rings 

 of colours on bubbles, notice the incrcaling intenfenefs of 

 thelitiht; alfo fuccclfive gradations; alfo the gradual pro- 

 -cefs oT the compofition of green and of its decompofition, 

 which is given in the next obfervation, p. 189: " After the 

 red fucceedt'd lillle or no yellow, but a c(;pious green, wh.ioh 

 at firlt inclined a little to yellow, then became a prettv briflc 

 and f^ood ivi/loiu-grcen, and afterward.^ changed to a bhuifh 

 colour ; but there fucrteedcd neiilier blue nor violet." In the 

 firll inlhuice, the very little and dilute greemfli while, as well 

 as the willow-green m the fecond, was the di)minancy of an 

 intervcninrr while, as will come out hercr\fier ; and in both 

 inftances the yellf)wi(h green and blueifh green mark iha 

 coiiipouiid, partaking on each fide of the yellow or of the 



bluf. 



