Permanent Colours of Opake Bodies. 241 

 violet, exhibit a green colour by refledled light. * 

 Thefe he calls oppofue colours, by which'^terrn 

 he ufually exprefTes thofe tranfmitted colours 

 which are feen in the part of the medium, which 

 IS oppofite to the refieded colours, and vice 

 verja. f 



All colours, tranfmitted by femipellucid fub- 

 flances, are oppofite to thofe which the fubftances 

 exhibit when viewed by incident light. And in 

 proportion as Tranfparent Coloured Media grow 

 opake, by the formation, or reception, of wliite, 

 or colourlefs particles, the colours which they 

 tranfmic recede farther and farther from the 

 original colour, which the medium tranfmitted 

 whilft it was tranfparent, until at lafl: the mafs 

 grows fo opake, that no rays are any longer 

 tranfmitted. 



I.fhall not enter upon any farther explanation 

 of the manner in which the water of the fea ads 

 upon the rays of light, as the obfervations which 

 have been made refpeding the air, and other 

 femipellucid media, are likewife applicable to 

 the optical appearances of the fea. 



The femipellucid fubftances, which I have 

 hitherto defcribed, refleft the more refrangible, 



and 



•lb. Prop. V. Theor. IV. Exp. X. <' If the red and 

 v.olet be intercepted, the remaining yellow, green and 

 blue, wiJl compound a green." 



lb. L. II. Part. I. Obf. IX. '« By looking throu;ih 



»» twin y%^_.:.^ l'r^.~ _- ° _0 



inter- 

 jacent 



the two contiguous objeft glafles, I found that the inter- 

 V 01,. Ji, p 



