184 Diamonds, &c. imbibe Light. [Book III. 



in the dark, ice and fnow had this property in a re- 

 cm ark able degree *. 



The light which is emitted from putrid fubftances 

 and rotten wood, alfo that of ignes fatui, and other 

 fimilar meteoi-s, proceeds from a different caufe, and 

 will be explained in another part of this work, to 

 which the fubject more properly appertains. 



To the principle of attraction Newton has alfo re- 

 ferred the molt extraordinary phenomena of light, re- 

 fraction and inflexion. That incomparable philofopher 

 has alfo fhewn that light is not only fubject to the law 

 of attraction, but of repulfion alfo, fince it is repelled 

 or reflected from certain bodies ; a property which 

 was long known, but was never underftood till he gave 

 us a fyftem, which accounts for the general operations 

 of nature, upon fewer and fimpler principles, yet in a 

 manner much more fatisfactory than any which had 

 preceded. But to enumerate and briefly explain thefe 

 general properties would extend this chapter, to an im- 

 proper length, and would probably in fome meafure. 

 tend to confufe the ftudent. 



* Prieftley's Optics, p. 368, 369, 370. 



