PHYSICAL AND LITERARY, 31 



" the weight of th« quantity of the fluid dif- 

 " placed by it. 



V 22. These "Pbcejiomena appeared to me 

 worthy of obfervation here: both becaufe 

 they fliew the fertility of optical principles in 

 leading to the knowledge of things other- 

 ways inacceflible ; and becaufe they exhibit 

 a clear fpeclmen of a repulfive power^ fimilar 

 to that which we fuppofe neceffary for the 

 reflexion of light from the anterior furface 

 of a denfer medium. Nor do I fee how it is 

 poflible to account for the fufpenfion of the 

 drop in the air by comparative attradiions ;" 

 into which fome other appearances of re- 

 pulfion have been, perhaps, not unfuccefs- 

 fuUv, refolved*. 



SECT. IV. 



On the Change which coloured Bodies undergo 

 in different Lights. 



23. Sir Jfaac Ne-wton has abundantly 

 proved, by a variety of arguments, that the 

 ordinary colours of natural bodies arife folely 



from 



* See Jurin on capUlary attraiiion, at the end of Cotfs 

 hydrojiatical Ltiiures^ 



