Artalyfis of the Air. 3 1 3 



" that the rays of light be bodies of different 

 " fizes, the lead of which may make the 

 " weakeft and darkeft of the colours, and be 

 more eafily diverted, by refra&ing furfaces 

 from the right courfe; and the reft, as 

 they are bigger and bigger, may make the 



ftronger and more lucid colours and be 



more and more difficultly diverted, <%u. 29." 

 So £>u. 30. he obferves of air, " That denfe 

 f£ bodies, by fermentation, rarefy into feveral 

 " forts of air, and this air, by fermentation, 

 cc and fometimes without, returns into denfe 

 11 bodies. " And fince we find in fact from 

 thefe Experiments, that air arifes from a 

 great variety of denfe bodies, both by fire 

 and fermentation, it is probable that they 

 may have very different degrees of elafticity, 

 in proportion to the different fize and denfity 

 of its particles, and the different force with 

 which they were thrown offinco an elaftick 

 ftate. " Thofe particles (as Sir Isaac New- 

 ' c ton obferves) receding from one another, 

 " with the greateft repulfive force, and bein^ 

 u molt difficultly brought together, which 

 " upon contact cohere mofl ftroncrly. " 

 Whence thofe of the weakeft elasticity will 

 be leaft able to refill: a counter-acting power, 

 and will therefore be fooneft changed from 



an 



