Chap. 5.] Phenomena of Valour. . ij^ 



biy at Peterfburgh, the company fuffering from the 

 clofenefs of the room, a gentleman broke a window 

 for relief; the confequence of which was, that the 

 cold air ruining in, caufed a vifible circum agitation of 

 a white fnowy fubitance *. 



Agreeably alfo to the fame principles it is evident, 

 that air is a fluid which has a fironger attraction for 

 the matter of fire than water, but that by means of 

 this infenfible evaporation the interfaces of the air, if 

 I may Ib exprefs myfelf, are filled with a quantity of 

 vapour, which being extremely rare, and being equally 

 difFufed, is invifible to us. If, however, a ftream of 

 cold air is introduced from any quarter, the caloric, 

 which is united with the water in the form of vapour, 

 will flow into the cold air to reftore the equilibrium, 

 and the vapour will be condenfed. The condenfa- 

 tion will fometimes be only fufficient 'to produce the 

 appearance of clouds, but at fome times it will be fuf- 

 ficient to caufe rain, which will fall in greater or lefler 

 quantities in proportion to the quantity of moifture in 

 the atmofphere, and the degree of cold in the con* 

 denfmg medium. 



* Edin. Phil. Tr. Vol. I. p. 48. 

 Like words congcal'd in northern air." 



HUDIBRAS. 



