2 OF CLOUDS. CHAP. 1. 



Before I speak of the origin, suspension, 

 and varieties of clouds, and of their destruc- 

 tion by rain, some preliminary observations 

 will be necessary. Aqueous particles, and 

 other volatile substances, may be either dif- 

 fused in the air, or may be dissolved in it. 

 But diffusion and solution are things quite 

 different from chemical combination. 



A cloud may either be so diffused as to cease 

 to be visible as an aggregate, or it may be 

 taken into solution by the air : in the former 

 case, a hazy turbidness ; in the latter, an 

 additional clearness of the sky ; would probably 

 be the consequence.* 



the qualities of the thing they represent; they serve merely 

 as hints for the production of ideas. See TOOKE'S EirJa 

 nrefoevra, 4to. vol. ii. 196. 



* A cloud may be the consequence of vapour, upraised into 

 the air, and afterward more condensed into visible particles, 

 by an alteration either in the temperature or pressure, where- 

 by the air cannot hold so much vapour in solution as before. 

 Some recent discoveries have, however, led to a supposition 

 that, under particular circumstances, the air itself may be 

 decomposed so as to deposit water, which may again be 

 taken up by the air. Thus we come back again to the old 

 opinion of Aristotle: Ei 15 yiverai v$iu s% ae^if, xai aijfl e% 

 vSa.ro;, &a riva. cror' amav ou <rvvHrra,Tou v<pij xara rox avw 

 nifw, &c. Meteor, lib. i. cap. 3. 



