62 Conjiderations on Dr. Huf ton's Theory of Rain. 



the idea of fomc other power operating jointly with the heat, 

 fuch as an altraftion between the bafe of air and water, I am 

 not cjuaHfied to determine ; but were it fo, this would in no- 

 wife affc6l the previous reafoning, as the conclufion reds en- 

 tirely on the temperature, i. e. in the do6tor's v'lew, the ca- 

 loric prefent, though they are in fa6l two diftincl; confidera- 

 tions which he has blended. 



In the concluding part of this effay, as it was originally 

 written, I had difcuifed the fubjeft of the folution of water 

 in air, and the fcveral modes of its precipitation, on chemical 

 principles; regarding moift air as a ternary compound of 

 bafe of air, water, and caloric, formed and fubfifting by 

 chemical attratlions, and decompofed by the operation of 

 the fame. 



Having fince perufed the excellent work of my friend Joha 

 Dalton *, which I have before alluded to, and having feen 

 and repeated fome of the principal experiments therein de- 

 tailed, I muft acknowledge that, although I might plead the 

 authority of a Kirwan f in fupport of the chemical theory of 

 evaporation, I am now difpofed to give up the idea of a proper 

 foluUon of water in air m toto. 



It ai)pears to me that nothing need be more clear, fimple, 

 and conckifive, than the experiments and deductions by which 

 the author attempts to prove that the evaporation of water 

 and feveral other liquids is a procefs unifornily regulated by 

 their temperature, the effeft of the latter in equal furfaces 

 being the fame tn vacuo and under the full preffiire of the at- 

 mofphere; the prefcnce of which has no other influence than 

 by its motion to multiply the furface of the liquid and carry 

 awav the vapour produced ; whence the diB'erence of quantity 

 evaporated in equal times in a moving and a ftagnant atmo- 

 fphere. The folvent power of .air on water may alfo, there- 

 fore, be fafelv clafled among ihofe caufes which arc not need- 

 ful to the efleft in queftion, and therefore not to be retained 

 in philofophical reafoning. 



* Experimental Effays on the Conftitution of mixed Gafcs; on the 

 Force of Steam or Vapour from Water and other Liquids in diflerent 

 Temperatures, both in a Torricellian Vacuum and in Air; on Evapora- 

 tion ; and on the Expanfion of Gafes by Heat. — Manchefter Memoirs, vol. v. 

 part 2. i£o'. 



\ Of the Variations of the Atmofiihcre, infcrted in the Irifli Traofac- 

 lions iSoi. 



XI, Qtnerul 



I 



