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and ill another cafe colder than water, by an equal number of de- 

 grees, it ftiould feem, that in equal times the evaporation would 

 be greater in the hotter air than in the colder, becaufe colder air 

 is fooner faturated, requiring only to produce faturation a fmaller 

 proportion of moifture ; yet as, on the other hand, hot air depofits 

 mojfture on water fome degrees colder, this point is not yet ab- 

 Iblutely fettled. 



Section II. 



Of the Influence of Affinity. 



The next property of air materially concerned in promoting 

 evaporation is its affinity to water. That this affinity is very ftrong, 

 appears by the difficulty of depriving water of the air it contains, 

 either by ebullition, or by the a(ftion of the air-pump, as Mr. De 

 Luc has long fmce fhewn. This affinity, neverthelefs, does not 

 fcem to me a chemical affinity, for water and air do not form a 

 tertitim quid, as bodies chemically united do ; and they are in great 

 meafure feparable by mere mechanical means, as by the adion of 

 the air-pump, which bodies chemically united never are, and 

 hence, SaufTure very properly calls it, an hygrometrical affinity : 

 yet it refembles chemical affinity thus far, that it ads by attradion, 

 and promotes an union, at leaf! of adhefion, and this attradion 

 has its limit, which is alfo called faturation. 



Of 



