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And, i<>. with refped to temperature, the air in contad with 

 water may be either of the fame temperature' as the water, or it 

 may be -warmer, or colder. 



If both the water and the air be of the fame temperature, it 

 appears by the experiments of Richman, that evaporation pro- 

 ceeds moft flowly, as in that cafe the air in con tad with the water 

 foon becomes faturate ; and though moifl air is fpecifically h'ghter 

 than dry air, yet that happens only when both are of the fame 

 temperature, or the dry air colder. Now air in taking up moifture 

 is cooled by it, and therefore continues its contad with water, 

 and thus the progrefs of evaporation is checked. 



.. Again, if the air be •warmer than the water, and its tempera- 

 ture between 60° and 70°, and if the water be 14.'' colder, or 

 more, in that cafe thei'e is no evaporation at all, but, on the con- 

 trary, the air depofits the vapours it had previoufly pofTcfled ; for 

 Richman found the fcale in which the water was at firft fully 

 counterbalanced, gradually to fink, and drops of water appeared 

 on the fides of the vefiMsl. But if the water be only ri° colder, 

 it will evaporate indeed, but flowly. But if the air be at any 

 temperature between 75*^ and 87°, then evaporation is prevented 

 'only when and while the water is 20 degrees colder, or more ; 

 and water in Richman's experiments was depofited on the fides of 



O 2 the 



