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the veffel, undoubtedly from the air in con tad with them. But 

 an inferiority in the temperature of water, amounting to lefs than 

 20°, will not prevent evaporation, but only proportionably dimi- 

 nifh it ; it is always brifkeft when the inferiority amounts only 

 to i^, or 2 degrees. 



Therefore, the nearer water approaches to the temperature of 

 the air, and yet remains one or two degrees below it, the more 

 evaporation is accelerated. This may help to explain fome expe- 

 riments of Achard, 1 5 Roz. Jour. p. 468. 



RicHMAN alfo obferved that when air is (bme degrees warmer 

 than water, evaporation is for a few minutes flower than it be- 

 comes afterwards; but after a few hours it is again retarded. The 

 reafon of which feems to be, that the inferiority of temperature 

 in the water is originally greateft, but gradually diminifhes, and 

 thus evaporation is accelerated ; but, at laft, the water attains an 

 equality of temperature, and then evaporation is retarded. 



This, however, can rarely happen, but when the mafs of water 

 is fmall, or its depth inconfiderable, or the air in a ftagnating 

 ftate. 



2°. When air is colder than the water expofed to it, the refult, 

 with refped to evaporation, is exadlly the reverfe of what happens 



when 



