[ 3i^ 1 



where the barometer flood at 20 inches, and on a plain 

 where it flood at 28,77. It would be tedious to defcribe the par- 

 ticulars, but the general refult was, that' when the velocity of 

 the wind was about twenty-eight miles per hour, or forty feet 

 fer fecond, the cold produced by evaporation from a moift 

 fpunge of about three fquare inches, in which a thermometer was 

 inferted, was as follows* : 



On the Mountain. 



Though various experiments have been inflituted to afcertain 

 the cold produced by evaporation in evaporating liquids, yet I 

 know of none wherein the cold produced in air, by the evapo- 

 ration of liquids in contad with it, has been examined ; hence 



with 

 • Voy. aux Alpes, § 2o5o. 



