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Here two furfaces were expofed to evaporation, each confi fl- 

 ing of one hundred and thirty fquare inches. The time of ex- 

 pofition was one-third of that of my experiments, but the furfaces 

 were ten times greater. The mean temperature of the three ex- 

 periments on the plain was 49°, 5, the mean hygrometrical height 

 LXXXII. and the mean quantity evaporated fixteen grains. This 

 refult differs confiderably from the mean of mine made at nearly 

 the fame temperature, but different degrees of moifture in the 

 air, and under a furface ten times fmaller, and in a portion of 

 time three times greater. If his furfaces and times were reduced 

 to mine, then the evaporation would be but 4,8 grains; for fmce 

 two hundred and fixty fquare inches give fixteen grains, twenty- 

 fix fhould give 1,6 grains ; and this quantity multiplied into 

 3 = 4,8 grains ; the difference may proceed from the low fatu- 

 rability of the air in his experiments, whofe efflsd, as already 

 faid, is three times greater than that of temperature, and polilbly 

 from the attradlion o£ the linen. I have found no obfervations 

 among mine exadly comparable in their circumflances with 

 his. 



The cold produced by evaporation is an effed deferving much 

 attention in a meteorological point of view. In the months of 

 July, Auguft and September, 1783, I made numerous experi- 

 ments with a view of detedling the connexion of this efFed with 



the 



