[ 3=9 ] ^ 



TiTE influence of the' evaporation of each external fide of the 

 fheets extended at leafi to the diflancc of two feet, as the ther- 

 mometers indicate ; each fquare foot therefore on one external 

 fide lowered one degree the temperature of the two oppofite cubic 

 feet of air, and cbnfequently the evaporation from 35,25 fquare 

 feet lowered one degree the temperature of 72,5 cpbic feet of air ; 

 but thefe 35,25 feet exhaled -^09,78 grains of vapour. There- 

 fore the reception of 409,78 grains of .vapour in the temperature 

 of 62^ cooled one degree 72,5 cubic feet of air, or each cubic 

 foot of air was cooled on^ degree by the reception and folution 

 of 5,65 grains of vapour, and poflibly by a fmaller quantity, 

 for I cannot fay that the cold did not extend farther than the 

 diflance of two feet. 



Now of the hygrometer in the room the temperature being 

 62°, the complement vVas therefore ten grains, and as it flood at 

 LXXII. the ratio to its complement was 0,64; then as 10 X 0,64 

 = 6,4 grains, this muft have been the quantity of vapour which 

 Ae air originally contained in each of the two cubic feet; to 

 wliich,' if we add 5,65. w^ fhall have 12,05, which exceeds the 

 complement by 2,05 grains. It is probable then that thefe 2,05 

 grains were communicated to a greater diflance, and that 3,6 

 grains only remained in each cubic foot. The folution therefore 

 of 3,6 grains in a cubic foot of air in fixteen minutes, and in 



the 



