[ 3o8 ] 



and caufed part of it to feparate from its interior'; at leaft I fee no 

 other caufe. 



Although the Englifh cubic foot be fmaller than the French, 

 and the French grain fmaller than the Engliih, yet I have left the 

 quantities given by Sauffure unaltered, becaufe I am perfuaded 

 that even the Engliih cubic foot of air, at leaft in temperatures ex- 

 ceeding 60'^. contains at every hygrometrjcal degree much more 

 moifture than is indicated by thefe tables. This our author 

 acknowledges, § 47, and well explains why the whole of the 

 moifture contained in a cubic foot of air can never be extra£ted ; 

 befides it feems to me, that under the veffels in which his experi- 

 ments were made, the air not having fufficient power to expand 

 itfelf as it fliould, on receiving moifture, could not take up the 

 whole quantity which, were it at liberty, it would take up in 

 hiah temperatures, that is above 75^, and therefore appeared fa- 

 turated, when it, if at liberty, would not be fo. 



As both faturability in a given heat, and alfo an in.creafe of 

 heat, promote evaporation, it may be ail<ed, which of them exerts 

 the greateft influence ? This curious queftion Sauflure has beau- 

 tifully refolvcd from obfervations on evaporation on the Col de 

 Geant, compared with thofe made at Geneva^ and by an ingenious 

 calculation of the rcfulting efie£l of each of them. Voy. aux. 

 Alpes, § 2060. 



The 



