424 Mr. de Luc on Evaporation. 
meter, it is evident, that they are independent of the modifi- 
cations of air ; and that it may safely be concluded : “ That 
“ the product of evaporation is always of the same nature, 
“ namely, an expansible fluid, which, either alone or mixed 
“ with air, affects the manometer by pressure and the hy- 
“ grometer by moisture, without any difference arising from 
“ the presence or absence of air ; at least without any per- 
•* ceived hitherto/' 
