[ 320 ]' 



^aperture, would rife to the height of upwards of 15,76 altitu- 

 dinal inches, which is nearly the quantity of rain that falls in 

 London in the drieft years. 



Doctor Hales, from fome experiments, concludes the eva- 

 poration from a furface of earth to be nearly the fame in 

 winter as in fummer, as it contains more moifture in the former 

 feafon, and ftates its proportion to that from water as three to 

 ten, but by earth he means earth divefted of vegetables, which 

 fcarce ever occurs, i Hales, p. 55; and with his experiments thofe 

 of the Reverend Mr. Williams, of Bradford, in New England, 

 nearly agree, 2 Amer. Tranf. 120. But the evaporation from a 

 fquare foot of earth covered with vegetables, and duly fupplied 

 W'ith moifture, is much greater than that from mere water, as 

 follows from his experiments, and ftill more demonftrably from 

 the great and fpeedy evaporation from the multiplied furfaces 

 in houfes of graduation. In a cultivated country, like the vici- 

 nity of London, it is to that from water at leaft as fifteen to ten. 

 Bazin, from two years obfervations on moift earth, infers that 

 it evaporates much more quickly than an equal volume of water. 

 Hift. Par. Acad. 1741. 



Rain does not prevent evaporation, as I have~ frequently ob- 

 ferved. 



Saussure's 



