61

In the troy pound, supposing the quantity ofwater to amount to 100 grains, the quantities

of the three earths will be,

Coarse Silex - - 2122

Finer ... 792

-2914

Argill - 622

Calx - 2122

5658

Hence we see that in the drier countries,where the fall of rain is but 20 inches, the soil,to be fertile, must be closer, and the quantityof calcareous earth much increased, and thatof the silicious much diminished. Thus, inthe climate of Turin , where the fall of rain ex-ceeds 40 inches, the proportion of siliciousearth is from 77 to 80 per cwt. and that of cal-careous, from 9 to 14, to suffer this excess ofrain more easily to evaporate. In the climateof Upsal, where the fall of rain is 24 inches,the proportion of silex is only 56 per cwt. but