gains two hundred grains when half filled with 
water and half with soil, the specific gravity of the 
soil will be 2 ; that is, it will be twice as heavy as 
water ; and if it gained one hundred and sixty- 
five grains, its specific gravity would be 18 25 , 
water being 1000. 
It is of importance, that the specific gravity of 
a soil should be known, as it affords an indication 
of the quantity of animal and vegetable matter it 
contains ; these substances being always most 
abundant in the lighter soils. 
The other physical properties of soils should like- 
wise be examined before the analysis is made, as 
they denote, to a certain extent, their composition, 
and serve as guides in directing the experiments. 
Thus, siliceous soils are generally rough to the 
touch, and scratch glass when rubbed upon it ; 
ferruginous soils are of a red or yellow colour ; 
and calcareous soils are soft. 
1. Soils, though as dry as they can be made by 
continued exposure to air, in all cases still contain 
a considerable quantity of water, which adheres 
with great obstinacy to the earths and animal and 
vegetable matter, and can only be driven off 
from them by a considerable degree of heat. The 
first process of analysis is, to free the given weight 
of soil from as much of this water as possible, with- 
out in other respects affecting its composition ; and 
this may be done by heating it for ten or twelve 
minutes over an Argand’s lamp, in a basin of porce- 
lain, to a temperature equal to 300 Fahrenheit; 
and if a thermometer is not used, the proper degree 
may be easily ascertained, by keeping a piece of 
l 2 
