149 
they will effervesce with acids ; if siliceous, they 
will be sufficiently hard to scratch glass ; and if of 
the common aluminous class of stones, they will 
be soft, easily cut with a knife, and incapable of 
effervescing with acids. 
S, The greater number of soils, besides gravel 
and stones, contain larger or smaller proportions 
of sand of different degrees of fineness ; and it is 
a necessary operation, the next in the process of 
analysis, to detach them from the parts in a state of 
more minute division, such as clay, loam, marie, 
vegetable and animal matter, and the matter solu- 
ble in water. This may be effected in a way suf- 
ficiently accurate, by boiling the soil in three or 
four times its weight of water ; and when the tex- 
ture of the soil is broken down, and the water 
cool, by agitating the parts together, and then 
suffering them to rest. In this case, the coarse 
sand will generally separate in a minute, and the 
finer in two or three minutes, whilst the highly- 
divided earthy, animal, or vegetable matter, will 
remain in a state of mechanical suspension for a 
much longer time ; so that by pouring the water 
from the bottom of the vessel, after one, two, or 
three minutes, the sand will be principally separ- 
ated from the other substances, which, with the 
water containing them, must be poured into a 
filtre, and after the water has passed through, col- 
lected, dried, and weighed. The sand must like- 
wise be weighed, and the respective quantities 
noted down. The water of lixiviation must be pre- 
served, as it will be found to contain the saline and 
l 3 
