146 
In cases when the general nature of the soil of a 
field is to be ascertained, specimens of it should be 
taken from different places, two or three inches 
below the surface, and examined as to the similarity 
of their properties. It sometimes happens, that 
upon plains the whole of the upper stratum of the 
land is of the same kind, and in this case one 
analysis will be sufficient ; but in vallies, and near 
the beds of rivers, there are very great differences, 
and it now and then occurs that one part of a field 
is calcareous, and another part siliceous ; and in 
this case, and in analogous cases, the portions dif- 
ferent from each other should be separately sub- 
mitted to experiment. 
Soils, when collected, if they cannot be imme- 
diately examined, should be preserved in phials 
quite filled with them, and closed with ground-glass 
stoppers. 
The quantity of soil most convenient for a per- 
fect analysis, is from two to four hundred grains. 
It should be collected in dry weather, and ex- 
posed to the atmosphere till it becomes dry to the 
touch. 
The specific gravity of a soil, or the relation of 
its weight to that of water, may be ascertained by 
introducing into a phial, which will contain a 
known quantity of water, equal volumes of water 
and of soil ; and this may be easily done by pour- 
ing in water till it is half full, and then adding 
the soil till the fluid rises to the mouth ; the dif- 
ference between the weight of the soil and that 
of the water will give the result* Thus, if the 
bottle contains four hundred grains of water, and 
