( 49/) 
SECTION IV. 
Of the Analysis of Soils, and of the Agri- 
~eultural Nelations between Soils and 
Plants. 
We have seen that the earths have a threefold 
capacity ; that they receive and lodge the roots of 
plants and support their stems; that they absorb 
and hold air, water and mucilage—aliments neces- 
sary to vegetable life: and that they even yield a 
portion of themselves to these aliments. But we 
have also seen, that they are not equally adapted to 
these offices; that their parts, texture and quali- 
ties are different; that they are cold or warm, wet 
or dry, porous or compact, barren or productive, 
in. proportion as one or other may predominate in 
the soil: and that to fit them for discharging the 
various functions to which they are destined, each 
must contribute its share, and all be minutely di- 
vided and intimately mixed. In this great work 
nature has performed her part; but as is usual with 
her, she has wisely and benevolently left something 
for man to do. 
This necessary march of human industry, obvi- 
ously begins by ascertaining the nature of the sott. 
But. neither the touch, nor the eye, however prac- 
tised or acute, can in all cases determine this, 
Clay, when wet, is cold and tenacious—a descrip- 
tion that belongs also to magnesian earths: sand 
and gravel are hard and granular; but so also are 
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