184 HOW CROPS FEED, 
ration are vastly more numerous and less wide than in 
purer clays. Such a soil does not “cake,” but remains 
friable and powdery. 
Marly soils (containing carbonate of lime) are especially 
prone to fall toa fine powder during drying, since the 
carbonate of lime, which, like sand, shrinks very little, is 
itself in a state of extreme division, and therefore more 
effectually separates the clayey particles. The unequal 
shrinking of these two intimately mixed ingredients ac- 
complishes a perfect pulverization of such soils. On the 
cold, heavy soils of Upper Lusatia, in Germany, the appli- 
cation of lime has been attended with excellent results, 
and the larger share of the benefit is to be accounted for 
by the improvement in the texture of those soils which 
follows liming. The carbonate of lime is considerably 
soluble in water charged with carbonic acid, as is the wa- 
ter of a soil containing vegetable matter, and this agency 
of distribution, in connection with the mechanical opera- 
tions of tillage, must in a short time effect an intimate 
mixture of the lime with the whole soil. A tenacious clay 
is thus by a heavy liming made to approach the condition 
of a friable marl. 
Heaving by Frost.—Soils which imbibe much water, 
especially clay and peat soils, have likewise the disagree- 
able property of being heaved by frost. The expansion, 
by freezing, of the liquid water they contain, separates the 
particles of soil from each other, raises, in fact, the surface 
for a considerable height, and thus ruptures the roots of 
grass and especially of fall-sowed grain. The lifting of 
fence posts is due to the same cause, 
§ 8, 
ADHESIVENESS OF THE SOIL. 
In the language of the farm a soil is said to be heavy 
or light, not as it weighs more or less, but as it is easy or 
