ELEMENTS OF AGRICULTURE. 
BS 
the adhesiveness of their parts (due to the plastic property 
of the alumine they contain); and this property alone will 
enable even the inexperienced to discriminate them. A 
stiff clay when dried, by either natural or artificial heat, 
oecomes so hard as to resist a considerable mechanical 
pressure. This property makes it valuable for the manu¬ 
facture of bricks, tiles, pottery, etc. 
27. On account of the tenacity of such soils, they are 
tilled with more difficulty than the freer soils. They re¬ 
quire to fertilize them a larger proportion of manures ; but 
they retain the effects of these manures a longer time. 
They are better suited to the cultivation of plants with 
fibrous than with fleshy roots, or tubers. 
28. Soils of this class, as of every other, possess many 
degrees of natural fertility. Tne poor clays form, for the 
most part, an unprofitable soil; because, while their powers 
of production are inconsiderable, the expenses of tilling 
them are large. The clay soils of this character are gene¬ 
rally of little depth, and rest upon a retentive subsoil. 
The natural herbage they produce is coarse, and not very 
nutritious; and they are not well suited to the cultivated 
grasses, and other herbage plants. They are little fitted 
for the growth of turnips, or other plants with fleshy roots 
or tubers. Such soils have everywhere local names, which 
sufficiently denote their qualities ; and they are termed, by 
not an improper figure, cold soils. 
29. Very different in their value and nature are the 
richer clays. These bear weighty crops of aJl tire culti¬ 
vated kinds of small grain ; they do not excel the better 
soils of other classes so greatly in the production of corn 
and still less in that of barley, in which the lighter loams 
may surpass them. But they are unequalled in the pro¬ 
duction of wheat, and in many places derive their de¬ 
scriptive appellation from that circumstance, being termed 
i cheat soils. They will yield large returns of the culti 
