140 TECHNOLOGY. 
extremes, to a depth of nine to twelve inches, is most favorable to the 
growth of cultivated plants. In general the greater the preponderance of 
sand the lighter and more easily moved is the soil, while a preponderance 
of clay gives it exactly opposite qualities. . 
The food of plants consists of water and the remains of decayed vegetable 
bodies, which in the state in which it is found in the soil is called humus. 
Soils may be divided into, 1. very stiff clay; 2. moderately stiff clay ; 
3. sandy clay; 4. morst, jme-grained, sandy soil; 5. dry, coarse-grained 
sand. 
1. StrrF Cay is in best condition when, either by nature or liberal treat- 
ment with manure, it contains a rich supply of humus, or when the decom- 
position of the humus has been effected by cultivation which has brought 
every portion of the soil in contact with the atmosphere, and which at the - 
same time has eradicated the weeds. As such soils, however, on account 
of their impermeability, are liable to suffer from an excess of moisture, care 
is necessary that good water-furrows be provided to carry off superfluous 
water, which otherwise might stand in pools upon the surface. Attention 
to this is important to the prosperity of every plant, but indispensably 
necessary to the growth of the cereals. 
2. Mopreratety Stir Cray or Cray Loam. In general, what has been 
said of stiff clay holds good of this soil also; it is, however, easier to work, 
suffers less from moisture, and thus is better adapted to the growth of grain. 
On the other hand, it is more easily deprived of its humus by a succession 
of crops; but by the admixture of lime the assimilation of its elements is 
promoted, and even when there is a lack of humus, with favorable weather, 
good crops may be expected. 
_ Each of these grades of soil is, however, easily baked or hardened upon 
the surface by the sun; on this account a covering of vegetation is of great 
importance to the development of the strength of the soil. 
38. Sanpy Cray or Sanpy Loam. This soil permits the ready entrance 
of the air, and in consequence its cultivation presents comparatively few 
difficulties ; its natural products, weeds, require a corresponding greater 
degree of care. This soil may be said to be in the best order when the manure 
applied to small grains is decomposed and mixed with the earth. Care is 
requisite to retain the surface water instead of leading it off, and to compact 
the soil during its cultivation by the use of the roller. Furthermore the 
ready access given to the atmosphere causes a constant decomposition of its 
humus and manure until interrupted by frost, and consequently such soils 
should never be left without some growing crop. On this account such 
Jand should not be fallowed, as the air thus carries off its useful gases and 
the soil soon becomes sterile. 
4. Most, Frve-Grarvep, Sanpy Som. The peculiarity of this soil con- 
sists in the extreme fineness of its sand, which exists in a state of dust so 
minutely divided as to resist the entrance of the air to an equal degree with 
those soils containing too much clay. Water is thus prevented from escap- 
ing, and weeds grow with great luxuriance. The sun hardens this soil so 
as to render ploughing extremely difficult, and the atmosphere is completely 
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