AGRICULTURE. 141 
excluded. This so-called cold soil must be so managed in cultivation as to 
destroy knot-grass, charlock, and other weeds which are apt to infest it, 
and to forward the decomposition of its humus. This is accomplished not 
so much by fallow as by cultivation in hills upon long manure. Potatoes 
and garden vegetables, when used for food, are not so well adapted to the 
purpose, as the coldness of the soil retards them, and they flourish only in 
very warm days. Naked fallows evaporate the gases which should nourish 
vegetation. As this soil also suffers from too much moisture, the lands 
should be laid off narrow and the furrows be well cleaned out, particularly 
for winter grain. 
5. Dry, Coarse-Grarvep, Sanpy Som. This is the direct opposite in all 
respects of clay soil, and must be managed in an entirely different manner. 
If in the latter the entrance of the atmosphere is resisted, in the case before 
us it is too much encouraged, and the ceaseless evaporation may impoverish 
the soil before it has borne a single crop. This soil is only fit for grain 
when it can be shaded by a heavy cover of foliage, which impedes the 
evaporation of the gases. Its weeds are eradicated by leaving it for many 
years in meadow, when they are prevented from perfecting their seed, and 
thus ultimately are extinguished; even knot-grass, the worst and most 
troublesome of all weeds, cannot endure many years after the ground is 
laid down to meadow. As with the soils in which clay predominates care 
is not necessary to conduct off superfluous water, in this case every means 
must be resorted to, to retain the moisture for the use of vegetation. 
Neither land nor water furrows are necessary, and the roller must be used 
with every crop, to compact and consolidate the soil as much as possible. 
This classification of soils is important only so far as the decomposition 
of humus and the growth of weeds are concerned; thus far it is sufficient. 
A classification as regards fertility requires that other attendant circum- 
stances be noticed, as the subsoil, the character of the surface (whether flat, 
rolling, or otherwise), and the presence of other chemical and mineral sub- 
stances. The knowledge of soils thus classified is taught by Agronomy, 
which treats of the different elements of soils and the relation they bear to 
each other. 
There are also exterior signs to be noticed in judging of soils. Their 
tenacity, as manifested in ploughing and harrowing ; its excess in one case, 
while it is entirely wanting in another ; their different powers of absorption 
and retention of moisture; their color when wet, and their peculiar odor 
indicating the presence or the absence of humus. 
We will now turn our attention to some of the most common agricultural 
tools. 
B. Agricultural Tools. 
1. Tae Proven. Ploughing serves to open the soil for the admission of 
air and moisture to the organic matter which it contains, and which is thus 
decomposed and fitted to serve as food for vegetation. The operation is 
more or less necessary, more or less difficult, according as the soil is stiff 
and tenacious, or loose and porous. Another object to be accomplished by 
ICONOGRAPHIC ENCYCLOPADIA.—VOL, IY. 46 721 

