118 
Annual Be port of the 
able to raise water by this power for the relief of the thirsty crops. 
Again then, for the purpose of protection from drought, deep and 
thorough tillage is necessary on the part of every farmer, and 
other conditions remaining the same, the production will be largely 
in the ratio of the depth and thoroughness of the cultivation. 
All soils possess, to a greater or less degree, the power of absorb¬ 
ing from water, that is slowly filtered through them, solid matter 
held in solution by the water. The power of soils in this respect is 
doubtless familiar to all. 
Thus every farmer knows that if the washings of his barn-yard 
can be filtered through the soil of adjacent fields, the larger pro¬ 
portion of the fertilizing ingredients in solution in the water will 
be left in the soil, while the water will pass away comparatively 
pure. Deeply colored syrups were formerly decolorized b}^ passing 
them through layers of clay. 
• The common house filter depends upon the same principle, the 
impurities of the water being taken out by a layer of animal char¬ 
coal. 
This absorbent power of soils depends upon the attraction exist¬ 
ing between the surface of the particles of which the soils are com¬ 
posed, and the surface of the particles of solids held in solution. It 
is again the result of the attraction between surfaces, and conse¬ 
quently the greater the amount of surface, the more complete will 
be the abstraction of any solid matter held in solution. 
Now rain brings from the atmosphere appreciable quantities of 
valuable fertilizing materials, especially nitric acid and ammonia, 
and these are absorbed by the soil as the water slowly percolates 
through it, if its attractive power is sufficient, and that, upon the 
same soil, is in proportion to the fineness of the particles. For that 
s the index of the amount of surface by which the dissolved parti¬ 
cles will be attracted and held. Here again then, we have arrived 
at the same conclusion as before. Soils need to be thoroughly pul¬ 
verized that they may take from water, with which they come in 
contact, the valuable fertilizing material held in solution by it. 
Manures are applied to soils for several reasons. First, that they 
may furnish to the growing plants certain constituents that con¬ 
tribute directly to their growth. This office of manure is quite of¬ 
ten supposed to be the principal function in aid of the growth of 
crops. Manure does indeed often furnish material that is of direct 
