116 
Annual Report of the 
cation of food by animals. It is preparing the food for the diges¬ 
tive organs of the plant. 
The difference between a fertile and a sterile soil is often attribu¬ 
table to this one cause, a want of sufficient porosity to allow the 
air and moisture to enter it and decompose the mineral matter, 
changing such as is needed to that form capable of being taken up 
by the roots of plants. 
This is the great difference between soils and subsoils, and the 
latter may be made fertile by the same pulverization and exposure 
to which the former has been subjected. It is principally by the 
gradual chemical changes in the composition of the soil brought 
about by the decomposing action of heat, moisture and air, that 
soils are continued in a state of fertility from year to year. These 
natural forces are continually at work for the farmer, and their 
work will be well and thoroughly done, in proportion to the oppor¬ 
tunity he gives them, by furnishing a light, porous and well pulver¬ 
ized soil. 
Were there, then, no other reason for thorough culture than this 
one, it must be greatly to the interest of the farmer to cultivate 
well and thoroughly, to plow deep and keep his soil well stirred, in 
order that his crops may yield the largest possible harvest. But 
there are still other reasons why the soil’s fertility is increased by 
its being finely pulverized. Those properties of soils that are usu¬ 
ally termed “plij’-sical,” those in which the action is mechanical rath¬ 
er than chemical, are also in a high degree dependent upon the fine¬ 
ness of their particles. The first of these to which I wish to call at¬ 
tention is the power possessed by soils of absorbing certain substan¬ 
ces, and of condensing upon the surface of the particles of which 
they are composed moisture and gases existing in the atmosphere. 
If a dry sponge be dipped in water and then squeezed until no 
more water can be obtained from it, it is not dry as before, but still 
contains a large amount of water, which exists, not as water, but 
as moisture held upon the surface of the particles composing the 
sponge. The amount of water so held, is in direct proportion to 
the extent of surface with which the water comes in contact, for 
the cause of the waters being held there is that surfaces have a 
strong attraction for moisture. Any one who has had occasion to 
thoroughly dry a glass tube or bottle, knows something of the per¬ 
sistence with which moisture adheres to the surface of glass. Soft 
