actly the opposite of this. Lands which suffer most from drought are
most benefited by draining,--more in their greater ability to withstand
drought than in any other particular.

The reasons for this action of draining become obvious, when its effects
on the character of the soil are examined. There is always the same amount
of water in, and about, the surface of the earth. In winter there is more
in the soil than in summer, while in summer, that which has been dried out
of the soil exists in the atmosphere in the form of a _vapor_. It is held
in the vapory form by _heat_, which may be regarded as _braces_ to keep it
distended. When vapor comes in contact with substances sufficiently colder
than itself, it gives up its heat,--thus losing its braces,--contracts,
becomes liquid water, and is deposited as dew.

Many instances of this operation are familiar to all.

For instance, a cold pitcher in the summer robs the vapor in the air of
its heat, and causes it to be deposited on its own surface,--of course the
water comes from the atmosphere, not through the wall of the pitcher; if
we breathe on a knife blade, it condenses, in the same manner, the
moisture of the breath, and becomes covered with a film of-water;
stone-houses are damp in summer, because the inner surface of their walls,
being cooler than the atmosphere, causes its moisture to be deposited in
the manner described;(2) nearly every night, in summer, the cold earth
receives moisture from the atmosphere in the form of dew; a single large
head of cabbage, which at night is very cold, often condenses water to the
amount of a gill or more.

The same operation takes place in the soil. When the air is allowed to
circulate among its lower and cooler, (because more shaded,) particles,
they receive moisture by the same process of condensation. Therefore,
when, by the aid of under-drains, the lower soil becomes sufficiently
loose and open, to allow a circulation of air, the deposit of atmospheric
moisture will keep it supplied with water, at a point easily accessible to
the roots of plants.

If we wish to satisfy ourselves that this is practically correct, we have
only to prepare two boxes of finely pulverized soil,--one three or four
inches deep,--and the other fifteen or twenty inches deep, and place them
in the sun, at midday, in summer. The thinner soil will soon be completely
dried, while the deeper one, though it may have been previously dried in
an oven, will