oil in the lamp-chimney
is clay and well packed, the water will quickly rise to the top.

By filling three or four lamp-chimneys with as many different
soils, the pupil will see that the water rises more slowly in some
than in others.

Now take the water pan away, and the water in the lamp-chimneys
will gradually evaporate. Study for a few days the effect of
evaporation on the several soils.

SECTION V. DRAINING THE SOIL

A wise man was once asked, "What is the most valuable improvement ever
made in agriculture?" He answered, "Drainage." Often soils unfit for
crop-production because they contain too much water are by drainage
rendered the most valuable of farming lands.

Drainage benefits land in the following ways:

1. It deepens the subsoil by removing unnecessary water from the spaces
between the soil particles. This admits air. Then the oxygen which is in
the air, by aiding decay, prepares plant food for vegetation.

2. It makes the surface soil, or topsoil, deeper. It stands to reason
that the deeper the soil the more plant food becomes available for plant
use.

3. It improves the texture of the soil. Wet soil is sticky. Drainage
makes this sticky soil crumble and fall apart.

4. It prevents washing.

5. It increases the porosity of soils and permits roots to go deeper
into the soil for food and moisture.

6. It increases the warmth of the soil.

7. It permits earlier working in spring and after rains.

[Illustration: FIG. 9. LAYING A TILE DRAIN]

8. It favors the growth of germs which change the unavailable nitrogen
of the soil into nitrates; that is, into the form of nitrogen most
useful to plants.

9. It enables plants to resist drought better because the roots go into
the ground deeper early in the season.

A soil that is hard and wet will not grow good crops. The
nitrogen-gathering crops will store the greatest quantity of nitrogen in
the soil when the soil is open to the free circulation of the air.
These valuable crops cannot do this when the soil is wet and cold.

Sandy soils with sandy subsoils do not often need drainage; such soils
are naturally drained. With clay soils it is different. It is very
important to remove the stagnant water in them and to let the air in.

When land has been properly drained the other steps in improvement are
easily taken. After soil has been dried and mellowed by proper drainage,
then commercial fertilizers, barnyard