can freely enter the soil; second, the land must be frequently
cultivated so that the water will be kept in the soil; third, the crops
must be properly rotated so as to use to best advantage the food and
water supply; fourth, humus must be freely supplied so as to keep the
soil in the best possible condition.

SECTION LXIX. IRRIGATION

Irrigation is the name given to the plan of supplying water in large
quantities to growing crops. Since the dawn of history this practice has
been more or less followed in Asia, in Africa, and in Europe. The
Spanish settlers in the southwestern part of America were probably the
first to introduce this custom into our country. In New Mexico there is
an irrigating trench that has been in constant use for three hundred
years.

[Illustration: FIG. 286. PUMPING WATER FOR IRRIGATION]

The most common source of water for irrigating purposes is a river or a
smaller stream. Artesian wells are used in some parts of the country.
Windmills are sometimes used when only a small supply of water is
needed. Engines, hydraulic rams, and water-wheels are also employed. The
water-wheel is one of the oldest and one of the most useful methods of
raising water from streams. There are thousands of these in use in the
dry regions of the West. Small buckets are fastened to a large wheel,
which is turned by the current of a stream. As the wheel turns, the
buckets are filled, raised, and then emptied into a trough called a
flume. The water flows through the flume into the irrigating ditches,
which distribute it as it is needed in the fields. In some parts of
California and other comparatively dry sections, wells are sunk in or
near the beds of underground streams, and then the water is pumped into
ditches which convey it to the fields to be irrigated.

Engines are often used for pumping water from streams and transferring
it to ditches or canals. The canals distribute the water over the land
or over the growing crops.

[Illustration: FIG. 287. THE MAIN DITCH OF AN IRRIGATION PLANT]

None of these methods, however, can be used for watering very large
areas of land. Hence, as the value of farm lands increased other methods
were sought. Shrewd men began to turn longing eyes on the wide stretches
of barren land in the West. They knew that these waste lands, seemingly
so unfertile, would become most fruitful as soon as water was turned on
them. Could water enough be found? New plans to pen up floods of water
we