f the water supply of the arid and semi-arid West;
second, National Parks, of which there are seventeen, for the purpose of
preserving untouched places of natural grandeur and interest; third,
State Parks, for places of recreation and for conserving the water
supply; and fourth, military wood and timber reservations, to provide
Government fuel or other timber. Most military wood reserves were
originally established in connection with old forts.

The forest reservations, as they are by far the largest, are also much
the most important of these reserved areas.

Perhaps three-quarters of the population of the United States do not
know that over nearly one-half of the national territory within the
United States the rainfall is so slight or so unevenly distributed that
agriculture cannot be carried on except by means of irrigation. This
irrigation consists of taking water out of the streams and conducting it
by means of ditches which have a very gentle slope over the land which
it is proposed to irrigate. From the original ditch, smaller ditches are
taken out, running nearly parallel with each other, and from these
laterals other ditches, still smaller, and the seepage from all these
moistens a considerable area on which crops may be grown. This, very
roughly, is irrigation, a subject of incalculable interest to the
dwellers in the dry West.

It is obvious that irrigation cannot be practiced without water, and
that every ditch which takes water from a stream lessens the volume of
that stream below where the ditch is taken out. It is conceivable that
so many ditches might be taken out of the stream, and so much of the
water lost by evaporation and seepage into the soil irrigated, that a
stream which, uninterfered with, was bank full and even flowing
throughout the summer, might, under such changed condition, become
absolutely dry on the lower reaches of its course. And this, in fact, is
what has happened with some streams in the West. Where this is the case,
the farmers who live on the lower stretches of the stream, being without
water to put on their land, can raise no crops. Nothing, therefore, is
more important to the agriculturists of the West than to preserve full
and as nearly equal as possible at all seasons the water supply in their
streams.

This water is supplied by the annual rain or snow fall; but in the West
chiefly by snow. It falls deep on the high mountains, and, protected
there by the pine forests, accumu