suan.

In the western highland region of the United States considerable areas
already have been made productive by irrigation, and it is estimated
that about two million acres of barren land can be reclaimed by
impounding the waters of the various streams now running to waste.

The distribution of rain with respect to the season in which it falls is
quite as important as its distribution with respect to quantity. In
tropical regions the ocean winds, and therefore the rainfall, come from
the east. The eastern slopes of such regions, therefore, have a season
in which rains may be expected daily, and another in which no rain falls
for several months. In the temperate zones seasonal rains for a similar
reason are on the western coasts.

Thus on the Pacific coast of the United States the rainfall varies from
about one hundred inches in southern Alaska to about twelve in San
Diego, Cal. Practically all the rain falls between October and the
following May; very little or none falls in the interval between May and
October. As a result, ordinary turf-grass, which will not withstand long
droughts, grows in only a few localities of the Pacific slope. It is
replaced by hardier grasses whose roots, instead of forming turf, grow
very deep in the soil.

Common clover will not grow in this region unless irrigated; it is
replaced by burr-clover, a variety of the plant that will not thrive in
moist regions. Now the quality of the merino wool clip of California
depends in no slight degree upon the burr-clover and other food-products
that thrive in regions of seasonal rains; that is, a great commercial
industry exists because of this feature of rainfall, and it could not
long survive in spite of it.

[Illustration: CLIMATICALLY ADAPTED TO CULTIVATION--THE LOWLANDS
PRODUCE BREAD-STUFFS AND FRUIT; THE MOUNTAIN-SLOPES ARE GRAZING REGIONS]

The seasonal rainfall also affects other agricultural industries. The
sacked wheat-crop may be left in the field without cover or protection
until the time is convenient for shipping it. The absence of summer
rains makes possible in California what would be out of question in the
Mississippi Valley, where a rainstorm may be expected every few days.

The quality of certain fruits depends largely on the season during which
the rainfall occurs. Apples, pears, and grapes grown in regions having
dry summers have usually a very superior flavor. The raisin-making
industry of California also depends on the s