HOT WINDS. 4 
oO 
that the knowledge we are gaining of the unknown past, as well 
as the records of more recent years, point to the recurrence of 
great fluctuations in the annual rainfall of this section, and it 
seems probable that such changes follow series of years, and that 
the recedence of our lakes may be followed by periods of higher 
water. 
But the influence of the cultivation of the soil on water sup- 
plies must be taken into account in this connection, for it is 
undoubtedly true that man has changed the conditions of the 
soil sufficiently to greatly influence the run-off. The breaking 
up of large areas of prairie sod, with its low rate of evaporation, 
and the planting of such land to agricultural crops with a rela- 
tively high rate of evaporation, has resulted in a loss of soil 
water. Then the cultivated soil takes up more water than the 
sod-bound prairie slopes, so that it does not have so good an 
opportunity to collect in lakes and swamps, which often supplied 
the water of wells. And further, the straightening and cleaning 
out of water courses, and the draining of swamps in the effort 
to get arable land, has had a similar effect on subsoil water sup- 
plies. 
HOT WINDS. 
The hot winds of the plains which so often cause serious 
injury to farm crops in Kansas, Nebraska and the Dakotas have 
been ascribed to the arid “staked” plains, whence, taking a north- 
easterly direction, they draw all the moisture from the vegeta- 
tion with which they come in contact. The view has also been 
presented that they have their origin on the Pacific Coast, 
ascend the Rocky Mountains, lose their moisture and descend 
on the eastern slopes. But all theories that ascribe their origin 
to a distant source are inadequate to explain their phenomena. 
For instance, all who are acquainted with these winds know 
that they blow only during very dry weather, when the earth is 
heated very hot, that a good rain speedily brings them to an 
end, and that they blow only during the daytime, commencing 
about 9 A. M. and continuing until sundown. This daily move- 
ment is often constant for several weeks, showing that there is 
evidently some connection between them and the course of the 
sun. For these reasons and others which would require too 
