A committee of the New York Farmers' Club, which visited the farm of
Prof. Mapes, in New Jersey, in the time of a severe drought, in 1855,
reported that the Professor's fences were the boundaries of the drought,
all the lands outside being affected by it, while his remained free from
injury. This was attributed, both by the committee and by Prof. Mapes
himself, to thorough-drainage and deep tillage with the subsoil plow.

Mr. Shedd, in the _N. E. Farmer_, says:

"A simple illustration will show the effect which stagnant water,
within a foot or two of the surface, has on the roots of plants.

"Perhaps it will aid the reader, who doubts the benefit of
thorough-draining in case of drought, to see why it is beneficial.

[Illustration: Fig. 95. Section of land before it is drained.]

[Illustration: Fig. 96. Section of land after it is drained.]

"In the first figure, 1 represents the surface soil, through which
evaporation takes place, using up the heat which might otherwise go
to the roots of plants; 2, represents the water table, or surface
of stagnant water below which roots seldom go; 3, water of
evaporation; 4, water of capillary attraction; 5, water of
drainage, or stagnant water.

"In the second figure, 1 represents the surface-soil warmed by the
sun and Summer rains; 2, the water-table nearly four feet below the
surface--roots of the wheat plant have been traced to a depth of
more than four feet in a free mold; 3, water of capillary
attraction; 4, water of drainage, or stagnant water."

CHAPTER XV.

TEMPERATURE AS AFFECTED BY DRAINAGE.

Drainage Warms the Soil in Spring.--Heat cannot go down in Wet
Land.--Drainage causes greater Deposit of Dew in Summer.--Dew warms
Plants in Night, Cools them in the Morning Sun.--Drainage varies
Temperature by Lessening Evaporation.--What is Evaporation.--How it
produces Cold.--Drained Land Freezes Deepest, but Thaws Soonest,
and the Reasons.

_Drainage raises the temperature of the soil, by allowing the rain to
pass downwards._ In the growing season, especially in the Spring, the
rain is considerably warmer than the soil. If the soil be saturated with
the cold snow-water, the water which falls must, of course, run away
upon the surface. If the soil be drained, the rain-water finds ready
admission into it, carrying and imparting to it a portion of