"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 its heat. The experiments of Count Rumford, showing that heat is not propagated downward in fluids, may be found at page 273. This is a principle too important to be overlooked, especially in New England, where we need every aid from Nature and Art, to contend successfully against the brevity of the planting season. Soil saturated with cold water, cannot be warmed by any amount of heat applied to the surface. Warm water is lighter than cold water, and stays at the surface. In boiling water in a kettle, we apply fire at the bottom, and no amount of heat at the surface of the vessel would produce the desired effect. So rapid is the passage of heat upward in water, that the hand may without injury be held upon the bottom of a kettle of boiling water one minute after it has been removed from the fire. The following experiments and illustrations, from the _Horticulturist_ of Nov. 1856, beautifully illustrate this point: "RATIONALE OF DRAINING LAND EXPLAINED.