. Soils, their properties and management . l means a lower-ing in conductivity. Humus, therefore, must be listedas » second factor tending to vary the movement of heatthrough soils. A third factor is the structural conditionof the soil under examination. Wagner ^ has shown inthis regard that the more compact a soil, the faster isthe conduction of heat. This is probably due to the moreintimate contact of the soil grains, and a consequentcutting-down of the insulation factors and diminutionof the transfer resistance. 223. Influence of moisture on heat conductivity in soil.—The greatest single fa
. Soils, their properties and management . l means a lower-ing in conductivity. Humus, therefore, must be listedas » second factor tending to vary the movement of heatthrough soils. A third factor is the structural conditionof the soil under examination. Wagner ^ has shown inthis regard that the more compact a soil, the faster isthe conduction of heat. This is probably due to the moreintimate contact of the soil grains, and a consequentcutting-down of the insulation factors and diminutionof the transfer resistance. 223. Influence of moisture on heat conductivity in soil.—The greatest single factor to be considered in conduc- ^ Wagner, F. Untersuchungen iiber das Relative Warrae-leitungsvermogen Verschiedner Bodenarten. Forsch. a. d. , Band VI, Seite 1-51, 1885. SOIL HEAT 311 tivity study, however, is the moisture content of the following curve for quartz powder, taken from Pat-tens ^ work, illustrates its effect and shows how its influ-ence may heavily override the factors already mentioned. .C03. Ml S /O /S Fig. 49.—Effect of moisture upon the apparent specific volume, heatconductivity, and diffusivity of coarse quartz powder. • Patten, H. E. Heat Transfer in Soils. U. S. D. A.,Bur. Soils, Bui. 59, p. 30. 1909. 312 SOILS: PROPERTIES AND MANAGEMENT At first fijlance it appears peculiar that the heat move-ment through a soil, the mineral constituents of whichpossess a conductivity coefficient of about .01066, shouldbe raised by the addition of a liquid possessing a value ofK of about .00149, a conductivity about one-seventh ofthe soil minerals. The explanation of this as given byPatten is a lowering of the transfer resistance. He hascalculated that heat will pass from soil to water approxi-mately one hundred and fifty times more easily thanfrom soil to air. This being true, it is evident that asthe water is increased in any soil and the air decreased,the conductivity coefficient increases. It must be keptin mind, however, that as th
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