184 Reviews, — Jl Muck Manual for Farmers. 



part; geine has the least absolute weiijht, so that while a cubic foot 

 of sand weighs, in its common damp state, 141 pounds, clay weighs 

 115 pounds, and geine 81 pounds; hence garden mould and arable 

 soil weigh from 103 to 119 pounds. The more geine compound soil 

 contains, the lighter it is. 



Among the most important ])h}'sical characters of soil, is the pow- 

 er of retaining heat; this will be found to be nearly in proportion to 

 its absolute weight. The weight of soil determines with tolerable 

 accuracy its power of retaining heat. The greater the mass in a 

 given bulk, the greater is this power. Hence sands retain heat long- 

 est, three times longer than geine, and half as long again as clay. 

 Hence the dryness and heat of sandy plains. Sand, clay, and peat, 

 are to each other as 1, 2, and 3, in their power of retaining heat. 

 But while the cajiacity of soil to retain heat depends on the absolute 

 weight, the power to be warmed, another very important physical 

 character depends on four principal circumstances: first, the color; 

 second, the dampness; third, the materials; fourth, the angle at 

 which the sun's rays fall. First, color; the blacker the color, the 

 easier warmed. White sand and gray differ almost 50 per cent, in 

 the degree of heat acquired in a given time. As peat and the varie- 

 ties of geine are almost all of a black or dark brown color, it is seen 

 how easily they may become warm soils when dry; for, secondly, 

 dampness modifies the influence of color, so that a dry light-colored 

 soil will become hotter, sooner than a dark wet one. As long as 

 evaporation goes on, a difference of 10 or 12 degrees will be found 

 between a dry and a wet soil of the same color. Thirdly, the differ- 

 ent materials of which soils are composed exert but very little influ- 

 ence on their power of being heated by the sun's rays. Indeed, if 

 sand, peat, clay, garden mould, all equally dry, are sprinkled with 

 chalk, making their surfaces all of a color, and then exposed to the 

 sun's rays, the differences of their temperature will be found incon- 

 siderable. Color and dryness, then, exert a most powerful influence 

 on the capacity of soil to be warmed. 



Fourthly, the last circumstance to be noticed, is the different angle 

 at which the sun's rays fall. The more perpendicular, the greater 

 the heat. The effect is less in proportion as these rays, by falling 

 more slanting, spread their light out over a greater surface. But 

 this point, which seems external to soil, need not be enlarged on. 

 Now, the great fact to be observed in this relation of soil to heat, is, 

 that geine exerts the most marked influence. If soil heats quickly, 

 it is because it has a large proportion of geine. Does it cool quick- 

 ly.'' it is the geine which gives up heat quickly, referring here to the 

 soil in a dry state, the modification produced by dampness having 

 been already considered. 



The relation of soil to moisture and gas is not less important than 

 that of heat. All soil, exce|)t pure silicious sands, absorb moisture, 

 but in different degrees. Geine possesses the greatest power of ab- 

 sorption, and no variety of geine equals, in its absorptive power, 

 that from animal manure. The others rank in the following order, 

 — garden mould, clay, loam, sandy clay, arable soil. They all satu- 

 rate themselves with moisture by a few days' exposure. It is a very 

 interesting question, does soil give up this absorbed water speedily 



