CLAflSIFTCA nOfl OF SOIL8 75 



the plow or other implement of cultivation moves 

 through them easily. A heavy soil II 00X6 that ifl more 

 difficult to cultivate: it is stiiT and offen more I 

 ance to the plow or spade than a Light soil. The so- 

 called light soil, as a rule, contains much saml. and is 

 by weight the heayiest of all soils. The heavy soils 

 contain much clay, which ifl lighter than Band. Soils 

 that contain much organic matter, peaty Boila, ."*• often 

 li^'ht in hoth senses of the word. The following figures 

 approximately the weights of the different soils: 



Dry Sand. ... !<>n to 120 pound- percubic foot 



Loam 00 to 100 pounds per cubic foot. 



Clay 78 to 80 pounds per cubic foot. 



Peat, etc 30 to 50 pounds per cubic foot, 



77. Warm and Cold Soils. — According to their power 

 of retaining the ran'fl heat, soils are called WARM Of 

 COLD. The amount ol heat absorbed \arie> greatly in 

 different soils, and depends on several conditions, but 

 may be to some extent regulated by careful ,-ultivat i<>n. 

 Plants for their proper development require a certain 

 amount of heat in the soil. Bead will m>t >prout until 

 the soil has become warmed to the required tempera- 

 ture, and mo>t farm CTOpfl attain their most p 

 development only in warm soils, Controlling, as far a> 

 possible, the amount of heat absorbed by soils is then 

 a matter of the greeted importance, and with thi 

 in view it Ei well to consider some of tin* conditions 



which influence the amount of heat in tofla. 



Water has the greatest influence on soil temperature; 

 it is, in fact, the great temperature regulator of the 



