232 NATUEE AND PROPERTIES OF SOILS 



rate of cooling in autumn, drainage influences, and like phe- 

 nomena. 



Specific heat data from different investigators do not show 

 the agreement that might be expected.^ This is probably due 

 (1) to inaccuracies in the naming of the soils used, (2) to 

 difference in methods, and (3) to difficulties in technique. 

 Everything considered, the following table from Ulrich ^ dis- 

 plays in a suitable way the important specific heat phases: 



Table XL VII 



VOLUME OF SPECIFIC HEAT OF 



SOIL 



Soils 



Weight 

 Volume 



Volume 

 Specific Heat 



Sand 



Clay 



1.52 



1.04 



.37 



.2901 

 .2333 



Organic matter 



.1639 







It is evident that specific heat is partially governed by the 



organic matter of the soil and partially by texture and strue- 



speeifie heat is the number of calories necessary to raise the temperature 

 of one cubic centimeter of the substance one degree. In the ease of 

 soil, weight specific heat may be changed to volume specific heat by 

 multiplying it by the volume weight, since volume weight is the weight 

 in grams of one cubic centimeter of dry soil. 



^ The following weight specific heats from Lang,* Patten t and Bou- 

 youcosl are interesting: 



Lang Patten Bouyoucos 



Coarse sand 198 Sand 185 Sand 193 



Limestone soil. . , .249 Sandy loam 183 Gravel 204 



Organic soil 257 Loam 191 Clay 206 



Garden soil 276 Loam 194 Loam 215 



Peat 477 Clay 210 Peat 252 



* Lang, C, T^ber Warme Capacitat der BodenconsUtuenteii; Forsch. a. 

 d. Gebiete d. Agr.-Phys., Band I, Seite 109-147, 1878. 



t Patten, H. E., Heat Transference in Soils; U. S. Bept. Agr., Bur. 

 Soils, Bui. 59, p. 34, 1909. 



t Bouyoucos, G. J., An Investigation of Soil Temperature; Mich. Agr. 

 Exp. Sta., Tech. Bui. 17, p. 12, 1913. 



^Ulrich, R., TJntersuchungen uber WdrmeTcapoBitdt der BodenJconsii- 

 tuenten; Forsch. a. d. Gebiete d. Agr.-Phys., Band 17, Seite 1-31, 1894. 



