296 SOILS: PROPERTIES AND MANAGEMENT 



ing with various grades of quartz sand he obtained 

 practically identical specific heats with the various sepa- 

 rates : 



SPECIFIC HEAT OP VARIOUS GRADES OF SAND AS FOUND BY 



ULRICH 



Diameter of Sands in Millimeters Specific Heat 



2- 1 .1912 



1-.5 .1908 



.5-.25 .1922 



.25-171 .1919 



.171-.114 .1919 



.114-.071 .1904 



.071-.010 .1890 



It is evident, therefore, not only that texture has no 

 very great direct effect on specific heat, but also that 

 the controlling factor in the data already quoted is the 

 composition of the soil. The predominate minerals 

 found in soils possess a specific heat of from .180 to .220. * 

 This rather narrow range would normally be still further 

 lessened, since an average soil is a complex of the 

 different minerals. Humus, then, possessing a -specific 

 heat of about .5 must, when added to any soil, in- 

 crease markedly its thermal capacity and would un- 

 doubtedly be the determining factor in weight specific 

 heat of the mixture. 



213. Specific heat based on volume of soil. Under 

 normal conditions, however, the soil contains a consider- 

 able amount of pore space, and different soils would 



1 Ulrich, R. Untersuchungen liber die Warmekapazitat 

 der Bodenkonstitenten. Forsch. a. d. Geb. d. Agri.-Physik, 

 Band 17, Seite 1-31. 1894. 



