RELATIONS OF SOIL TO HEAT 



SPEOIFIO GKAVITY AND SPECIFIC HEAT OP 

 SOIL CONSTITUENTS. 



Thus the same quantity of heat will raise 1 lb. of 

 water and 5 lbs. of chalk or quartz sand to the same 

 temperature ; and during cooling, 1 lb. of water will 

 give out five times as much heat as 1 lb. of chalk or 

 quartz. Or, looking only at the solid constituents of 

 soil, the same amount of heat will raise 3 lbs. of humus 

 and 8 lbs. of quartz to the same temperature. 



The specific heat of different soils is, from a practical 

 point of view, best shown by the quantity of heat 

 required to raise equal volumes or depths to the same 

 temperature. With dry soils, including only hygro- 

 scopic water, about three cubic feet would be heated by 

 the sun to the same degree as one cubic foot of water. 

 In this condition there is little difference between 

 different soils ; a dry peat will consume the least 

 heat, and a dry clay the most. When, however, soils 

 become wet great differences appear. In a freshly- 

 drained condition, a coarse gravel or sand will warm 



