456 



THE PRINCIPLES OF SOIL MANAGEMENT 



difference from that of water, has an important prac- 

 tical bearing. Drainage owes one of its largest beneficial 

 effects to this fact. 



Warington quotes from Lang the following table 

 of specific heat of soil constituents. 



Table LXX 



Water 



Ferric oxide 



Calcium carbonate 



Magnesium carbonate 

 Quartz, orthoclase, granite 



Humus (peat) 



Clay ... 



Relative specific heat of 



Equal weights Equal volumes 



1.000 

 0.163 

 0.206 

 0.260 

 0.189 

 0.477 

 0.233 



1.000 

 0.831 

 0.561 

 0.754 

 0.499 

 0.587 

 0.568 



In the above table, the specific heat of equal vol- 

 umes is more nearly representative of field conditions 

 than is that of equal weights. On this basis, dry soil 

 has about one-half the specific heat of water; that is, 

 a given amount of heat would raise a mass of soil to 

 nearly twice the temperature that it would the same 

 volume of water. 



326. Color of the soil. A dark-colored soil absorbs 

 heat much more rapidly than does a light-colored one, 

 and therefore warms up more rapidly. The effect of a 

 thin layer of carbon-black and chalk on the tempera- 

 ture of dry, fine sand, one inch below the surface, 

 when exposed to the sun in thick wooden boxes, is 

 shown in the following table: 



