132 



Physics of the Soil. 



In this table the third foot in each case is more or less 

 sandy and for this reason shows' percentagely less water 

 than the soil above. It will be seen that the surface foot 

 of sandy loam contains the smallest per cent, of water and 

 the humus soil the largest, but on account of the differences 

 in dry weight of these soils their water contents are more 

 nearly equal than they appear, the sandy loam containing 

 about 16 Ibs., the clay loam 18 Ibs. and the humus soil 

 26 Ibs. per cubic foot. Expressed in inches the amounts 

 stand 3, 3.5 and 5 inches nearly. 



158. Maximum Capacity of Undisturbed Field Soil. In 

 the table below are given the amounts of water which com- 

 pletely filled the first five feet of undisturbed field soil, as 

 determined by driving 6-inch metal cylinders one foot long 

 into the soil and, recovering them, covering the bottoms 

 with perforated covers and then placing the cylinders un- 

 der water until the pores became completely filled. 



Table showing maximum capacity of undisturbed field soil 

 for ivater. 



In this case it is seen that two feet out of five feet of the 

 soil was open space which could be occupied with water. 



159. Maximum Capillary Capacity of Soils for Wrier. 

 The amount of water which may be retained in soils by 

 capillarity is greatly influenced by the distance of the soil 

 above standing water in the ground and by the frequency 

 and amount of rainfall. The cylinders of soil referred to 



