THE SOIL AND WATER 



things being equal, the smaller will be the amount of water 

 absorbed by the soil. The greater the quantity of water pre- 

 cipitated in a given period of time, the larger the proportion of it 

 will run off as surface water. The more rapidly the water runs 

 off, the more soil it carries along with it, and the more likely it is 

 to do damage by washing. 



Percolation. The rate at which water passes through the soil 

 depends upon the character of the soil and the treatment to which 

 it has been subjected. Sands allow water to percolate rapidly, 



3 Drain Gauges 



Each 7 feet 3- 12 in. x 6 feet = ^th acre area : 

 Respectively 20, 40, and 60 inches depth of soil, 

 collectors, each holding Drainage = 0*500 in. 

 Gauge-tubes graduated to .. .. 0-002 in. 

 Overflow tank to hold Drainaee. .=. 2- 000 ins. 



Fig- 35- Drain gauges, Rothamsted, England. 



and since they usually have a low capillary power, they often 

 suffer from drought. Some clays allow water to pass through 

 so slowly that they remain wet and heavy, do not warm up 

 quickly, and are often hard to work. The amount of water 

 which percolates may be decreased by increasing the water cap- 

 acity of the soil or subsoil. 



Drain Gauges. Drain gauges are used to study the gains and 



