38 SOILS 



ing each marble, has been left behind. So it is in the soil. 

 Each particle and there are billions in every cubic inch 

 seizes water as it passes down into the soil and holds 

 it so tight that only the highest heat in the drying oven 

 will entirely release it. Consequently, every field soil has 

 its many, many particles wrapped in a thin sheet or film 

 of water, and even the dry dust of the road holds fast to 

 its minimum quantity of water. 



The following table shows the water content of com- 

 mon field soils during a period of drought six weeks in 

 duration : 



Kind of Soil 5t; 



Clay road dirt 2.64 



Sand low in humus 8.34 



Clay excellent for grass 19.61 



Silt bottom produces eighty bushels of corn 12.30 



These same soils were sampled later in the same season, 

 after a period of rain of several days' extension. The 

 water content is shown in the table following : 



Per cent. 



Kind of Soil of Water 



in Wet Soil 



*Clay road dirt 29.08 



Sand 22.53 



Clay 31.96 



The passing of water through the soil. The rate that 

 water passes through the soil is governed by : 



1. The pore-space in the soil. 



2. The water channels formed by the arrangement of 

 soil particles. 



3. The amount of humus in the soil. 



It follows that great differences will be observed in the 

 passage of water through soils open soils permitting it 



*The road dirt was dried considerably by travel, which cut and opened 

 it a process of aeration. 



