7o 



THE TEXTURE OF THE SOIL 



[CHAP. 



Flow of Water through Soils. 



The freedom with which water will move through 

 soils under the action of gravity or other force will 

 depend not only on the pore space, but upon the 

 mean size of the channels formed between the soil 

 grains. King made some experiments with sands 

 graded by sieves and formed into columns 14 inches 

 long and 1 square foot in section, above which the water 

 was maintained at a head of 2 inches. He obtained 

 the following results expressed in inches of water 

 passing in twenty-four hours ; the second column gives 

 the number of meshes to the inch of the sieves which 

 respectively passed and retained the sand : — 



It will be noticed that there is a great diminution 

 in the rate of flow as soon as a soil containing small 

 clay particles is introduced ; of course, one of the 

 characteristic properties of clay is that it will not 

 allow any flow of water through it when it has been 

 puddled. In the puddled condition, the particles 

 constituting the clay are no longer aggregated, the 

 material is in its finest-grained condition, so that the 

 pore spaces between them must have become extremely 

 small. Not only is the flow diminished by the increase 

 of friction in the narrow channels, but in the case of 

 clay their dimensions have become so small that prob- 

 ably the contained water wholly within the range 



