Movements of Fluids Through Soils. 123 



144. Observed Flow of Water Through Sand Compared 

 With That Computed From the Effective Diameter. The ac- 

 curacy of the method described in (143) is best shown by 

 computing from the effective diameter of the soil grains 

 what the flow of water ought to be and then measuring the 

 flow of water to see how it corresponds. This has been 

 done and the results are given in the table below: 



When it is observed that the effective diameter of the 

 grains in these sands was found by measuring the flow of 

 air through one sample in one piece of apparatus and the 

 flow of water was measured through another sample and 

 in another piece of apparatus, and that the flow varies as 

 the squares of the diameters of the soil grains, it is clear 

 that the effective diameter has a very exact value so far as 

 the flow of fluids is concerned. 



