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Total Water in the Ground. - - The question of the amount of 

 free water in the ground is of much interest to drillers and those 

 seeking supplies. By free water is meant water in its ordinary 

 liquid form. It does not include the chemically combined water 

 of certain minerals and rocks, but is the water that occupies the 

 pores, joints, solution passages or other openings. 



Several attempts have been made in both Europe and America 

 to estimate the total amount of such water in the earth's crust, 

 but with varying results. Delesse, in France, estimated the 

 amount as sufficient to make an envelope of water 7500 feet in 

 thickness. Slichter, in America, placed the amount as equivalent 

 to a sheet 3000 to 3500 feet thick. Van Hise's estimate for the 

 continental areas was a sheet equivalent to 226 feet, while 

 Chamberlin and Salsbury estimated the amount as equivalent to 

 a layer 1600 feet in depth. In all four cases, however, the esti- 

 mates were based wholly on certain theoretical assumptions, 

 several of which are now known to have been incorrect. An esti- 

 mate by the writer, based on a wide study of the actual con- 

 ditions in thousands of wells and scores of mines, combined with 

 revised theoretical data, places the estimate at a little less than 

 IOO feet for the equivalent thickness of the ground water body in 

 the earth's crust as a whole. It must be understood, however, 

 that locally the amount is likely to be several times that stated, 

 while elsewhere nothing but practically dry rocks will be pene- 

 trated from the surface downward. 



Methods of Absorption. -- The amount of water which enters 

 the rocks or other materials by direct absorption varies greatly 

 with the nature of the materials. The amount absorbed by the 

 porous beds of sands and gravels that occur along stream valleys 

 and along lake shores and the coast is very large. In some 

 regions, as in portions of Cape Cod and Long Island, there are 

 practically no surface streams, the water being permanently 

 absorbed by the soil as soon as it falls and carried to the sea by 

 underground drainage. 



Next to unconsolidated deposits the rocks which present the 



