1 6 NEW YORK STATE MUSEUM 



diminished in later years. Thus, in 1861 Delesse, a French geolo- 

 gist, by assuming a certain porosity for the strata and calculating 

 the amount of water required to fill the cavities, reached the con- 

 clusion that, were all this water to be spread over the surface, it 

 would make a layer 7500 feet deep.^ Estimates by others will be 

 found in the citations. They vary through the following values : 

 C. S. Schlichter 1902, 3000-3500 feet; C. R. Van Hise 1904, 226 

 feet; Chamberlin and Salisbury 1903, 800 to 1600 feet. 



The writer in 1901 endeavored to draw upon mining experience 

 and upon deep boreholes in discussing the ground water and con- 

 cluded that it extended as a rule to a depth of only 1000 to 2000 

 feet. If we allow 5 per cent for the voids in rock, this would mean 

 a layer 50-100 feet; or if 10 per cent, 100-200 feet. Ten per cent 

 i'< the extreme of voids in the most porous and 5 per cent is nearer 

 a fair estimate, but these two values are usually employed. 



M. L. Fuller of the United States Geological Survey in 1906, 

 after a very extended experience with holes drilled for water, in 

 his work upon the division of the Survey dealing with water supply, 

 concluded that the ground water would amount to a layer 96 feet 

 deep if it were spread out on the surface. At 5 per cent of cavities 

 in the rocky strata, this would go down about 2000 feet, or at 10 

 per cent about 1000 feet. T. Sterry Hunt determined the cavities 

 in the hard, white Postdam such as we have at Saratoga Springs to 

 lie between 1,39 and 2.47 per cent of the volume. Less metamor- 

 phosed varieties yielded from 6.94 to 9.35. (Chemical and Geologi- 

 cal Essays, p. 166, 1878.) These figures will help to make more 

 definite in our minds the amount of water of this kind with which 

 we have to deal. 



The meteoric ground waters in their migrations through the rocky 

 strata dissolve some mineral matter. The rain takes up a little 

 carbonic acid gas from the atmosphere and has to this extent its 

 solvent powers increased. It has also oxygen, nitrogen and other 

 gases in far less amount. The dissolved air is higher in oxygen and 

 carbonic acid and lower in nitrogen than is the ordinary atmos-, 

 phere. Potash, soda, lime, magnesia, and iron dissolve most readily 

 from the rocks. Silica is also taken in very small quantity, 

 as are several other rock-making components. On the whole, lime 

 is the most abundant and widespread of the dissolved bases, and in 

 ordinary spring waters the dissolved matter varies from a minimum 



♦ 



1 j\T. L. Fuller. Total amount of water in the earth's crust. Water 

 Supply and Irrigation Paper. U. S. Geol. Surv. 160. p. 59, 1906. 





