GEOLOGY OF SARATOGA SPRINGS AND VICINITY 1 59 



The generalized section of the rocks above the Little Falls 

 dolomite shown in the Natural Company's wells on South Broad- 

 way is as follows : 



140 feet Drift 



Soil and gray sand 25 feet 



Quicksand 45 feet 



Clay 20 feet 



Sand and gravel 50 feet 



r Shale 75 feet 

 118 feet Canajoharie shale J Alternating shale and 



(^ limestone 43 feet 



36 feet Amsterdam limestone 

 Little Falls dolomite 



The lowermost drift deposit at the locality is a heavy bed of 

 porous sand and gravel, capped by a twenty-foot thickness of 

 quite impervious Albany clay. When first entered by the drill 

 these lower sands were full of carbonated water, which had got 

 into the sand because of one or more natural springs coming up 

 through the shales and which had been retained there by the cover 

 of impervious clay. There was here a local reservoir of carbonated 

 water at a horizon 150 feet or more above the water in the dolomite. 

 At an early date in the history of the operations of the Natural 

 company this upper reservoir was pumped out and so remained. 

 When full it served to transmit the pressures of the ground waters 

 in the upper sands down to the rock waters beneath; when ex- 

 hausted of water the hydrostatic column was interrupted and this 

 pressure no longer transmitted, with the result that the normal 

 water head was lost, wbat amounted to a great cone of depression 

 was produced, and the water levels in the village and on the east 

 side of Coesa creek were affected. 



The presence of original carbonated water in this sand we take 

 to demonstrate the presence of outlets for the water in the shales 

 below. The carbonated water came up through the shales and 

 filled the sand reservoir under the clay. 



Since pumping ceased all over the district, as it passed under 

 State control, this pumped out reservoir in the sand has been 

 slowly refilling. When such refilling shall be complete and the 

 old ground water head thus restored, we look to see a demon- 

 stration of its eflfect upon the water levels in the lower grounds. 



The waters in the dolomite are no doubt following crevices for 



