GEOLOGY OF SARATOGA SPRINGS AND VICINITY 1 55 



reason entirely apart from amount of throw. The significant 

 feature of the fault is that shales are the surface rocks on the 

 downthrow side, and are continuously at the surface to the east 

 for many miles. 



Away from the fault the drill discloses carbonated water under- 

 ground only in territory where shales are the surface rocks, terri- 

 tory to the east of the fault. No doubt, in this shale-covered 

 region, the waters have wider distribution than the drill has yet 

 shown. But there is no reason to believe that there will be any 

 disclosure to conflict with the statement that the water is restricted 

 to shale-covered territory, in which the impervious shales prevent 

 its ascension to the surface ; that such territory has its western 

 boundary at the Saratoga fault and that the water can and does 

 make its way to the surface along this fault ; and that carbonated 

 water has never been found on the west side of this fault and 

 will never be found there. ^ East of the fault the waters are im- 

 prisoned under the shales. The Saratoga fault furnishes the line 

 for escape of the water simply because it happens to be the par- 

 ticular fault which terminates the shales on the west. 



The rock which acts as the reservoir for storing the water is 

 the Little Falls dolomite. Invariably the drill discovers it in that 

 rock. Occasionally, owing to local conditions, the drill reached 

 water in the Amsterdam limestone, and was not sent down into 

 the Little Falls beneath. But the evidence is clear in such cases 

 that the water had worked its way up into the limestone from 

 the dolomite along some fissure. Only one well in the whole region, 

 the Hathorn bore, has been carried through the dolomite. This 

 well discovered water in the Potsdam underneath. Unfortunately 

 no sample of this water was saved and analyzed, but Mr Hathorn's 

 statement concerning it is that it was water of the general Sara- 

 toga type, but very weakly mineralized ; hence the well was sealed 

 far above it and only water from the dolomite admitted. In gen- 

 eral, the dolomite is not a porous rock. Certain of its beds have 

 a calcite cement and weather porous : but in the drill cores they 

 all seem solid and impervious, and it seems probable that the water 

 supply in the formation is all contained in cracks and fissures, in- 

 stead of in porous layers. 



1 The Ainsworth well in Saratoga is a possible exception to the above state- 

 ment since it may be located a few feet west of the fault line. Tt is, how- 

 ever, practically on the fault line. 



