GEOLOGY OF THE NEW YORK CITY AQUEDUCT 



193 



difference in the mineral make-up of 

 the beds fully as much as to dynamic 

 disturbances. The walls are generally 

 good. The fragments of core are not 

 much slickensided. In the schist this 

 is probably not as generally true. 

 There are much plainer evidences of 

 crushing movements in the schist. It 

 is a locality where one of the folds, 

 one well developed farther south, is 

 pinched out and there is rather gen- 

 eral crushing of the weaker strata. 



Depth of decay and perviousness. 

 As deep as borings have gone there 

 is occasional decay and broken ma- 

 terial and streaks that are. pervious. 



Final location. The condition of 

 bed rock, together with other consid- 

 erations led finally to the selection of 

 a site above the present dam. In 

 general the same features character- 

 ize this site. But the rock condition 

 is somewhat improved. On the whole 

 the new situation is a safer one. 



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