﻿GEOLOGY OF THE NEW YORK CITY AQUEDUCT 26l 



tween Madison on the east and the Bowery on the west belongs to 

 the Fordham than at first supposed. This very much improves the 

 outlook for safe and easy construction. 



The second one, i. e. the finding of limestone at 531 feet is prob- 

 ably an interbedded limestone bed and not a part of the large In- 

 wood formation. 



The third point, i. e. the finding of schists and gneisses in 

 the same hole introduced more difficulty of interpretation. This dif- 

 ficulty was considerably increased by the fact that the ledge is so 

 badly decayed and so broken up in the drilling that no typical ma- 

 terial for identification could be secured in the upper portion. There 

 is no doubt as to the finding of Fordham in the lower portion. 

 Later explorations support the conclusion that the whole belongs to 

 the Fordham series. 



When this boring was first made, the schistose portion was 

 thought to be the Manhattan formation, and the limestone could 

 then be Inwood. Subsequent exploratory work at other points has 

 proven that the Fordham itself shows such schistose facies rather 

 commonly where associated with the interbedded limestones. This 

 is now the accepted interpretation for the whole eastern half of the 

 Lower East Side belt covered in the present discussion. 



There probably is some faulting. But whether the fault 

 plane dips east or west and how much the total movement is 

 has not yet been developed. This, however, is a more vital 

 question than would at first appear, for if the fault dips east 

 the ground to the west of it is probably all Fordham of good 

 quality and will be easily explored, whereas if the fault plane dips 

 to the west the whole west side for several blocks is much more 

 uncertain. It is probable that the majority of the rock lying west 

 of it will be of better quality than found in this hole. 



Interpretation of hole no. 207 (old no. 51) 

 On Henry street midway between Clinton and Montgomery 



Drill boring no. 207 has been put down to a depth of more than 

 655 feet (approximately -633). The material is of unusual quality 

 and behavior and therefore seems to require special study with a 

 view to reaching a correct interpretation. The most essential points 

 of the drill record are given below. 



