﻿GEOLOGY OF THE NEW YORK CITY AQUEDUCT 259 



Each one is of great depth and indicates conditions decidedly- 

 different from the commonly accepted behavior for Manhattan 

 Island. 



Special interpretation of hole no. 202, on Hester st. near 

 Suffolk st. This is one of the very deep borings, on the pro- 

 posed distributary conduit, put down to investigate the character, 

 condition, and structure of the rock through which the proposed 

 tunnel would pass. 



A summary of the data secured, together with an interpretation 

 of conditions encountered follows: 

 1 Boring record (summary) 



Elevation of surface = +30.5 

 a Glacial drift 



0—123 f eet - Soil and various types of glacial drift 

 b Residuary matter of local decay 



130-150 red micaceous mud 

 c Disintegrating rock ledge too much decayed to furnish core 

 150-190 disintegration matter from pegmatite and associated 



ledge 

 190-214 quartz, hornblende, chlorite, mica, disintegration sand 

 d Decayed ledge rock capable of furnishing an occasional core 

 214-224 core — several pieces of coarse feldspathic, quartz 



mica rock 

 224-237 core — several pieces of core with much green mica 

 237-255 Cuttings and disintegration sands with much green 



mica 

 255-277 Pegmatite cuttings 

 277-305 Yellow clays and quartzose disintegration sands and 



cuttings 

 305-314 Core-pegmatite 



314-388 Gray quartzose disintegration sands 

 402-447 Coarse quartz and mica disintegration sands and finer 

 quartz-mica, hornblende-chlorite cuttings that do not look 

 badly decayed. The rather surprising thing is their failure 

 to core 

 447-463 Core — four pieces of schistose rock with white mica 

 and garnet, nearly vertical, and three fragments of pegmatite 

 464-497 Cuttings only 



