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 ]\Ianhattan 

 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 : 

 I Boring record (suniDiary) 



Elevation of surface = -^30.5 

 a Glacial drift 



0-123 feet. 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 liner 

 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 



