﻿REPORT OF THE DIRECTOR IQIO 1 5 



had been worked out. The matter referring to the Tarrytown dis- 

 trict is being put into form for publication. 



In previous reports reference has been made to a cooperative, 

 undertaking with the New York City Board of Water Supply in 

 the elucidation of geological problems encountered in explorations 

 along the line of the Catskill Aqueduct. Our representative in this 

 work has been Doctor Berkey, whose report on studies from the 

 earlier exploratory work On the Geology of the A T ezu York City 

 (Catskill) Aqueduct is now printing. During the past year great 

 progress has been made in actual construction in this important 

 engineering work. Many shafts and tunnels penetrate portions of 

 formations that have never before been exposed to observation. 

 The opportunities for collecting data of much value in a study of 

 this region have been exceptional, but immediate advantage must 

 be taken of them. 



A four-mile tunnel is almost completed beneath the Rondout 

 valley, and similar ones, penetrating the Shawangunk mountains and 

 beneath the Wallkill valley, have reached about the same stage. 

 Smaller parts are finished at several other points farther south. 

 Interpretations that had been made from the evidence of surface 

 outcrops and drill borings are now being exposed to direct com- 

 parison with the facts revealed in the underground workings. These 

 later and final results will be made available in some suitable form 

 upon the completion of the work. 



Exploration is still in progress on the Hudson river between 

 Storm King and Breakneck mountains. The deepest boring in the 

 middle of the river has penetrated river silts and drift filling to a 

 depth of 751 feet below the river level without reaching bedrock. 

 Inclined borings have been made from shafts at either side of the 

 river and have advanced far enough to cross beneath the center of 

 the channel. Each boring is about 1500 feet long and a survey of 

 the holes indicates that they cross at a depth of approximately 950 

 feet below river level. It is certain therefore that the preglacial or 

 glacial channel bottom lies somewhere between -751 and -950 feet. 

 The drill cores indicate sound rock throughout. 



The depths to which water circulation has accomplished extensive 

 solution or decay is a related matter of special interest at several 

 other points. In the Rondout valley the pressure tunnel has encoun- 

 tered several large clay seams, several feet wide, at a depth of 150 

 feet below present sea level. These seams are clearly fillings of 

 former solution channels in the Helderberg limestones. They indi- 



