96 NEW YORK STATE MUSEUM 



great traffic-way. Great lines of canal boats pass in tow up and 

 down the river. With current and tide these are difficult to manage, 

 especially in attempted avoidance of these boring rigs placed adjacent 

 to the main channel. As a result some of these boring rigs were 

 wrecked after long time and much money had been spent on them. 



The margins of the river, however, came ultimately to be very 

 fu'-ly explored, and the general form of the gorge was outlined to a 

 depth of about 500 feet on each side. The central portion of the 

 channel, however, for a width of something like 1500 feet was still 

 unexplored, except by one boring which ultimately penetrated to a 

 depth of 765 feet without reaching bedrock. 



Such results aroused much suspicion in the minds of the engineers 

 responsible for this work and so much time had been consumed that 

 uncertainties of this section were considered to be the most question- 

 able feature of the whole aqueduct line between New York City 

 and the Catskill mountains, endangering, in the minds of some, 

 the success of the whole project. It was felt, therefore, that 

 complete information must be obtained in some other way. 



Enough confidence was placed in the geological conclusions and 

 evidence, however, to warrant continuation of the plans adopted 

 and the construciion already started at other points, to encourage 

 expenditure on permanent work at this crossing. The plan adopted 

 finally was to sink full-size working shafts on each side of the river 

 so that they could ultimately be used for the finished tunnel. After 

 sinking these to a depth of about 200 feet, rooms were cut in the 

 solid rock and diamond drills were set up in them, one on each side 

 of the river, at suitable angles to penetrate the ground underneath 

 the middle of the river. The first trial was made at an angle which 

 when projected reached a depth of 1400 feet at their intersection 

 under the middle of the river. The geological results were satisfac- 

 tory. Subsequently the drills were set up again at a flatter angle to 

 intersect under the middle of the river at a depth of 950 feet. This 

 also gave eminently satisfactory results, indicating the Storm King 

 type of granite for the whole distance in both sets of borings. 

 Surveys of the drill holes for deflection or deviation from the true 

 angle indicated comparatively little correction and these two sets of 

 borings were thereupon considered complete substantiation of the 

 geologic conditions expected, as previously interpreted, and sufficient 

 proof of the actual conditions to be encountered to warrant the 

 immediate letting of contracts and the beginning of construction of 

 the Hudson River pressure tunnel. 



