OF.OLOGY OF THE WEST POINT QUADRANGLE, NEW YORK 95 



aj)|;arent that the actual bottom of the Hudson at its deepest point 

 was not determined at all. It was also apparent that with the very 

 deep gorge extending out to sea for 75 miles, measuring approxi- 

 mately 4000 feet deep on the submerged margin of the continental 

 shelf, a good opportunity was presented for a much deeper Hudson 

 gorge in the district under study. It was soon found also that at 

 no place along the Hudson between Albany and the sea was the depth 

 fully determined. Explorations therefore had to be undertaken. 

 These involved exploratory borings in the river and, ultimately, 

 inclined borings from shafts located on either side of the river. 



From outside sources of information and especially from wash 

 borings put down in the vicinity of New Hamburg it was estimated 

 that the depth to the rock bottom of the river would be more than 

 200 feet, but relying on the belief that the 300-foot depth reported at 

 New York was reasonably correct, it was argued that the river gorge 

 should not be any deeper than this and probably not so deep at the 

 Storm King crossing. It was somewhat of a surprise, therefore, 

 when one of the early borings in the river considerably to one side of 

 the center, penetrated a great variety of materials, chiefly bouldery 

 and gravelly drift, to a depth of 500 feet before striking rock. 

 Great difificulty was encountered in putting down these test borings. 

 Seldom . has an exploratory investigation been undertaken under 

 more discouraging conditions. Because of the tidal flow and river 

 current, the machines had to be perched on platforms or fastened to 

 the casings that were established as the first part of the boring opera- 

 tion, while the power and other equipment was located on scows 

 anchored beside them. 



The most difficult of all ground to penetrate is just such mixed 

 structural materials as was found at this place. It is necessary in 

 such case to start with a very large diameter casing, driving it as 

 far as conditions will allow, and then, when halted by material which 

 can not be further penetrated, introduce some form of churn drill or 

 similar device which can be worked inside of the first casing tube. 

 This permits additional progress through boulders or other obstruc- 

 tions, but at the same time reduces 'he size of the bore. As soon, 

 therefore, as material is encountered which slumps, it is necessary 

 to put down another protecting casing inside the first and proceed 

 with it in the same manner as far as it will go. This is a time-con- 

 suming and very expensive process and where very deep borings 

 have to be made under such conditions, many additional difficulties 

 serve to complicate the problem. For example, the Hudson is a 



