128 NEW YORK STATE MUSEUM 



feature, owe their present elevation chiefly to the resistance of this 

 conglomerate which serves as a protective member among the 

 formations. 



On the west side, the foothills of the Catskills form a part of 

 the cuesta developed by the erosion of Paleozoic sediments, the 

 inface coinciding with the escarpment along the lower Esopus and 

 Rondout valleys at this point. 



It is certain therefore that the drainage of the Rondout valley 

 before the Ice age differed materially from the present lines. A 

 stream, probably the original Rondout, followed near the western 

 margin of the valley and joined the Esopus as it emerged from the 

 Hamilton escarpment to turn northeast. Another which had cut 

 somewhat deeper occupied the central portion of the valley and 

 probably joined the Esopus at some point farther north — its lower 

 course is not explored. 



Practical questions 



The chief practical questions to be given as full answers as pos- 

 sible are: 



1 At what depth must the aqueduct tunnel be placed in order 

 to be everywhere in substantial bed rock with sufficient cover to be 

 safe? 



2 Where are the most critical places — those whose geologic 

 characters are such as to demand exploration? x\nd at the same 

 time which sections may be safely left without testing? 



3 What is the rock structure and condition? And are there rea- 

 sons for believing that the tunnel plan is not feasible at this point. 

 If so, where can a better one be found? 



4 What is the character of underground circulation of water? 



5 What formations will be cut at the different points and which 

 should be favored or avoided wherever possible ? 



From the fact that the present Rondout flows across solid ledges 

 at High Falls and at Rosendale from lOO to 200 feet above the 

 known rock floor of the preglacial gorge where explored it is clear 

 that the present course is entirely different from the original. The 

 Coxing kill, the third and most easterly of these streams is not so 

 much disturbed although it also is shifted. 



It is worth noting that the streams of this valley together with 

 the lower Esopus and the Wallkill river have become so completely 

 adjusted to the rock structure that they all flow up the larger 

 Hudson valley, of which all form a part, and join the master stream 



