234 



NBW YORK STATE MUSEUM 



a trench of that length 1 mile wide and 660 feet deep. Of 

 course such an arithmetical calculation is solely intended to 

 show that enough material has been transferred in the Hudson 

 valley since the glacial period to more than fill to its present state 

 an old gorge such as the elevation hypothesis supposes to have 

 existed. 



As we have no direct evidence that the Hudson gorge is so 

 deeply excavated in the bed rock from West Point southward 

 through the New York Narrows the question of altitude of the out- 

 let at this particular stage under the conditions assumed must 

 remain locally undetermined. 



The width of the Narrows at the present sea level is approxi- 

 mately 1 mile and the banks are glacial materials. There is 

 naught in the deposits at the Narrows to render a former deeper 

 channel impossible. In fact, if we suppose the sides of the 

 channel wmere it is narrowest to slope down at an angle no 

 steeper than 30 degrees the slopes would meet at a depth of 

 over 1500 feet below the present sea level, a depth much in 

 excess of any required depth of the Hudson channel for the 

 drainage of waters from the Hudson-Champlain valley under 

 any of the conditions which are shown to have existed during 

 the retreat of the ice sheet. 



From a reference to the diagram plate 28, line G-H, it will be 

 seen that the outlet of the Fort Edward stage of Lake Vermont 

 at New York must now be submerged not less than 650 feet if the 

 view taken on page 102 is correct. 



DEFORMATION BY POSTGLACIAL FAULTS 



From the vicinity of Greenbush northward into Argyle there 

 is a belt of as yet unknown width in which the glaciated surfaces 

 of nearly vertical slates are disrupted by small faults with a 

 downthrow on the west, showing that in postglacial times the 

 land on the western side of the Berkshire hills has come to stand 

 relatively higher than that in the Hudson gorge and on the w^est 

 of the river. Further detailed work in the field is required to 

 make a quantitative statement concerning the amount of movement 

 on these small faults. I have not been able without this detailed 

 study to determine what role they may have played, if any, in 



