I04 NEW YORK STATE MUSEUM 



direct evidence of it. The ancient valley is deep and probably 

 marks a line of displacements which can not be avoided, no matter 

 what route is chosen. The fault contact at the border of the High- 

 lands is not expected to prove troublesome as it seems very tight 

 at the exposures seen. The buried granite ridge (a continuation of 

 Snake hill) which underlies the western end is now known to come 

 within the limits of the tunnel and adds one more complication. 



Except for the fact that the ancient Moodna valley is deep and 

 filled with heavy drift that is unusually difficult to prospect, there 

 would seem to be no source of special trouble. It has no lines of 

 weakness that are not also present in the more northerly districts 

 and the tunnel has chances of crossing them under more advan- 

 tageous conditions without so much complication with the lime- 

 stone series as characterizes the New Hamburg group. 



h Hudson river. Among the Highlands group of crossings there 

 is considerable difference of structure dependent upon the exact 

 location of the crossing. The conditions that prevail may be sum- 

 marized as follows : 



(i) Storm King location. This is wholly in massive and gneissoid 

 granite. The rock is the most massive and substantial body of 

 uniform type found in the Highlands. The course of the river 

 indicates some weakness in that direction. This weakness may be 

 some minor crushed zone or even the jointing alone that prevails 

 throughout the exposed cliffs. But there is no direct evidence of 

 faulting, cutting the line and such crushing as may be encountered is 

 believed to have originated at such depth and under such conditions 

 as to cause no large disturbance. The freedom of this formation 

 from all bedding structures and natural courses of underground 

 water circulation on a large scale is an additional factor. There is 

 absolutely no other place, within the region, where the Hudson river 

 can be crossed from grade to grade in good ground of a single type 

 with so great probability of avoiding all large lines of displacement. 



(2) Little Stony point location. The conditions that prevail at 

 this point are similar to those that characterize the Storm King line. 

 The only known difference is in the considerably more shattered 

 condition of the granite, especially on the west shore at Crows Nest. 

 It is estimated that this crossing is less favorable by reason of just 

 this poorer condition of the rock and the somewhat greater yielding 

 to regional disturbances that it seems to indicate. 



(3) Arden point or West Point location. On this line the river 

 would be crossed in the gneiss series proper instead of in granite. 



