ANCIENT WATER LEVELS OP CHAMPLAIN-IIUPSr>N VALLEYS 235 



the tilting of the old water levels in the upper Hudson valley. 

 The following note on the faults at Defreestville shows that these 

 movements ma^' assume some importance in the solution of the 

 problem when their distribution has been accurately determined. 



At Defreestville east of Albany a few rods from the road 

 corners on the southeast road from that place there may be seen 

 in the gutter well glaciated rock surfaces broken into small 

 step faults each with a downthrow from a fraction of an inch 

 to as much as 3 inches on the Avest. In a horizontal distance 

 of 12 feet I measured a westerly downthrow of 1 foot vertical. 

 It is probable that this zone of displacement has narrow limits 

 but the local rate is as great as 440 feet change of level to 1 mile 

 horizontal. The fact that the same small faultings occur on the 

 bank of the river at Greenbush is indicative of a measurable 

 change of local levels in the terrace of this part of the valley. 

 No allowance has. been made for these movements in the present 

 report. 



Mather^ reported the existence of similar faults in slate rocks 

 in Copake and Ancram. He mentions a locality near the end 

 of WinchelFs mountain and not far from the base of Mt Wash- 

 ington on the road from Copake to Boston Corners. He further 

 cites Professor Merrick as having seen other examples, i^ mile 

 west of Long pond in Clinton, in which the surface was displaced 

 from 2 to 3 inches. 



What appears to be a nearly north and south fracture with 

 3 or 4 feet throw with broken blocks of rock thrown into a narrow 

 fissure occurs on the lake side of Trembleau mountain just south 

 of Port Kent station. The downthrow in this instance is on the 

 east in the direction of the lake valley. On Mt Monnoir near 

 St Johns, Quebec, on the eastern side near the summit, similar 

 evidences of fracturing appear with large inthrown blocks of 

 rock from the sides. One of these cases was within the zone of 

 wave action during the submergence ; certainly that at Port Kent 

 was within the zone of marine action. Wave action frequently 

 opens small chasms in jointed and fractured rock but in a 

 regressive movement of the sea it would hardly choke up such 

 openings with large blocks from the sides in tumultuous disorder. 



^Mather. Geol. N. Y. 1st Dist. 1843. p.156-57. 



