22 NEW YORK STATE MUSEUM 



direction as the ancient mountain-building- pressures which pro- 

 duced the eastward dipping cleavage. If the case at Troy be 

 taken as a clew, the faults might be expected, as pointed out 

 above, to occur most abundantly and most pronouncedly on the 

 overturned flanks of the synclinal axes in the zone of strain in 

 which an overthrust normally begins in folded strata. 



From the data so far at hand it can not be assumed that the 

 measured rates of dislocation within any given horizontal dis- 

 tance of exposure continue beneath the drift-covered portions 

 of the field, and consequently the attempt to determine the rela- 

 tive uplift of the surface at the base of the mountains, as com- 

 pared with the level at the shore of the Hudson, must give an 

 uncertain, probably minimum, measure which will vary also in 

 amount from north to south along the extension of the phe- 

 nomenon. Even this possible difference of level between the 

 eastern and western limits of the faulted zone may be only 

 apparent, the faulting being effected by a rotational movement 

 of the slices of rock between the fault planes. A steepening" 

 of the high eastward dip of the cleavage would produce the 

 observed local result without changing the attitude of the sur- 

 face as a whole. 



The exposures in eastern New York are so near tide level 

 and bench marks accurately determined that it would appear 

 desirable to make precise determinations of the level of certain- 

 points along the eastern and western limits of the zone of 

 faulting with the view of comparing the measurements with a 

 second series of observations made after some lapse of time for 

 the purpose of ascertaining the nature of the movement if it is 

 still in progress. For the same reason observations might be 

 made at particularly favorable sites where the faults are well 

 exposed through some such means as the perhaps too delicate 

 bifilar pendulum affords so as to obtain within a few days an 

 indication of the tilting if it is going on at the present time. 



There are no observations as to the depth to which the faults 

 affect the slates. I am not aware that the faulted belt is one 

 peculiarly liable to earthquake shocks at the present time. 



In conclusion, it may be stated that the postglacial faults 

 appear to lie in a zone of overthrusting extending along the 

 western base of the Taconic and Green mountain uplift of folded 

 structures from near the Highlands of the Hudson into the 

 province of Quebec, with at present notable gaps in the obser- 



