14 NEW YORK STATE MUSEUM 



been discovered. It is true that the faults in the bed rock are 

 Hmited to narrow belts and that the houses in question may lie 

 outside of these belts. Nevertheless, both from the reversed 

 character of the movements in the cases of the houses which have 

 settled and from the great amount of the movement, it seems 

 that there is no warrant for holding that the displacements in 

 the houses are due to the movements in the bed rock. It follows 

 from this general conclusion that the postglacial fractures in this 

 vicinity may be and probably are older than the settlement of 

 Troy. 



It will be observed that the postglacial fractures in the bed 

 rock, on account of having their downthrow on the western side 

 of the fault plane, have increased the steepness of slopes inclined 

 to the west. On the other hand, the clays of this district in 

 themselves constitute a mass which under certain conditions of 

 structure and access of water are competent from their sliding 

 movement to produce all the displacements in houses observed 

 in Troy and vicinity. 



Faults in Rensselaer. In 1900, I found small postglacial faults 

 cutting the slates on High street near 3d avenue in Rensselaer. 

 Within the space observed there was a downthrow of 5 inches 

 to the west, the surface being inclined also originally in that 

 direction. Farther south where the road going to East Green- 

 bush ascends the east ibank of the Hudson gorge, a small post- 

 glacial fault was seen on a glaciated surface overlain in the cut 

 by till. The downthrow was to the west. 



At one of the localities in this vicinity, I recollect finding an 

 instance in which a narrow strip of slate stood up between two 

 parallel planes of faulting. This is the only case in which in 

 eastern New York I have observed a relative downthrow to the 

 east. 



Faults in Defreestville. It was at Defreestville in the season 

 of 1900 that my attention first became directed to the post- 

 glacial bed rock faults. A brief note of this locality is to be 

 found in my report on the ancient water levels of the Hudson 

 and Champlain valleys.^ Defreestville lies opposite Albany on 

 the east bank of the Hudson at the inner limit of the upper 

 clay-covered terrace and nearly on the boundary line between 



IN. Y. state Mus. Bui. 84. 1905. p. 234-36. 



