GEOLOGY OP THE VICINITY OF LITTLE FALLS 81 



through the drift of the old, deeply filled valley east of the fault 

 line. There is no wide outlet valley into this through which the 

 preglacial Spruce creek could have come, and there must have 

 been once a col at the fault line, but this would have been cut 

 back, and the narrowness of the old valley would seem due simply 

 to the great hardness of the pre-Cambrian rocks in which it was 

 cut. 



The heavy drift filling for several miles east of the fault line, 

 as contrasted with the abundant rock outcrops on the west side, 

 shows that in preglacial times the fault was a more conspicuous 

 topographic feature than is the case now, and this by an amount 

 measured by the unknown thickness of the drift over the rock on 

 the east side. 



These old, buried valleys introduce an element of uncertainty 

 into the areal mapping of the rocks. For the most part they must 

 be ignored, since their location is unknown ; and, where they have 

 been located, the depth of drift is unknown, so that the precise 

 rock horizon beneath can not be told. Whenever they exist, the 

 areal map is likely to be somewhat in error in regard to the sur- 

 face rock. 



ECONOMIC GEOLOGY 



Building stone. The Lowville limestone has been the main 

 quarry rock of the district, and has had a considerable local use. 

 It is in general quite massive, not excessively jointed, of pleasing 

 color and quite durable. It has been more largely quarried at 

 Ingham Mills than at any other locality, though several other 

 quarries have been opened, the location of the principal ones being 

 shown on the areal map. The big Dolge mills at Dolgeville are 

 constructed of it, the locks of the Erie canal also and many other 

 smaller structures. It makes a most excellent building stone, 

 admirably fitted to supply all local necessities of the sort. It 

 has also been somewhat burned for lime and would seem the most 

 suitable of the local rocks for the purpose. 



The Beekmantown rocks have been somewhat quarried at Little 

 Falls, the lower layers being used, and slight openings have been 

 made elsewhere. While not as good as stone as the Lowville, this 



