GEOLOGY OF THE THIRD DISTRICT. 



ST^E. 



1. POTSDAM SANDSI 

 Potsdam and Keeseville Sandstone. 

 (No. 1. Pennsylvania Shrtey.) 



This name is applied by Dr. Emmons to an important rock for thickness, extent, and for 

 ec(Hiomical purposes, which exists in the Second District, being the first mass going north 

 towards Lake Champlain, and further west, which rests upon the primary, the calciferous 

 sandrock being the next rock as to age ; and when together, they rest upon the sandstone. It 

 appears to form two distinct varieties in that district, one of which is found at Potsdam, the 

 other at Keeseville. This rock corresponds in position, etc. with No. 1 of the Survey of 

 Pennsylvania, and is common to New-Jersey, but in both these States it resembles the 

 Keeseville and not the Potsdam variety. 



In the third district this rock is rather rare, and confined chiefly to the northeastern part 

 of Lewis county, unless from change of character it is confounded with the calciferous sand- 

 rock. It presents two varieties in Lewis county, the locality not far from Lewisburg fur- 

 nace : a conglomerate of quartz, the fragments chiefly angular, with a few other fragments 

 of primary rock, forming the lower part of the mass ; and a sandstone above, exhibiting the 

 same characters in all respects as at Potsdam, being in very regular horizontal layers or 

 courses, from an inch to a foot or more in thickness, striped, of a reddish and yellowish 

 color, and of rather a coarse and loose texture. The sandstone appears in a few low insu- 

 lated ridges about two miles from the furnace, and also near Harrisville. 



Towards the Mohawk, the sandstone is found on the west side of Klipp lull, or the north 

 prolongation of the Noses, extending from the turnpike which goes to Johnstown, for about a 

 mile and a half towards the south road. Numerous small patches there exist, some of which 

 arc composed of two layers : one hard and whitish, the other friable, and colored brown and 

 red. They rest upon the primary rock in the usual unconformable manner, and were, no 

 doubt, once parts of a continuous mass destroyed with the former overlying rocks. 



The layers which occur between the primary rock and the calciferous, at the paper-mill on 

 Spruce creek, may be refcrcd to this rock. There the characters are somewhat different, 

 though the material is in a great measure the same, being a coarse grey rock, resembling in 

 parts, at first sight, a recomposed granite ; that is, a granite whose mineral constituents hacj 

 been separated and re-united again, without much if any change of place. The first layer is 

 about six inches thick, and contains fragments of vitreous quartz, which are likewise found in 

 some of the layers a few feet above. 



At the base of the well characterized calciferous mass on the Mohawk, below Canajoharie, 

 and on West Canada creek, below Middle villc, etc. there are a number of extremely hard 

 compact layers, whose fracture shows a glistening grain, as if composed of sand united by a 

 siliceous cement, as if the particles had come together by a partial softening and pressure. 



