406 GEOLOGY OF THE SECOND DISTRICT. 



Gkey Sandstone. 



Towards the south part of Loraine, the shaly matter of the preceding rock has diminished 

 so much that tlie mass has become a sandstone. The sihceous matter, however, is somewhat 

 chano-ed, and it is of a lighter color than the sandy layers of the loraine shales. When the 

 sandstone is fully formed, it often contains thin layers of shale, but the siliceous layers pre- 

 dominate greatly over the slaty. Sometimes a fine green slate is insulated or inclosed in the 

 sandstone. As a whole, the mass is a uniform greenish grey rock, composed of grains of 

 quartz but little larger than a white mustard seed, and indeed the size is often too small to be 

 observed. • It appears similar to the ordinary stone used for grindstones — a pure sandy sharp- 

 gritted rock. 



As the loraine shales pass into this grey rock, the fossils diminish both in nimiber and kind ; 

 so that when the sandstone is fully formed, very few fossils remain. The Avicula demissa 

 and Strophomena nasuta were obtained in the quarries of this sandstone near Rome, but they 

 appear to be confined to the lower part of the rock. 



This mass appears, from its position, to be equivalent to the greywacke in the Hudson river 

 series. It differs considerably from it, being finer and more even grained ; and so far as 

 observation proves, it contains no beds of breccia or rubblcstonc. 



This rock is a valuable material for building ; and from its uniformity and evenness of grain, 

 and its freedom from hard uneven layers, it is not only adapted to a variety of purposes, but 

 is quarried at a small expense. 



The loraine shales, and the gi-ey sandstone overlying them, are entirely destitute of mineral 

 veins or beds, and even the ordinary earthy minerals rarely form a part of these masses. This 

 fact appears of some importance, when we compare the state and condition of these masses 

 with the same in the valley of the Hudson river. Here they are intersected remarkably with 

 veins of mineral matter ; and in this district it is that they are so remarkably disturbed, not, 

 however, by these mineral veins, for they are rather the consequence than the cause of dis- 

 turbance. The movements to which the masses have been subjected, fissured and rent the 

 strata ; and into these fissures and rents, mineral matter has been transported, forming thereby 

 what w-e term veins. 



The rocks of the south part of Jefferson have been subjected to but slight and inconsider- 

 able movements ; hence we find even a single stratum continuous over almost the whole 

 district, the mass as a whole dipping only gently to the southwest. In consequence, too, of 

 this horizontal position of the strata, we are able to ascertain their thickness ; whereas in the 

 Hudson river counties, the same rocks being deranged, it is difficult to ascertain this fact with 

 exactitude. 



In the Hudson river valley, there are occasionally imperfect ranges composed of a hard 

 siliceous rock, differing somewhat from the preceding as it commonly appears in Jefferson and 

 the adjacent counties. This siliceous mass occurs in a position analogous to the siliceous rock 

 at the north : it is underlaid by shales ; but in them there is a larger proportion of argilla- 



