304 GEOLOGY OF THE THIRD DISTRICT. 



lost beneath the flat surface of the Utica slate, the line of continuity on that side being un- 

 broken. Where the whole series is complete, the Utica slate forms the upper part of the 

 uplift, and appears also by the side of the wall of rock at the east, curving firom a flat surface 

 upwards, and either reposing against the gneiss or a higher rock. 



These uplifts have been thrust through the Utica slate, subsequent to the excavation of a 

 valley scooped from that rock and the higher ones, the rock extending from the west of Utica 

 into the first district. 



The facts upon which this opinion is founded, are these : The direction of the hills to the 

 south of the valley, which is also uninfluenced by the uphfts ; the great breadth of the valley 

 between the upUfts, and at the upUfts, especially on the east side of the gap at Little-Falls ; 

 the manner in which the high alluvial banks are disposed, which border the river valley ; the 

 composition of the alluvial, being luiiform throughout the course of the river ; and a corres- 

 pondence in the height of the alluvial banks. There are other facts, but not so obvious as 

 those mentioned. 



Between Mindenville and the county line opposite Manheim village, there is proof that an 

 ancient river bottom existed anterior to the one in which it now flows. For a mile or two in 

 length and three-fourths in breadth, the surface is a plain, thickly covered with rolled stones 

 disposed in all respects like those in a river bottom. They are of the usual kind, grey and 

 red sandstone and primary rock, suitable for paving, and also of lesser size. The enclosures 

 there are formed of them. The surface is like one of the same kind below the Noses, Jind 

 another to the south of Herkimer village, the three being on the same side of the river. It 

 is not easy to explain the cause of their existence, without the removal of the uplifted masses 

 which form the barriers of the ancient valley. 



These upUfts of the Mohawk, from their limited extent — from no derangement accompa- 

 nying them, other than is obviously inteUigible — from their well-defined configuration — from 

 being one of the terminal or extreme western limits of those great derangements whose cause 

 has acted with so much violence along the whole of the Atlantic region of the United States, 

 and from a number of highly interesting phenomena, are admirably calculated to instruct the 

 student of geology in the knowledge of some of the causes of the varied appearance of the 

 surface of the earth, and the derangement of its strata. At the junction of the uplifted rocks 

 with the slate which forms the base of the valley, exudations of iron ore exist at several points, 

 and in one instance a regular vein of lead ore, with a dyke interposed between it and the up- 

 lifted rocks. These are illustrations upon a small scale, of an action whose results are pro- 

 portional, all things else being the same, to the magnitude of disturbance. 



From the fact of the northern part of the uplifts being more raised than the south part, and 

 from their inclination to the west, giving a southwest dip, it is obvious that the cause which 

 raised the whole mass of the third district operated in the same direction with the one which 

 produced the local uplifts ; rendering it probable that the two cfiects were simultaneous, the 

 result of a general and a partial action, as in the movements of an ocean. 



These uplifts, though they have deranged the surface of the country where they exist, have 

 in other respects been a benefit. It is obvious from the inspection of the geological map, that 



