230 GEOLOGY OF THE SECOND DISTRICT. 



common, but in an amorphous state ; and tliere are also a few poor veins of iron, or iron 

 stone, in which the ore is in a state of peroxidation. 



The next mass of gneiss and hornblende reaches the lake shore about half a mile below 

 Port Henry. An interesting place for the examination of these rocks is at the termination of 

 the Potsdam sandstone, a few rods north of the furnace. A cove or small bay is formed by 

 the projecting point of the sandstone, in consequence of the destruction of a large mass of 

 primary limestone which intervenes between it and a high wall of gneiss. We find, first, the 

 potsdam sandstone on the shore ; secondly, passing round this point of sandstone, we find the 

 limestone ; and thirdly, the gneiss in a perpendicular precipice fifty or sixty feet high, against 

 which the limestone formerly reposed. Following down the lake a little less than half a mile, 

 we reach a place called Crag harbor. Here the gneiss and hornblende contain a vein of 

 magnetic oxide of iron, twelve feet thick. The dip of the rocks, together with the direction 

 of the vein, is changed from east to west, or in a direction opposite to the general inclination 

 of the primary on the east side of the main range of mountains. This dip is, however, still 

 found prevailing farther north, at the Walton, or as it is sometimes called the old Crown-Point 

 ore bed. 



The rock of this narrow range is more distinctly stratified than that of most of the other 

 localities upon the lake. The limestone of Port Henry, which has already been described, 

 appears to divide ; one branch terminates a little north of the furnace, while another wider 

 branch pursues a course still farther westerly, so that the range of gneiss which forms the 

 rock between Port Henry and Crag harboi passes between these two branches. 



The great body of gneiss of this county, however, is a wide belt which next succeeds, 

 and of which Bald mountain forms a conspicuous part. This belt is about nine miles wide, 

 and is an extension of the same mass which comes up from Warren county through Chester, 

 Johnsburgh, and part of Schroon. It presents all the varieties usual in primary rocks ; but 

 what is well worthy of special examination, is the gradual amalgamation of gneiss with hy- 

 persthene rock. Contrary to the common representations in elementary works on geology, 

 there is no passage of the latter beneath the former, so far as surface indications show ; and 

 the latter cannot therefore be said to rest upon the former, but they are imperceptibly incor- 

 porated with each other. This range pursues a northeasterly course, and terminates along 

 the shore of the lake in steep high walls, which are often perpendicular. Such is the case 

 at the high rocks nearly opposite Basin harbor. The main portion of this range terminates at 

 Spht-rock ; or it may be called the middle portion, as a branch still more westerly appears 

 one mile west of Weslport, and finally terminates in Willsborough upon the lake. 



The main range of gneiss and hornblende is important, in consequence of furnishing so 

 many veins of iron ore : it forms a metalliferous district, and some of the veins are excellent 

 for the quality of the iron they produce ; some portions of it are well adapted for castings, 

 while others form a tough malleable iron. 



Although I have given the bounds and limits of the gneiss and hypersthene rock with as 

 much precision as if they were strongly marked, still tiiis is not strictly correct ; for, thongh 

 the latter is often well developed along this line, there arc yet many examples of gneiss and 



