232 Geology of the Highlands. 



Having been invited to perform some subordinate ser- 

 vices at tbe Military Academy at West Point, a very eligi- 

 ble opportunity was afforded for examining the rock forma- 

 tion in its immediate vicinity. The superintendant, Major 

 Thayer, Dr. L. Foot, Professors Douglass and Cutbush, 

 and myself, crossed the whole breadth of the Highlands, 

 during the month of May last, which is fourteen miles, and 

 continuetVour examinations so far as to become acquainted 

 with the adjoining rocks on both sides. As the river Hud- 

 son crosses this range of mountains from north to south, cut- 

 ting them down to their very base, each shore of the river 

 presents a very advantageous view of their strata. Accord- 

 ingly we coasted along each shore in a barge, taking speci- 

 mens wherever there was the least appearance of any 

 change. 



The following is the result of our investigations, given 

 without regard to the order of time in which they were 

 made. 



The middle portion of the Highlands for ten miles in ex- 

 tent, taking Buttermilk Falls (two miles below the military 

 academy) for the center, consists almost wholly of well 

 characterized gneiss, with alternating layers of granite. 

 There are also some beds and some alternating layers of 

 hornblende rock, included in it. 



These ten miles of gneiss are succeeded, both on the north 

 and south, by hornblende rocks; each about two miles in 

 extent. The true hornblende rocks sometimes alternate 

 with a kind of rock resembling gneiss, in which very dark- 

 coloured lamellar hornblende seems to be substituted for 

 mica. Such are the rocks constituting Butterhill and Dun- 

 dcrbergh. 



At the termination of the hornblende rocks, which is the 

 termination of the mountains both north and south, the 

 transition argillite commences. As far as w^e examined it, 

 we found it alternating with transition (or metalliferous) 

 limestone, and graywacke. The latter contains petrifac- 

 tions of terebratulites and orthocerites. 



We found, that the layers of all the rocks in the range, 

 whether primitive or transition, inclined toward the north- 

 west, from a vertical position. We could find no place 

 whereon to ftx, as the middle range, or granitic range, from 

 vhich to trace a succession of strata on each side, accord- 



