226 



GNEISS. 



Primary Stratified Rocks. 



After presenting this general outline of the range 

 of the primitive formations in the United States,, 

 and the unstratified rocks in particular, it will be 

 proper to devote a few remarks to the considera- 

 tion of -the primary stratified rocks. 



Gneiss.* — The oldest of these, and one that occu- 

 pies more surface in New-England than any other, 

 is gneiss rock. Indeed, it is one of the most ex- 

 tensive formations in all primitive countries. With 

 the same mineralogical constitution as granite, and 

 lying next to it, with its ingredients arranged in a 

 stratified form, it has evidently been produced by 

 the disintegration of that rock, and its structure 

 modified by various causes. There are many vari- 

 eties of this rock, according to its structure and 

 composition, as granitic, lamellar, porphyritic, tal- 

 cose, &c. Many of the mountain ranges and hills 

 of the New-England States are composed of gneiss, 

 such as the White Mountains of New-Hampshire, 

 some of the Green Mountain ranges of Vermont, 

 Hoosic and Wachusett Mountains in Massachusetts, 

 and we trace it forming most of the hills and ridges 

 in the northern and western part of Connecticut. 



A large portion of the mountainous districts in 

 the State of New- York are formed of gneiss ; as 

 those of Essex, Montgomery, Herkimer, Oneida, 

 St. Lawrence, Orange, Dutchess, Putnam, and 

 Westchester counties. It forms the lofty High- 

 lands near West Point, as well as the high peaks of 

 Essex, one of which (Mount Marcy) rises 5467 feet 

 above the ocean. In many parts of this state, the 

 stratification of this rock is very obscure, and its 

 texture confusedly crystalline, the mica not tyeing 

 distinctly disposed in parallel layers. Indeed, it 

 may often be seen passing into distinct granite 



* See page 63 for a description of gneiss. 



