GEOLOGIC FORMATIONS OF NEW TORE 149 



It attains an entire thickness of more than 300 feet, and, suc- 

 ceeding the lower rocks as already described, its edges surround 

 the great Adirondack region in an almost unbroken circuit. Seen 

 at Glens Falls on the Hudson, along the Mohawk at Fort Plain 

 and elsewhere, on the west shore of Lake Champlain, and at 

 many points on the shores of the St Lawrence, it also outcrops 

 along the valley of the Black river and is crossed by West Canada 

 creek at Trenton Falls, from which place it takes its name. 



In many places it furnishes building stone of excellent quality. 



Hudson River Group 



This formation, which is next in upward succession, is an enor- 

 mous deposit of sandstone, slate and shale. The lower part of 

 the Hudson river group is a fissile black slate about 75 feet thick, 

 known as the Utica slate. 



The higher strata, to which the name of the Hudson river 

 group is more usually restricted, are gray slaty masses, with 

 coarse sandstones, especially toward the top, and in some places 

 near the summit of the group, a coarse sparry limestone. 



In the eastern part of the state these rocks are 3,500 feet thick, 

 as shown by a boring near Altamont in Albany county. They 

 are well seen in the north of Oswego county, near Pulaski, the 

 south of Lewis county and the middle of Oneida county; also 

 through the Mohawk valley, and from Glens Falls southward 

 along the Hudson river, from which these strata take their name. 

 West of Schenectady they are generally level and undisturbed; 

 but near the Hudson river these strata are upheaved, broken, 

 folded and faulted in every conceivable manner, as may well be 

 seen in many places near Cohoes and Albany and along the Hud- 

 son river railroad. In much of this disturbed region the rock 

 has been changed in texture by the forces to which it has been 

 subjected and fossils are very rare. 



That part of New York lying east of the Hudson, and along 

 the western border of New England is formed of an enormous 

 mass of upheaved and contorted strata of slate, schist sandstone 

 and limestone, which were at one time supposed to be older than 



