156 NEW YORK STATE MUSEUM 



The Onondaga-salt group is hardly seen in New York east of 

 Herkimer county. The succeeding formation, however, which is 

 grouped with the Salina is fairly persistent. 



Waterlime 

 Overlying the salt-bearing rocks and forming with them the On- 

 ondaga group is the Waterlime, a succession of dark-colored, fine- 

 grained and straight-bedded layers of limestone, attaining in Mad- 

 ison county a thickness of over 100 feet. It lies immediately over 

 the gray and drab limestones of the upper part of the salt group, 

 and is not divided from them by any very distinct or sudden 

 change in the appearance of the strata. The name is given from 

 the waterlime or hydraulic cement which is extensively manufac- 

 tured from two of the layers toward their upper part: these are 

 generally of a drab color, and separated from each other by a 

 thin mass of blue limestone. They are quarried, burnt and ground 

 on a very large scale near Manlius in Onondaga county, and the 

 hydraulic cement of Rosendale and Rondout is made from the 

 same beds. That manufactured at Williamsville, Erie county, 

 and at Buffalo, is from the upper limestones of the Salina group 

 below; and in Niagara and Orleans counties, a similar cement is 

 made from some layers of the Niagara group. 



HELDERBERG ROCKS 



Above the formations already described succeeds a thick series 

 of strata, chiefly limestone, separated by sandstone and grit rocks, 

 first described under the general name of the Helderberg rocks, 

 as they formed the great escarpment of the Helderberg moun- 

 tains in Albany county. From this place their edges may be 

 followed southward in the hills lying west of the Hudson river, 

 past the base of the Catskill mountains, and through Ulster county 

 as far as Kingston and Rondout; whence their outcrops bend 

 south westward and extend along the hills west of the valley of the 

 Delaware and Hudson canal, passing out of the state near the 

 northwest corner of New Jersey. They run still farther south- 

 westward, are seen above the Delaware Water Gap, and their 



