222 BULLETIN OF THE NEW YORK STATE MUSEUM 



abundance of good building stone in the next geological 

 member below it — the Corniferous limestone — whose out- 

 crop borders it on the north throughout the central and 

 western parts of the state, also prevents any use which 

 might be made of its stone. The single quarry in it is at 

 Chapinville, Ontario county. 



Hamilton Group 



The rocks of the Hamilton group crop out in a narrow 

 belt which runs from the Delaware river, in a north-east 

 course, across Sullivan and Ulster counties to the Hudson 

 valley near Kingston ; thence, north, in the foot-hills, bor- 

 dering the Catskills to Albany county ; then, bending to the 

 north-west, and west across the Helderberg mountains into 

 Schoharie county ; thence, increasing in width, through 

 Otsego, Madison and Onondaga counties, forming the upper 

 part of the Susquehanna and Chenango watersheds ; thence 

 west, across Cayuga, Seneca, Ontario, Livingston, Genesee 

 and Erie counties to Lake Erie. In this distance there is 

 some variation in composition and texture. In the western 

 and central parts of the state there is an immense develop- 

 ment of shales and the few quarries in the sandstones refer- 

 able to this group, are unimportant.*^' In the Helderbergs, 

 in the Hudson valley and thence, south-west, to the Dela- 

 ware river, the sandstones predominate and all of the beds 

 are more sandy than at the west. And there is a great de- 

 velopment of the bluish-gray, hard, compact, and even- 

 bedded sandstone, which is known as '' Hudson river blue- 

 stone," and is used so extensively as flagging. Some of the 

 thicker beds yield stone for building also. The sandstone 

 occurs interbedded irregularly with shales at most localities. 

 The blue-stone or flag-stone beds are generally in the upper 

 part of the Hamilton and they continue upwards in the 

 horizon of the Oneonta sandstone, which may be the equiv- 



* Geology of New York. Survey of the Fourth Geological District by James 

 Hall, Albany, 1843, pp. 184-5. 



