388 * NEW YORK STATE MUSEUM 



Sullivan and Ulster counties to the Hudson valley near Kingston ; 

 thence north, in the foot-hills, bordering the Catskills, to 

 Albany county ; then, bending to the northwest and west across 

 the Helderberg mountains into Schoharie county ; thence, increas- 

 ing in width, through Otsego, Madison and Onondaga counties, 

 forming the upper part of the Susquehanna and Chenango water- 

 sheds; thence west, across Cayuga, Seneca, Ontario, Livingston, 

 G-enesee 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 development 

 of shales and the few quarries in the sandstones referable to this 

 group are unimportant.* In the Helderbergs, in the Hudson val- 

 ley and thence, southwest, to the Delaware river, the sand- 

 stones predominate, and all of the beds are more sandy 

 than at the west. There is a great development of the 

 bluish-gray, hard, compact and even-bedded sandstone, which 

 is known as " Hudson river bluestone," and is used so extensively 

 as flagging. Some of the thicker beds yield stone for build- 

 ing also. The sandstone occurs interbedded irregularly with 

 shales at most localities. The bluestone or flagstone beds 

 are generally in the upper part of the Hamilton and they 

 continue upward into the horizon of the Oneonta sandstone- 

 The number of quarries in this blue stone district, in Sullivan. 

 Ulster, Greene, Albany and Schoharie counties, is large and can 

 be increased indefinitely, as nearly the whole area of the forma- 

 tion appears to be capable of producing stone for flagging or for 

 building. The difficulty of indicating the division line between 

 the Hamilton and the Oneonta and the Hamilton and the Portage 

 group of rocks makes it impossible to refer to localities more par- 

 ticularly. The quarries near Cooperstown, in the lake region, 

 particularly at Atwater, Trumansburg, Watkins' Glen and 

 Penn Yan belong to the Hamilton group. 



Portage Group. 



In this is included the Oneonta sandstone, the limits of which 

 at the east can not be indicated and the flagstone beds of the 

 Hudson valley and of the eastern part of the State continue up 



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

 1843, pp. 184-5. 



