152 NEW YORK STATE MD8EUM 



upon the Hudson river schists. This is probably equivalent to 

 the Oneida conglomerate, or possibly the base of the Medina 

 group. 



The source from which such enormous quantities of rolled 

 pebbles of quartz could have been derived and the mode by 

 which they could have been spread >so widely over a sea bottom 

 is a very obscure question in geology. Several other such forma- 

 tions of conglomerate are known, two of which occur at the 

 lower and middle parts of the Carboniferous system. 



Medina Sandstone 



The next succeeding group is that named from a village in Or- 

 leans county where it is well exposed. 



It is a huge mass of sandy and shaly rock, of very variable 

 hardness from soft marl to hard sandstone, and varying in color 

 from deep red to olive and light gray. It is not known in the far 

 west, seeming to thin out and disappear before reaching Wiscon- 

 sin, but is well seen on the Niagara river, where it forms most of 

 the precipice near Lewiston. At this point the lower part is a 

 soft red shale, with harder and lighter colored layers above, to 

 one heavy bed of which the cables of the Lewiston suspension 

 bridge are fastened. This sandstone may also be seen in the 

 lower part of the river cliffs, extending as far as the upper 

 Suspension Bridge. The same rock is quarried near the lower 

 part of Lockport for building and flagstone, and it forms the lower 

 falls of the Genesee at Rochester, at the top of which the hard 

 uppermost layer, called the ' Gray band/ is very conspicuous from 

 its light color. Further east, the same rock forms the falls of the 

 Oswego river at Fulton; but in the Mohawk valley it thins out, 

 and disappears. In southeastern New York, however, near Ron- 

 dout, it re-appears and is very thick at the Delaware water gap 

 in New Jersey and Pennsylvania, reaching, in the latter state, 

 the thickness of 1,000 feet; and it may be recognized as far south 

 as Alabama. 



