BREACHES IN THE INNER 



deposites are found contiguous to another formation of 

 shistons trap and fetid limestone, full of marine shells and 

 madrepores. 



4. The breach at the upper falls of the Mohawk. 



I have several times visited this remarkable spot, and 

 am convinced the rocks formed at some remote period a 

 mound which opposed the progress of the water eastward. 

 " As you approach the falls," says Governor Clinton, 

 " the river becomes narrow and deep, and you pass 

 through immense rocks, principally of granite, inter- 

 spersed with limestone. In various places you observe 

 profound excavations in the rocks, made by the agitation 

 of pebbles in the fissures, and in some places the river is 

 not more than twenty yards wide. As you approach the 

 western extremity of the hills, you find them about half 

 a mile distant from summit to summit, and at least three 

 hundred feet high. The rocks are composed of granite, 

 and many of them are thirty or forty feet thick ; and the 

 whole mountain extends at least half a mile from east to 

 west. You see them piled on each other like Ossa on 

 Pelion; and in other places huge fragments scattered 

 about, indicating evidently a violent rupture of the wa- 

 ters through this place, as if they had been formerly 

 dammed up and forced a passage; and in all directions 

 you behold great rocks exhibiting rotundities, points 

 and cavities, as if worn by the violence of the waves or 

 hurled from their ancient positions."* 



As is the consequence in such cases, the upper country 

 wears the face of a drained tract, and the lower country 



* Introductory Discourse before the New-York Literary and Philo- 

 sophical Society, note Q, 



