350 The Parallel Drift-Hills of Wefitern New York. 



Above the Medina sandstone rises the Clinton gronp, and 

 upon this rests the Niagara, with no well-marked line dividing 

 them. The Clinton is composed of thin-bedded limestones, 

 shales, sandstones, and, in some places, thin beds of argillaceous 

 iron ore. Owing to its lithological character, it has not exerted 

 a very powerful influence upon the present topographical fea- 

 tures of the region. Not so, however, is it with the over- 

 lying Niagara. The lower member of this group, here as 

 further west, comprises thin-bedded, impure limestones and 

 about eighty feet of shale ; while the upper member is a mass of 

 heavy-bedded, compact limestone. The geological position of 

 this limestone, dividing as it does the great mass of soft rocks 

 beneath from the still softer Salina shales above, has made it an 

 important agent in the production of the present topography of 

 the region. Economically, it is of importance to the inhabit- 

 ants as the source from which they obtain lime. 



There are no data for determining the exact width of the tract 

 of which the Niagara is the surface rock, since its junction with 

 the next succeeding group is nowhere apparent ; it is, however, 

 probably from tAvo to five miles wide. 



Along Wolcott Creek, the best nearly continuous exposure (f 

 the Clinton and Niagara, both together occupy the surface for 

 five or six miles. Like the Medina on which they rest, they 

 rise both east and west. 



Upon the Niagara rests the Salina group, forming the surface 

 rock all the way to Cayuga and Seneca lakes. The shales of 

 this group are exposed in numerous places, especially along the 

 valley of the Clyde and Seneca rivers, in railway cuttings, and 

 in excavations for the Erie Canal. In two localities in this val- 

 ley, namely, in a railway-cutting two miles west of Savannah, 

 and in a hillside three or four miles southeast of Lyons, I have 

 observed the upper, water-lime, layers of this group, in place. 



With the Salina group, ends the succession of surface rocks of 

 the region occupied by the parallel drift-hills. Above and to 

 the south are, however, rocks which have exerted a marked 

 causative influence upon the topography, not only of this region, 

 but of that of the whole Ontario basin. 



Passing the Water-lime and Oriskany sandstone,'-with the mere 

 mention of their names, for they are of little importance here, 



