ONTARIO DIVISION. 141 



6. The lower limestones of this series give origin to the celebrated springs of Saratoga 



county, where they issue from a fault. Tlie shales of the Hudson river give origin 

 to many weak hepatic springs, or those whose waters are cliarged with sul])huretted 

 hydrogen. The sandstones give origin to waters comparatively pure. Faults and 

 fractures, and undulations of the strata, are not unconunon. Of the latter kind of 

 displacements, the Mohawk valley furnishes several good examples : thus, at or 

 near Fultonville, the Utica slate at one time appears in the banks at the level of 

 the canal ; at the same level, and farther on, the trenton and even the birdscye 

 are brought up so as to occupy the same plane as the the Utica slate. This fact 

 should not be lost sight of, in estimating the thickness of rocks by the amount of 

 dip, when they are concealed beneath the soil. 



7. The rocks which are useful for construction, are the Potsdam sandstone, Calciforous 



sandstone, and the gray sandstone of Oneida and Oswego counties. The Isle La- 

 motte limestone, which is the same as that at Glensfalls, furnishes a fine black 

 marble. 



8. The peculiarities in the characters of the organic remains, are, that the species are not 



numerous, but the individuals are, and they occupy extremely limited ranges both 

 vertically and horizontallj^ : some in fact occupy but a few strata of only two or 

 three feet in thickness. 



9. This series, when considered in its totality, is well entitled to the appellation of a 



system : its thickness and its fossils both support and sustain this view. This view, 

 however, is founded upon a comparison of this series with others which constitute 

 divisions of a similar kind in this country and in Europe, as the Devonian, Old Red, 

 Permian, &c. 



II. ONTARIO DIVISION. 



Geographically this division of the New- York rocks is very clearly defined. It appears 

 in characteristic masses only on the south of Lake Ontario. It embraces, however, rocks 

 which are somewhat diverse in character, and hence it will be necessary to consider them 

 under separate and distinct parts or subdivisions. The individual members are given on 

 page 115, with the subordinate divisions proposed, and which in the ascending order stand 

 thus : 



1. Medina sandstone, 



2. Green shales, grits and limestones, composing the Clinton group. 



3. Gypseous rocks, or the Onondaga-salt group, with the red shale reposing upon the Niagara limestone. 



