176 HELDERBERG DIVISION. 



known that all the limestones in the New-York system contain it : even the Stockbiiilge 

 limestone, in the Taconic system, contains occasionally a few layers of light colored horn- 

 stone. 



Relations of the Onondaga limestone. At Leeds and New-Scotland, it reposes on the 

 Schoharie grit ; at Cherry valley, upon the Oriskany sandstone ; at Manlius, upon the 

 concretionary part of the pentamerus ; at Tyler Post-office, or rather a mile west, at Split- 

 rock, upon the Manlius waterlimes, in which connection it continues to Blackrock. Above, 

 from east to west, so far as New-York is concerned, it is every where succeeded by the 

 Marcellus shales, a black shaly or rather slaty rock. At some other points farther west, 

 however, there are vestiges of the Oriskany sandstone, and in a few places it lias its usual 

 thickness. For instance, five miles east of Cayuga bridge, as well as at Auburn, the 

 latter rock is present : in a few localities, it is represented by a sprinkling of sand ; at 

 others, as at Splitrock, by a few boulders and cobblestones, which are mostly derived from 

 the Niagara limestone, and some of which may possibly weigh fifty pounds. This may 

 be regarded as an important fact. At the east, the Onondaga limestone is separated by 

 several distinct and well characterized deposits from tlie Niagara limestone ; but at the 

 west, they are separated only by the red and green shales, and as these seem to be inter- 

 calated or rather local deposits, it is possible the two limestones may be actually in contact 

 still farther west or southwest. 



JVatural joints and fissures. The Onondaga limestone is traversed with some show of 

 regularity by joints, which, upon the surface, become wide fissures : these admit the 

 passage of water ; and, hence, wherever it is the surface rock, the rain subsides and passes 

 through it, or to that stratum, whatever it may be, which is impervious, when it is thrown 

 out. Owing to this stratum, no springs are found except at its base, and there frequently 

 large ones issue at once of sufficient size to turn a mill-wheel. At Clark's in New-Scot- 

 land in Albany county, at Springport in Cayuga county, and at Clarence in Erie county, 

 are springs of this description. In many instances, however, they are to be regarded only 

 as subterranean streams, wliich have entered one fissure at a distance, and at last found 

 their way out through another. The disappearance of Allen's creek at Leroy, which is 

 noticed by Mr. Hall, is an example. This is not indeed an uncommon occurrence at the 

 south and southwest, in the region of the Carboniferous limestone. The waters are cold, 

 but are not sufficiently charged with inorganic matter to be entitled to the appellation of 

 mineral waters : they are as pure as most springs in a limestone district, and they are quite 

 unlike those waters which have percolated through the strata composing the Onondaga-salt 

 group. 



Jigricultural characters. It has been generally supposed that this limestone exerted an 

 important influence upon the agricultural productions of the central and western counties 

 of New-York ; indeed, that this rock furnishes one of the essential elements of a wheat 

 soil, and was also principally instrumental in giving this character to quite a wide belt of 

 country to the south, or beyond its visible limit. That it does exert an important influence 



