376 
HELDERBERG DIVISION. 
known that all the limestones in the New-York system contain it: even the Stockbridge 
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 has 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 the 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. 
JYatural 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, which 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. 
Agricultural 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 
