CORNIFEROUS LIMESTONE. 
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22. CORNIFEROUS LIMESTONE. 
Upper part of the Corniferous Limerock of Eaton. Seneca Limestone of the Annual 
Reports. 
This rock is one of the most persistent of any in the series, and at the same time maintains 
a uniformity in lithological character, and in the occurrence of certain fossils, scarcely possessed 
by any other. It is known to extend from the Helderberg mountains on the Hudson river, 
to the Niagara river, and thence far into Canada. This rock forms the terminating mass of 
the second limestone terrace to the south of lake Ontario, and with the Onondaga limestone 
and the upper part of the Salt group forms the whole height of the same in the Fourth Dis¬ 
trict. It follows the sarne line of direction as noticed in the last described rock, and every 
where succeeds that mass, being always thicker and more prominent. By reference to the 
Geological Map, the limits of this and the next lower rock will be seen, occupying in the 
Fourth District a width of from two to four or five miles, dipping gradually to the south, and 
disappearing beneath the Marcellus Shale. 
It has suffered a great amount of denudation at several points, as noticed under the pre¬ 
ceding rock, the two being almost always in the same line of outcrop. 
This rock has a prominent and well defined outline upon the north, and gives rise to a 
prominent feature in the topography of the country as well as to many interesting points in 
the scenery. All the smaller streams passing over it present rapids or cascades of more or 
less interest. The larger streams, and the lakes of Cayuga and Seneca which extend north 
beyond this rock, have excavated their channels deeply into it giving no evidence of its exis¬ 
tence in their beds. It forms a slight barrier however at the outlet of lake Erie at Black 
Rock, producing a rapid current with considerable descent, and presenting a small island 
just above the water which is all that now remains to show that the rock was once continuous 
from the two shores. 
[Geol. 4th Dist.] 
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