80 
GEOLOGY OF THE FOURTH DISTRICT 
22 , 
View of Niagara Falls from the Canada shore. From a drawing by Mrs. Hall. 
11. NIAGARA GROUP. 
Geodiferous limerock, and Calciferous slate, of Eaton. Lockport limestone , and Rochester 
shale, of the Annual Reports of the Fourth District. Upper part of the Protean group, 
of the Annual Reports of the Third District. 
(A Part of No. 6, if recognized, in the Pennsylvania Survey.) 
[See Section of Niagara River from Lewiston to the Falls, Plate 3; and L. 1. of woodcut, p. 27.] 
This group consists of two distinct members, a shale and limestone, which, possessing 
many features in common, are recognized as the products of one period; during which, how¬ 
ever, there was an important change in the lithological products, and a less one in the organic 
forms. The shale continues a very uniform deposit throughout the whole extent of the dis¬ 
trict ; while the limestone, from a thin, dark-colored concretionary mass, becomes an extensive 
and conspicuous rock, constantly increasing in thickness in a westerly direction, even far 
beyond the limits of the State. 
The Cataract of Niagara is produced by the passage of the river over this limestone and 
shale ; and from being a well known and extremely interesting point, as well as exhibiting the 
greatest natural development of these rocks within the limits of the State, this name is adopted 
for its designation. 
