NIAGARA GROUP. 
83 
sometimes of equal thickness to the limestone, though generally thinner. The shale sepa¬ 
rating the lower courses is green like that below; but higher, it becomes of the same color 
and character as that above. The interlaminated shale is in all cases destitute of fossils. 
The shale is partially exposed in several small streams, and in the low escarpment which 
extends westward from Rochester. In the town of Sweden, that escarpment has become 
higher, and the shale is in some places well exhibited. One of the best localities is at Mar¬ 
shall’s saw-mill, in the town before mentioned, where the small stream (a branch of Salmon 
creek) has excavated its channel in this rock. The banks scarcely differ in color and ap¬ 
pearance from the soil around, and it is only from fossils that the mass is distinguished from 
ordinary clay. At one point where there has been a fresh exposure, the rock appears in all 
its characters, and contains abundance of fossils. 
Passing westward from Monroe county, the escarpment constantly rises, and the shale 
appears in all the ravines and water-courses; and the smallest gorge is often sufficient to 
afford a good exposure of the rock, which is every where charged with fossils. Even in the 
banks of ditches, passing through some level grounds, I have obtained many fine specimens 
from the decomposed portions. 
Below Farwell’s mills in the town of Clarendon, and again on the south side of Jefferson 
lake, and along the escarpment between this and Albion, the shale is exposed in many places, 
and in all yields abundance of its organic remains, which appear to increase in number to¬ 
wards the west. 
At Shelby falls, the upper part of the shale, and the siliceous limestone terminating it, both 
appear; and the former continues in view for a mile north of this point, in the banks of the 
stream. Thence to Lockport, the rock may be every where examined along the northern 
slope of the Great Terrace, except in places where there has been too great an accumulation 
of drift. 
At Lockport, both from natural exposure, and from artificial excavations in the construction 
and enlargement of the Erie canal, this rock in all its varieties is better exhibited than else¬ 
where west of the Genesee. The banks of the natural gorge where the canal enters the 
escarpment, appear like immense beds of clay surmounted by limestone. The effect of de¬ 
composition has been such as to obscure the natural color and appearance of the mass. Along 
the sloping sides of these apparent clay banks we find vast numbers of the peculiar fossils of 
the rock, and every excavation adds a fresh supply to the almost exhaustless numbers. The 
shells, being purely calcareous, resist the effects of decomposition; while the mass around 
crumbles down, leaving them in a perfect condition, and entirely separate from the matrix. 
Between Lockport and the Niagara river, the shale appears in numerous ravines and gorges 
which indent the edge of the great escarpment. The whole thickness of the shale is exposed 
in both banks of the Niagara, extending from Lewiston and Queenston to the Falls. From 
difficulty of access, however, it does not afford so good an opportunity of investigation as at 
Lockport and Rochester. At the points where I have been able to examine it, it retains the 
same characters and affords the same fossils as at localities farther east. Along a part of the 
distance, it is partially obscured by fallen fragments of the limestone which caps the cliff. 
