NIAGARA PERIOD. 
This is the first period that we will find in our study of 
the rocks of this county. As its name would lead us to 
suppose, it is over a part of the rocks of this period that 
the noted cataract of America makes its descent. The 
period is sub-divided into three groups: the Medina, the 
Clinton and the Niagara. 
The Medina Group with its two divisions, the Onripa 
CONGLOMERATE and the Mrepina SANDSIONE, is nowhere 
exposed in our county. It may, however, be easily studied 
in Oswego County, just north of us, where it occurs zz 
Satu, 
The Clinton Group is the first division of this period 
found in our county. It occurs in a narrow strip across 
our entire northern boundary. Although the group is 
about eighty feet in thickness, it is, nevertheless, difficult 
to find good exposures, since it is usually overlaid by sev- 
eral feet of soil and drift. 
By digging through the overlying soil near the shores 
of Oneida Lake, we come to a dark red shale, which forms. 
apart of this group. Broken fragments of the shale will" 
also be found scattered along both banks of Oneida River. 
There are also some soft, brittle, greenish-colored 
shales, constituting a part of this group, that are also 
found near Oneida Lake. These shales form the bed of 
the small creek emptying into the river near the outlet of 
the lake They also constitute the small knoll in the vil- 
lage of Brewerton on which the Disciples Church stands. 
The shales are well exposed in the excavation for a cellar 
just north of the church. On some of the small hillocks, 
where the overlying soil is thin, the upper surface of this 
shale is sometimes broken and worked up in ploughing. 
Several of our northern roads, also, cut through parts of 
this shale. The road running west from Brewerton has 
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