380 GEOLOGY OF OHIO. 
site of the dam, but it is now hid by deep water. At the dam, and in 
the recent excavation for the enlargement of the mill-race, half a mile 
below, this stone is opened, and found to produce even-grained blocks 
and pieces of irregular shape, but which with care could be obtained of 
~ almost any desired dimensions. It is seen in the bed of the river for 
the distance of half a mile below the dam. It is not easily separable 
from No. 2, into which it graduates. 
The fossils found in No. 2 are in a very fragmentary condition. There 
are numerous pieces of crinoidal stems, and traces of a bivalve, appar- 
ently a Spirifer. A fractured trilobite was also seen. .The workmen re- 
port finding “turtles’-backs” as large as a man’s hand, which may be 
Macropetalichthys. 
The junction of No. 2 with No. 3 is jagged with lignilitic prominences,. 
or suture-shaped roughness. The lignilitic crystals are often two inches 
long, and covered with black films, while in the depressions an arena- 
ceous limestone is deposited. Sometimes in quarrying, these suture- 
joints are so firm as to tear up the first layer of No. 3 rather than sepa- 
rate. . 
No 3swells gently upward, bringing itself into contact with the cur- 
rent of the river for a distance of half a mile below the “Purdy Mills.” 
It first shows a dip west, but changes to east, so as to permit the return 
of the sandstone (No. 1) at the mouth of the Beaver Creek, a mile below 
the village of Grand Rapids. 
About four miles still further down the river, opposite the village of 
Otsego, the Oriskany is again intersected by the Maumee. It is seen 
here in beds of eight to twenty-eight inches. The grains are fine and 
_ white, although there are some places which show an apparent quartz- 
itic structure, the silica grains being apparently crystallized into a solid 
mass, losing their forms, while some of it 1s more properly an arenaceous, 
magnesian limestone. Within, this stone is of a lght-blue color, or 
gray, with spots of blue. The blue sometimes prevails near the junction 
of the beds; indeed, the bedding-planes are very often separated. by a 
very blue or purple lamination, which is also sandy. These laminations, 
which are sometimes an inch thick, are so split not infrequently as to 
include lenticular patches of lighter rock like the mass of the thicker 
beds. The whole weathers a buff or almost white. The following sec- 
tion was taken at this place, in descending order: 
No. 1. Limestone; close-grained; crystalline, light drab, or dark 
drab, and porous; in one bed. The dark and porous 
parts have the forms of inverted kettles, and show traces 
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