66 
GEOLOGY OF THE FOURTH DISTRICT. 
Localities. — The most easterly exposure of the rocks of this group within the district, is 
at the Wolcott ore bed, where some of the higher shale with fossils, as well as the iron ore, 
is found. Near Red-Creek village we find the green shale with fossils; at Wolcott furnace, 
the Pentamerus mass and the green shale above ; and at Whiting’s mill, three miles west of 
this place, the Pentamerus mass and lower green shale are seen. At Sodus point we find the 
iron ore and associated shales and limestone. At the former Shaker settlement on Little 
Sodus bay, all the members of the group, except the iron ores, are well exhibited, and this is 
one of the best localities in Wayne county for its examination. The Pentamerus mass forms 
a fall of twelve feet in the stream at that place ; the green shale, with fossils, appears below, 
in the bed.and banks of the creek ; and above the fall, the higher green shale with Grapto- 
lites, and the upper limestone with Atrypa, are both seen. 
In the eastern part of Williamson, a little north of the Ridge road, the green shale with 
Graptolites occurs, and a short distance to the north of this, the Pentamerus limestone. 
North of Sodus village the Pentamerus limestone and iron ore appear in several places. 
On Salmon creek, above the forge, the iron ore, green shale and Pentamerus limestone are 
all exposed, and still farther up the stream are found the thin calcareous layers with Atrypa 
hemispherica. Again at Ontario, just north of the Ridge road, the green shale with fossils 
may be seen; and finally, almost every stream north of the road from Wolcott to Rochester, 
exposes one or more members of the group. 
In Monroe county, the group appears near the head of Irondequoit bay, and again in the 
banks of the Genesee, which is its best exposure in the district. The canal is excavated in 
the same for some distance, about twelve miles from Rochester. In Sweden it is exposed on 
a small stream which crosses the canal a little west of Adams’ basin. There are also a few 
other localities, but the exposure is meagre. 
In Orleans county, some of its members are seen in the stream south of Albion ; also on 
the Oak-orchard creek, a mile south of Medina, the mass is well exposed, this being the best 
locality for order of superposition west of Rochester. 
In Niagara county, the limestone appears near the village of Middleport, where a small 
stream crosses it. A short distance west of Reynolds’ basin, the canal was excavated in the 
group, and the piles of fragments of the impure limestones, shaly matter, and hornstone, 
with numerous fossils, render this an attractive spot. Passing on to Lockport, we find the 
same rock exposed in the banks of the stream below the village, and, as before remarked, 
nearly the whole group is represented by the limestone. The limestone and the thin mass of 
lower green shale are seen in the escarpment at numerous points between Lockport and Lew¬ 
iston, where it crops out in the river bank. 
Thickness. —The thickness of the whole group in Wayne county, wherever it can be 
measured, is somewhat less than eighty feet; and in some places, from the thinning of the 
shale, it is little more than sixty feet. On the Genesee river, its different members appear as 
follows : 
