42 
GEOLOGY OF THE FOURTH DISTRICT. 
only in this rock ; the structure is quite unlike the bodies of this kind usually met with, and 
seems due to the decomposition of iron pyrites, or some other substance where the force was 
directed outwards, rather than toward the centre. 
The sandy portions of the Third division often contain oblong or rounded accretions or peb¬ 
bles of shale, which on weathering are dissolved out, and leave corresponding cavities. These 
appear much like worn fragments of the red shaly part of the rock, and are distinctly lami¬ 
nated ; still from the manner of their being imbedded, and uniform size, they are probably 
referable to the first named cause. They are always of a deep reddish brown, while the mass 
which contains them is frequently much lighter in color. This, if they were contemporaneous, 
only shows the superior attraction of the argillaceous mud, for the coloring matter, over the 
sandy portions of the rock. The flattened oblong form of many, renders it a matter of doubt 
whether they are accretions or pebbles. 
Localities. — This rock appears as a conglomerate in a ravine near the level of the lake, 
about two miles northeast of Wolcott furnace. This was the farthest eastern point at which 
it could be detected in the district. An examination was made for this rock from the Wolcott 
ore bed towards the lake, but without success, the low marshy ground preventing its appear¬ 
ance. The same is true at Wolcott furnace, and also on the west side of Little Sodus bay. 
The sandstone is quarried on Beard’s creek and Little Red creek in the town of Wolcott, 
and used in the construction of furnaces. It is again well exposed near the forge on Salmon 
creek, and contains its characteristic fossil, the Fucoides Harlani. It also appears in the 
town of Williamson, near the lake shore. 
In Monroe county, in the town of Penfield, this sandstone appears on the lake shore, pre¬ 
senting a few feet of the strata below the clay and gravel. On the eastern side of Irondequoit 
bay, it has been quarried for the piers at the mouth of the Genesee. It appears again near 
the head of the bay. 
The lower falls of the Genesee are caused by this rock, more than one hundred feet being 
exposed at that place. From the falls it forms both banks of the river, extending nearly to 
the lake. This is one of the best localities in the district. It is again seen a little north of 
Adams’s basin, about twelve miles west of Rochester. In passing through Sweden, about 
twenty miles west of Rochester, the bed of the canal was excavated in this rock. 
West of the Genesee the sandstone does not appear on the lake shore in Monroe county, 
but by tracing up the small streams it may always be found; it is of little interest, however, 
from its uniform character and the absence of fossils. A short distance northwest of Adams’s 
basin, the rock with Fucoides Harlani appears in the bed of a small stream. In the neighbor¬ 
hood of Clarkson corners, it approaches the surface, giving its characteristic color to the soil. 
The upper part of the mass, abounding in the Fucoides Harlani, is quarried near the village 
of Brockport; and also in the northern part of Clarendon, Orleans county, forming a good and 
durable building and flagging stone. The softer portions are well developed in the banks of 
Sandy creek, particularly at the crossing of the Ridge road, and also nearer to the lake. 
