GEOLOGY OF THE FOURTH DISTRICT. 
62 
all of the upper bed.* At the Shaker village, Sodus point, the position of the upper bed was 
not distinctly visible, though all the deposits below were so. Upon excavating the earth, 
large masses of ore were obtained ; and though from the quantity of fragments of the superior 
rock, I did not find the ore actually in place, there is still scarcely a doubt of its existence at 
that spot. Its place is in the bed and banks of the stream a few rods above the mill-dam. 
The place of the lower bed is here distinctly seen, but the ore is absent, its only represen¬ 
tative being the small quantity of carbonate of iron disseminated in the limestone above. 
I have not been able to discover the upper bed west of this place ; the next locality exhibits 
a thinning of the lower green shale, with the ore intermixed with the Pentamerus limestone. 
North of Sodus village, and in the town of Ontario, the ore is evidently from the lower bed, 
the Pentamerus limestone always appearing above. The last place westward where the ore 
is seen as already mentioned, is the lower bed, on the Genesee. 
3. Pentamerus Limestone of Clinton Group. f 
This mass, in some places, is composed almost entirely of thin beds of impure limestone, 
which alternate with thin layers or laminae of green shale; in other places it is a nearly pure 
crystalline limestone, composed of broken valves of Pentamera and other shells, with a large 
proportion of crinoidal joints. The latter character prevails in some places in the eastern part 
of Wayne county, and is seen distinctly at Whiting’s mill, three miles west of Wolcott fur¬ 
nace. To this structure, producing unequal expansion of the crystalline and uncrystalline por¬ 
tions, is due its power of withstanding heat, which has brought it into use as an ordinary fire¬ 
stone for chimneys, hearths, and some of the less exposed parts of furnaces. 
At Sodus point, and a mile northeast of Wolcott furnace, the shells of Pentamerus are 
imbedded in a shaly mass, with just sufficient calcareous matter to make it firmly cohere. 
North of Sodus village the mass is free from argillaceous matter. 
On the Genesee river this rock outcrops in the banks on either side, and stretches across 
the stream, forming the middle falls. In this situation we find less shale, but an intermixture 
of shaly and calcareous sandstone, which in some places predominates. Much of the mass 
is a crystalline siliceous limestone, very compact and tough, forming excellent building mate¬ 
rials, but difficult, from its hardness, to work. The predominating siliceous character at this 
locality, induced Prof. Eaton to give it the name of Ferriferous sandrock; this term cannot 
be retained, from the fact that in nearly all localities examined it is comparatively free from 
sand, and its distinctive feature is calcareous. 
In numerous localities in Monroe county it appears as a limestone, and is quarried in many 
places for the same uses as in Wayne county. The Pentamerus, on the Genesee, is confined 
* In some places, from the proximity of the Lake level, it is impossible to ascertain without boring, whether the lower stratum 
of ore does exist or not. 
f This term is used in this manner to avoid confusion, the term Pentamerus limestone being used to designate that mass 
charged with Pentamerus gakatus in the Helderberg series. 
