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[AiSEJlBLY 
it covers the green shale, including a thin mass of purple or choco- 
late colored shale. The green shale below the purple includes some 
wedge-shaped masses of crinoidal limestone, which have apparently 
taken this form in consequence of the insufficiency of the material to 
form a continuous stratum at the time of its deposition; the masses do 
not all hold the same place, appearing as if they had been infiltrated 
from above, some finding lower levels than others. 
Above the Pentamerus limestone we find again green shale, not much 
dissimilar to that below. This mass is twenty or thirty feet thick, and 
succeeded by a mass of encrinal limestone in thin layers, which is the 
constant associate of the upper green shale, and separates it from the 
Rochester shale. Associated with this encrinal limestone, is a bed of 
iron ore, the thickness of which we could not ascertain at this place 
without excavation, which was not made. This bed corresponds in po- 
sition with that at Wolcott furnace, and also with that in the eastern 
part of the town, from which ore is obtained for the supply of the Wol- 
cott furnace. 
The only indication of iron ore below the Pentamerus limestone, is 
the purple shale which has probably been colored by infiltration of iron 
from above. This shale occupies nearly the same position as the stra- 
tum of ore at Rochester, and the western part of Wayne county; this 
difference of position was probably produced while the whole mass was 
in a fluid state, by the iron passing through some of the strata, and 
forming beds upon others which were impermeable. With this view of 
its formation, it is not surprising that we should sometimes have one 
and sometimes two beds, and that their position in the rock should be 
variable, higher or lower in one place than another. 
Farther west we have evidence in favor of the hypothesis just advan- 
ced. At Cental's mill near Sodus bay, the ore occurs in several places, 
and particularly on the creek above the mill. The ore at this place is 
intermixed with the Pentamerus limestone, and replaces the lower 
strata of that rock. The green shale below is but two or three feet 
thick, the sandstone being visible at the same place. The purple shale 
noticed at the two last localities, is no where to be seen. Here then 
we find the ore to have changed its place, and to have formed a bed be- 
low the Pentamerus limestone. At the other localities, the purple shale 
may be considered as the representative of the iron ore stratum; while 
a sufficient quantity did not pass the superincumbent strata to form a 
bed of the ore, some of the finer, almost soluble, particles penetrated 
and colored the ro^k. But at Cental's mill and west of it, the whole 
