CLINTON GROUP. 
67 
Feet. Inches. 
5. Upper limestone. 18 4. 
4. Upper green shale,. 24 00 
3. Pentamerus limestone. 14 00 
2. Iron ore bed,. 0 14 
1. Lower green shale,. 23 00 
80 G 
At Lockport the calcareous portion is about twenty feet thick, and the shale scarcely defi¬ 
nable, apparently mingled with the terminal part of the Medina sandstone. On the Niagara 
river the limestone is twenty-five feet thick, and the shale below four feet. 
Mineral Contents of the Group. 
The first mineral which meets the eye is the hornstone of the Pentamerus mass ; this often 
passes into translucent varieties, and forms little cavities lined with calcedony. Fossils which 
are enclosed in the mass, frequently, on breaking, present a cavity lined with delicate quartz 
crystals, or calcedony. At Rochester large geodes have been found lined with this mineral, 
in mammillary or botryoidal forms, producing beautiful specimens. Siliceous sinter and 
cacholong both occur in the same association, and Prof. Dewey mentions carnelian as occur¬ 
ring here. 
The sulphates of baryta, and of lime, are both found in the rocks of this group, and in several 
localities. The sulphate of baryta occurs in spheroidal cavities in the Pentamerus mass, and 
more rarely in the upper limestone. Groups of crystals, and cavities lined with the same, of 
a beautiful flesh-red color, occur in the oolitic iron ore at Wolcott, and more rarely with 
the ore in other places. Crystallized carbonate of lime is found with the sulphate of baryta, 
and in other situations. The sulphate of lime is principally confined to the upper limestone, 
where it often forms masses of considerable size, partially filling cavities which have appa¬ 
rently resulted from the decomposition of iron pyrites. Pyritous copper and green carbonate 
of copper occur in the Pentamerus mass, and Prof. Dewey has discovered some spiculas of 
native copper in the same rock. I have detected the green carbonate of copper in cavities in 
the calcedony or sinter, at Medina and near Reynolds’ basin. 
Mud Casts. — The lower strata of the Pentamerus mass, on the Genesee, are of a shaly 
sandstone ; these, when in contact with the shale below, often present surfaces curiously con¬ 
torted and twisted. They appear as if they had been in a semi-fluid state, and forced along 
over the yielding mud, previously rendered uneven by the flowing of water over the surface, by 
which little depressions had been scooped out at short intervals, and into these the subsequent 
mass was deposited. 
Another appearance attending these lower strata, is the occurrence upon their under side 
of long straight, or slightly tortuous ridges, standing out in bold relief upon the slab. These 
I have denominated casts of mud-furrows, and suppose them to have been made in depressions 
