REPORT OF EXECUTIVE COMMITTEE. 
23 
and thence running due south, on the east, the State line on 
the south, and the Mississippi on the south-west. 
The Buff formation includes what are sometimes called the 
Black-river and Birds-eye limestones. In the south-western 
part of this State, it rests directly upon the Upper Sandstone. 
It consists of an impure, huff-colored magnesian carbonate of 
lime, and is frequently less than twenty feet in thickness; in 
other localities its lower beds are rather argillaceous than oth¬ 
erwise, This rock also makes its appearance at different places 
along the Mississippi above La Crosse, often capping cliffs 
and monumental outliers in the north-western portion of this 
State; while, in Minnesota it becomes a continuous formation, 
being conspicuous at St. Anthony Falls and several points 
near the line of boundary. 
The Blue Limestone is the Trenton proper. It is a thin- 
bedded, bluish or bluish-grey magnesian rock. Where it occurs 
in the more eastern part of the State along Lake Winnebago 
and the Fox river, it is compact, firm, evenly-bedded, and is 
quite valuable for economical uses. The quarries at Apple- 
ton, Menasha, Oshkosh, Ripon, Waupun, Janesville, Mineral 
Point, Sun Prairie, &c., are of this rock. 
The Galena formation of the Trenton Group overlies the 
preceding, as before intimated, and is the lead-bearing lime¬ 
stone. It is of a light or yellowish-grey color, is heavy-bedded, 
compact, and consists of minute crystals of magnesian carbo¬ 
nate ; characterized to some extent, especially in some locali¬ 
ties, by small cavities, lined with calcareous spar, iron pyrites 
and sometimes galena. It weathers very irregularly, and is 
not much used as a building stone. A portion of the quarry 
at Waupun, however, is of this rock. 
Succeeding the Trenton Group, and lying directly upon it, 
we have a series of 
Blue and Green Shales , for sometime called by geologists 
Hudson River Shale. It has its out-crop along the east shores 
of Green Bay, Lake Winnebago, Lake Iloricon and thence 
south to the boundary line of the State. It also shows itself 
at several isolated spots and is present in all the mounds. Its 
