REPORT OF EXECUTIVE COMMITTEE. 
25 
New York as the Onondaga Salt Group, has been found 
hitherto in but one locality, to wit: in the vicinity of Milwau¬ 
kee, where it has an exposure of a few miles in breadth on 
the lake between that city and the town of Pierceville. It is 
a compact, ash-gray, magnesian limestone, thin-bedded and 
laminated with thin layers of dark, glazed, shaly matter be¬ 
tween. It is the Onondaga Salt Group which includes the 
beds of Gypsum, so abundant in New York and Canada West; 
but that mineral does not seem to be a part of the group in 
this State. 
We have now completed a cursory review of the general 
geology of the State, which, together with the map, will 
enable the intelligent reader, however little acquainted with the 
general principles and the technicalities of the science, to 
acquire a fair knowledge of the character, order and mode of 
occurrence of the principal rock formations. 
MINERAL DEPOSITS. 
These are both numerous and valuable, constituting an im¬ 
portant share of the natural wealth of the State. 
The “ Lead Region” occupies an area equivalent to that 
embraced within the Wisconsin river on the north, the Rock 
river on the east, the State line of Illinois on the south and 
the Mississippi on the west, or about 2,200 square miles. It 
nowhere, except in the case of a few mounds, rises to an eleva¬ 
tion of more than about 500 feet, and is characterized by a ridge 
or “water shed” running parallel with the Wisconsin and 
about 12 or 15 miles from the general course of that stream. 
It is this shed from which the streams that drain the district 
take their origin, flowing north and south. 
A striking peculiarity of the geology of this region—-which 
may have been intimated in previous remarks — consists in the 
entire denudation from the surface, not only of the drift which 
covers the eastern and northern portions of the State but 
likewise of all the recent rock formations which lie above the 
Trenton Limestone. What the mighty agencies were that 
accomplished this vast work of clearing off the mines for the 
