REPORT OF EXECUTIVE COMMITTEE. 
19 
dining continuation of the Porcupine Mountains of North¬ 
western Michigan—the highest summits of which are about 
twelve hundred feet above Lake Superior, or eighteen hundred 
feet above the ocean level. This hight is attained at a distance 
of only a few miles from the shore of the lake, giving the 
streams which flow northward a very rapid descent. On the 
southern side, however, the general descent is gradual, with a 
secondary slope, eastward and westward, down which flow tho 
principal rivers of the State, emptying into the lake and the 
Mississippi. The elevation of that portion which constitutes 
Southern Wisconsin, is only about two hundred feet above the 
level of Lake Michigan. Making no allowance for inequalities 
of surface, the face of the State, therefore, presents the form 
of a huge tortoise shell, elevated at the northern extremity, so 
as to slope southward—the great northern and southern axis or 
dividing ridge coinciding in direction very nearly with the 
Fourth Principal Meridian. 
The principal rivers are the Wisconsin, the Chippewa and 
the Wolf (improperly called Fox). There are also many other 
rivers of considerable magnitude — some of them, as the Rock, 
navigable for small boats in time of high water. All the larger 
streams have their origin in the elevated plateau above referred 
to as occupying the northern and central portions of the State, 
and which is marked on the accompanying map as “ The region 
of Lakes and Marshes.” Many of the streams are precipita¬ 
ted over rocky descents and occasional precipices, forming most 
beautiful rapids and cascades. 
Resides the great inland border seas, Superior and Michigan, 
the largest in the world, Wisconsin abounds in lakes of smaller 
size, profusely scattered over the entire surface. They vary in 
extent from one to thirty miles, and are excelled by none in 
the world for the purity of their waters, or the beauty and pic¬ 
turesqueness of their surroundings. 
GENERAL GEOLOGY. 
Azoic, or Primitive Pocks .—With the exception of a strip 
or narrow belt of the Lower Sandstone along the shore of Lake 
