454 DESCRIPTION OF THE COUNTRY BETWEEN 
I now proceed to give the facts I have gathered by observation and inquiry upon 
this subject, taking the Blue Limestone of Cincinnati as the geological horizon for 
comparison. Mr. Lapham has observed rocks of this age in the valley of Rock 
River, a few miles north of Lake Koshkonong, in Range 13 east, Township 6 north, 
Jefferson County, and again in Dodge County, in the same range in the east part of 
Township 10 north, they crop out to the westward, occupying a belt of about a mile 
in width, and consequently the thickness cannot be great. The same formation is 
seen on the eastern shore of Green Bay, at Little Sturgeon Bay, Township 27 north, 
Range 14 east, at the level of Lake Michigan. Between these points, about one 
hundred and twenty miles apart, I am not aware that it has been traced, or even 
seen, unless some of the bluish-green beds of limestone, about Lake Winnebago, and 
on Fox River, that I shall soon notice, are the equivalents of this formation. Dr. 
Houghton examined and laid down the same rock on the west and north shore of 
Green Bay, around the head of Little “Bay de Noquet” (pronounced Ba-de-nok), 
in Michigan. 
The three points which I have noticed where this limestone makes its appear- 
ance, are nearly in a right line, which bears about northeast by north. The surface 
of the country on this line, from Jefferson County, rises to the east and northeast ; 
but to the left or westward of it, around Lake Winnebago, and in the valley of the 
Fox River, there is a depression, along which the outcrop of the blue limestone may 
well be expected, curving to the northwest of the direct line between the present 
known points of outcrop. 
I have selected the Blue Limestone as a starting-point from which to reckon each 
way up and down the series, because in Eastern Wisconsin it is the bed about 
which all geologists will best agree as to its position. 
To show more forcibly the difficulties that exist in the present state of our exa- 
minations, in arranging these rocks, I will give the results of examinations made in 
the Silurian strata, both on the east, in Michigan and in Canada, and on the west, in 
Wisconsin. It should likewise be remembered, that neither the Michigan nor the 
Eastern Wisconsin surveys are complete or fully reported upon, and therefore the 
lights that are derived collaterally from these sources are not only not full, but 
subject to future modifications. 
The New York system of rocks has now been traced from Virginia through 
Pennsylvania, and through New York, Canada, Michigan, Wisconsin, and Minnesota, 
leaving its vast area indeterminate on the west and northwest. We are therefore 
considering a portion midway between its extremes. A comparison of sections 
showing the order and nature of these beds, at different points, both east and west, 
and also of the region under consideration, may be useful and interesting. 
A glance at the tabular arrangement, on the next page, of the rocks, as different 
observers have reported them, shows that although other beds change or disappear, 
the equivalent Blue Limestone of Cincinnati runs from the eastern part of Michigan 
to the western part of Wisconsin. Doubtless there are some imperfections in the 
grouping of the various formations by different authors, but a striking uniformity 
pervades the sections when we regard the broad space which they represent. : 
