352 
The American Geologist 
June, 1890 
have also seen that professor Hall compares the exposure to 
that of Cincinnati and Madison, and it is generally recognized 
as the direct extension of the shales of the Maquoketa River. 
In the year 1862 professor J. D. Whitney'^'* mentioned the 
strata of Paige's Mound in Jo Daviess county, in the north- 
west corner of Illinois, as "a soft, yellowish, magnesian lime- 
stone, with graptolitic markings, and a considerable number 
of fragments of .-I.sajj/i't.s! (/iso((^^(<.*) f/iV/<t.s. These strata on the 
summit of Paige's mound are identical with a portion of the 
series observed farther south at Savannah." 
We present below in a tabular form the main facts as ascer- 
tained in those counties in Illinois, which relate to the Cincin- 
nati rocks : 
Counties. 
Q 
Thickness. 
Iroquois 
feet. 
feet. 
Out of line of section. 
Out of lineof section . 
outcropping. 
300 
0-388 

0-70 

Absent. 




213 
20 
100 
71 
TrentOL 
30 
37 
80 
120 
Kankakee 
Will 
Grundv 
Kendall 
LaSalle 
Lee 
Whiteside 
Carroll 
Jo Daviess 
Thus we see that from the last station in Indiana with an 
estimated thickness of 300 feet, and a depth below the surface 
of 500 feet and over, the group rapidly diminishes in thickness 
to 213 feet and 100 feet, and then disappears, while at the same 
time it rises from over 500 feet below, up to the surface itself. 
Reappearing again, however, in the course of a few miles and 
increasing from 30 feet to 120 feet in Illinois, and to probably 
200 feet in places in Iowa. 
Thus we have traced the rocks of Cincinnati age almost 
without a break from Richmond, Indiana, to Savannah, Illi- 
nois, and have demonstrated that the Maquoketa series is an 
extension of the Cincinnati group. It will now be necessary 
to examine the fossil remains from the exposure in Iowa, 
and see to what extent they differ from those at Cincinnati 
-'Geology of Illinois, vol. 1, p. 138, 1866. 
'•'^Geology of Wisconsin, vol. 1, p. 182. 
