686 GEOLOGY AND TOPOGRAPHY OF THE LEAD REGION. 



from here to Scales Mound village it forms a continuous chain of hills, 

 among which the most noticeable is Charles Mound, which is the 

 highest land in the state of Illinois. This mound is capped with 

 about 50 feet of Niagara limestone, and in one place a quarry has 

 been opened, from which specimens of the fossil Favosites favosa 

 have been obtained. 



The average dip of the strata, in the vicinity of Scales mound is 

 about 22 feet per mile in a southwesterly direction, with indications 

 that it is not perfectly uniform but slightly undulating as represented in 



FIG. 10. 



SECTION FROM SCALES' MOUND TO THE STATE LINE. 

 1 Cinncinnati Group. 2 Galena Limestone. 



The Cincinnati group next appears about the Platte Mounds, in the 

 southern part of T. 4, R. 1 E, and the northern part of T. 3, R. 1 

 E. In T. 4, E. 1 E., it is found in Sees. 31, 32, 33, 34, 35, 36, cov- 

 ering an area of nearly three square miles, and reaching an elevation 

 of 1,140 feet above the sea. 



The formation also exists in its full thickness at the Blue Mounds, 

 but exposures of it either natural or artificial are seldom visible; 

 some of the clay which characterizes the lower part of the formation 

 was found on the Brigham farm at the East Mound. 



No exposure of this formation was found at these localities. la 

 passing over the gradual slope of the mounds it is impossible to dis- 

 tinguish any boundary line between the Cincinnati group and the un- 

 derlying Galena limestone, such as is seen on the level table land 

 south of Shullsburg, which has been formed by the denudation of the 

 soft shales which the harder limestone has to a great extent escaped. 

 The line of demarkation between the shales and the overlying Niag- 

 ara limestone, is well defined at the West Platte Mound on all sides 

 by the very marked change from the steep slope of the limestone to 

 the comparatively gentle one of the shales. On the north side of 

 this mound, ledges of the Niagara limestone may be seen in place 

 almost to the bottom of the formation. 



The Cincinnati group was also found covering about seven square 

 miles of country, about the Sinsinawa Mound, in the following sec- 

 tions: 1,12, 13, 14, 24, 25, 26, 35, 36, T. 1, E. 2 W. Sees. 6, 7,. 8, 16. 

 17, 18, 19, 20, 29, 30, 31, T. 1, E. 1 W., extending north from the 



