328 GEOLOGY OF EASTERN WISCONSIN. 



below, which constitutes a reason for not grouping the iron beds with 

 the Cincinnati series. 



Within the limits to which strati graphical evidence thus confines 

 this formation, there can be no hesitancy in referring it, on litholog- 

 ical grounds, to the Clinton epoch, since that epoch is characterized 

 from Ohio as far eastward as Nova Scotia, and as far southward as 

 Alabama, by a similar deposit of oolitic iron ore. 



As this formation is developed only at certain localities, we may 

 profitably omit further general remarks, and give place to detailed 

 local descriptions. 



By far the most important development of this formation occurs at 

 Iron Ridge, in the township of Hubbard, Dodge county. The main 

 deposit is included in Sees. 12 and 13 of that town. The locality is 

 characterized by a north and south ledge facing the west, and over- 

 looking the lower land in that direction, from a height of about sixty 

 feet. . The upper twenty feet or more of this ledge is composed of 

 heavy, rough beds of Niagara limestone. Beneath this lies the ore 

 bed having a varying thickness, the average of which is perhaps fif- 

 teen to eighteen feet. 



This leaves the base of the ore at a most convenient elevation above 

 the lower land adjoining on the west, giving the most ample facil- 

 ities for drainage, loading the ore into cars, or supplying the ad- 

 jacent furnace. The accompanying topographical map, for the data 

 of which, as well as many other favors, I am indebted to the kind- 

 ness of Supt. W. C. Sterling, will show the situation more precisely, 

 and the chromo-lithograph (PL X), which has been accurately 

 sketched from a photograph, will give a more vivid conception of the 

 relations of the ore and the method of mining, than can be conveyed 

 by description. The mine, of which only a small portion is shown 

 in the plate, is situated a short distance west of the center of Sec. 13. 



Near it is the furnace, and a little further west is the village. 

 Three-quarters of a mile north of this, is the Mayville mine, on what 

 is known as the Mayville Ore Bed, though the village of Mayville is 

 four miles and a half distant. The working force at this point, at the 

 time of my investigations, was in charge of G. K. Hood, to whom I 

 am indebted for various favors. 



Having thus before us the essential geographical features of the 

 location, and the general situation of the ore bed, we may give our at- 

 tention more specifically to the deposit itself. 



The ore occurs in regular horizontal beds, varying from about 3 to 

 14 inches in thickness. The dip is slight and varying in direction. 

 Near the furnace, it is northward; at the Mayville Ore Bed, it is south- 



