450 



THE IRON RIDGE 



lime-rock like soil or diluvium. To the northward, the same appearances are ob- 

 served, and at about three-quarters of a mile, where the Wisconsin Iron Company 

 take out their ore, the hill appears to be all ore for sixty feet in height. The sur- 

 face ore is here mined almost as readily as sand or loose earth, only stripping the 

 soil and taking out the roots that are intermingled with it. But the upper and 

 external parts of the bed have evidently undergone movements, apparently some 

 great diluvial force, from the westward, pushing the outcropping mass up the hill, 

 wherever its face was not too bold. 



This impression is given by the lines of deposition, which are not horizontal, but 

 inclined and curved, following the form of the hill up and down along its western 

 slope. There are also lumps of clay or marl, resembling the tough marls associated 

 with the Cincinnati Blue Limestone, interspersed through the ore. As the excava- 

 tions become deeper, the loose portions will doubtless change to a more compact 

 and stratified mass, lower down the hill, like that seen at Sterling's Spring. I am 

 told the same ore is found at intervals along the bluff, but sinking towards the base, 

 along the heads of the Rubicon, southeasterly, to Hartford, a distance of about 

 twelve miles. 



The overlying limestone at Sterling's is a granular, gray, variegated Avhitish 

 and yellow limestone, that makes good white lime. I neither discovered or could 

 learn of any fossils in the lime-rock or the ore. The bluff extends northerly and 

 westerly ; and, at one and a half miles towards the furnace, presents a bold face of 

 thick-bedded limestone of one hundred feet perpendicular, the apparent dip to the 

 northeast, its base lower than the ore-bed, but no external signs of ore. The 

 rock, however, contains iron, which causes it to turn from yellow to red, when it is 

 heated in kilns. 



The same bluff may be traced northerly towards Fond du Lac, trending to the 

 northeast along the east shore of Lake Winnebago, in mural faces, and extending, 

 with little interruptions, parallel with Fox River, and along the eastern shore of 

 Green Bay to Sturgeon Bay. At the ore-bed, there are indications of an underly- 

 ing stratum of marl or calcareous shale, which may on examination prove to be a 

 member of the blue limestone. There is also in the bluff two miles north of Tay- 

 hedah, a soft stratum of a siliceous character, the fossils of which are very imper- 

 fect, but one is a Pterinea. These indications, when taken in connexion with the 

 vicinity of the blue or Trenton limestone, a few miles to the southwest of the bed, 

 point us to the " Clinton Group" of New York, or No. 5 of Pennsylvania, both of 

 them iron-bearing formations, as the geological equivalent of these Wisconsin iron- 

 beds. 



In New York, the strata of ore in this group are two, one below and one above 

 the Pcntamerus Limestone ; the lower one extending about twenty miles, as seen in 

 the County of Wayne, its greatest thickness about two feet, and highly fossilife- 

 rous. It is called an " oolitic" ore, with a greasy feel, by Mr. Hall, and a lenticular 

 or lens-shapen ore, by Professor Eaton. 



In Pennsylvania, there is in the same formation a deposit, from six inches to 

 twenty-four inches thick ; its outcrop extending, with intervals, from the Juniata 

 River, southerly, through Pennsylvania and Maryland, into Virginia, composed of 



