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 whitish 
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 Plerinea. 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 Pentamerus 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 Katon. 
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 
