THE LOWER SILURIAN ROCKS. 597 



On the eastern side of the north and south quai-tzite range in Westflekl, T. 11 R 4 

 t-., m the eastern row of sections of that town, sandstone similar to that just described 

 occurs with a considerable tliickness. Certain layers at high levels are pecuhar in being 

 charged with the red and brown oxides of iron, which are at times in quantity suificient 

 to constitute an iron ore. This ore is to be seen in a pit on F. W. Schulte's land, S. W. 

 qr. of the S. E. qr. of Sec. l-S, with a thickness of about 10 feet. It is plauily stratified. 



^ and IS a more or less sandy admixture of the red and brown oxides of iron, the former 

 occasionaUy showing metallic surfaces, and greatly predoirdnating. The mner part of 

 the purer fragments presents a dark-colored, compact appearance, yielding a red streak. 

 Occasional stalactitic portions are to be seen, and some of the layers are almost without 

 iron oxide, consisting then of greyish sand with some greensand (glauconite) grains. 

 The following analysis (1269) is fi-om a sample averaged from the ore pile outside, and 



. covers all degrees of richness except the nearly pure sandstone layers: Sihca, 19.59; 

 alumina, 3.60; iron sesquioxide, 70.24; ma,nganese oxide, 0.54: hme, 0.76; magnesia, 

 0.04; phosphoric acid, 0.17; sulphur, a trace; water, 5.19 = 100.33: metalhc iron, 49.30. 

 Much of the ore of the pile is better than shown by the analysis, wloich itself represents 

 an ore of some value. The locality is worthy of close investigation, the in(Hcations be- 

 ing that a considerable quantity of a good "soft hematite " might be obtained. 



North of the quartzite ranges the Potsdam is everywhere the surface rock, making 

 frequent exposures, many of which are very interesting, but the space is not available 

 for their description. 



Dane County. 



(Atlas Plate XIII. Area D.) 



Dane is one of the lai-gest counties in the settled portions of the state, having a total 

 area of 1,237.84 square miles. Its shape is that of an almost perfect rectangle, the 

 northwestern comer of which is cut off by the Wisconsin river. From nortli to south it 

 measures 30 miles, including towns 5, 6, 7, 8 and 9; from east to west, 42 miles, includ- 

 ing ranges 6, 7, 8, 9, 10, 11, 12; tlius embracing 34 entire townships and one fractional 

 one. The western tier of townships, range 6, is included within the area of the lead 

 region, and will he found described in the report of Mr. Moses Strong. Tlie balance of 

 the county has an area of 1,080 square miles. 



Dane county has a position just about midway in the width of the state, its eastern 

 hne being 57 rrules from Lake Miclugan, and its western, 63 miles fsom the Mississipp'.. 

 Its southern line is 24 uules north of the Illinois state line. 



With the exception of an area of about 120 nules, in the northwest, that di-ains toward.? 

 the Wisconsin, the drainage of the whole county is shed southward and eastward 

 through different channels into Rock river. This result is due to the fact that nearly 

 the whole area hes on the south side of the Uraestone dividing ridge that linits the val- 

 ley of the Wisconsin on the soutli. This ridge enters the county on the north side of 

 tlie town of Vienna, trends thence south of west across Dane, and then, bending more 

 to the south, passes through the adjoining portions of Roxbury, Berry, Sprmgfleld, Mid- 

 dleton and Cross Plains, and leaves the county on the west side of the last named town. 

 The ridge has a general altitude of 500 to 600 feet, and a width sometimes of a whole 

 township, but on both sides is rendered quite irregular by erosion, the northern side 

 especially projecting in long, "bold points into the valley of the Wisconsin. The summit 

 of the ridge is largely occupied by prairie — a continuation of the prairie belt that char- 

 acterizes the same ridge in its passage across Columbia county — and has always, except 

 in Middleton and Cross Plains, the Lower Magnesiau as the suri'ace rock. In these 

 tovmsit rises into the St. Peters and Trenton horizons. In the nortliem portions of 

 Middleton, Crora Plains, Berry and Mazomanie the dividing ridge is cut entirely through 

 by a valley half a male to a mile in width, 18 miles in length, and 100 to 200 feet in 



