646 GEOLOGY AND TOPOGRAPHY OF THE LEAD REGION. 



details of which, belonging to each separate locality, could be more 

 easily and intelligently obtained in the progress of the survey of 

 this and the succeeding year. Further, it was necessary for topo- 

 graphical purposes to ascertain the elevation of numerous points, 

 which should be readily accessible to the various parts of the region, 

 as will be more fully explained under the subject of Barometrical 

 Observations. 



The greater part of the summer of 1873 was devoted to these pur- 

 poses, and spent within the confines of the Lead region, with the 

 exception of the latter part of July, and two \veeks in August, which 

 were passed in the counties of Sauk and Richland, in the examination 

 of the Potsdam and Lower Magnesian formations, and the iron ore 

 deposits incidental thereto. 



Survey of 1874. The territory examined in that year was as fol- 

 lows: 



Towns 1, 2, 3, 6, 7, 8, - 

 " 2,3,6,7, - - 

 " 2,3,6,7, - - 

 "3,6, 



" 1, 2, 3, 6, 7, 8, - 

 " 1, 2, 3, 4, 

 " 1,2,3,4, - 



The townships here enumerated comprise the northern and south- 

 ern parts of Grant county, the eastern and western parts of La Fayette 

 county, the western part of Iowa county, and that part of it which is 

 drained by Mill creek, the whole of Green county, the western part 

 of Bichland county, and some parts of Yernon, Monroe and Jackson 

 counties. 



The field work was commenced on the 14th of May, 1874, nearly 

 three weeks earlier than in 1873. The total area examined is equal 

 to sixty-six full townships, being an increase of sixteen over the pre- 

 vious year. 



The first examinations were made in the vicinity of Cassville, pro- 

 ceeding eastward from there to the eastern boundary of Green county, 

 and visiting successively all the mining districts and individual 

 mines, of which a full report will be found in chapter IY. After 

 examining the Mill creek district, the survey next proceeded to range 

 two west, north of the "Wisconsin river, including the valley of Knapp 

 creek and the upper Kickapoo, and as far north as the Green Bay & 

 Minnesota railroad. Finally returning from there, the northeastern 

 part of Iowa, and the northern part of Grant counties were examined, 

 together with that part of the valley of the Wisconsin winch lies 

 south of the river. 



