530 GEOLOGY OF CENTRAL WISCONSIN. 



added the fact that the country is largely unsettled, and covered by 

 heavy forests and swamps. The toriner spread northward of the 

 sandstone beyond its present limits is indicated by the occurrence on 

 the highest part of the dividing ridges of outliers of that formation, 

 100 to 200 feet in height, and also by the occurrence in the northern 

 drift of large quantities of loose sand. 



Notwitlistanding these diiHculties, it is believed that the boundary 

 line, as indicated on Atlas Plate XV, Area F., is not far from correct. 

 The principal facts upon which it is based may be here briefly stated. 

 On the east side of Area F., sandstone is seen in a small quarry on a 

 ridge on the west side of Plover river, on whose bank, just east, and 

 at points all along whose course to the mouth, the crystalline rocks are 

 exposed. From the quarry mentioned to Stevens Point, sandstone 

 appears to underlie the surface. At Stevens Point, it appears at the 

 top of the bank on both sides of the Wisconsin river, whose bed is on 

 crystalline rocks. A short distance north of Stevens Point, on the 

 road to "Wausau, and also on the road following the west bank of the 

 river, crystalline rocks are to be seen, and no sandstone is met with 

 further north. The Wisconsin Central Eailroad cuts through 

 sandstone at Stevens Point, but farther to the west and north 

 it is altogether on crystalline rocks, as shown by sereral cuts between 

 Stevens Point and Junction City. The Wisconsin Yalley Railroad, 

 from Knowlton, Marathon county, to Centralia, Wood county, is also 

 altogether on the crystalline rocks, which, for the most part, lie near 

 the surface, with very little drift covering. Along the east side of 

 the Wisconsin, below Stevens Point, sandstone 5 to 40 feet in thick- 

 ness is constantly to be seen in the east bank of the river, the crystal- 

 line rocks appearing in the river bottom as far as Point Bass, Sec. 15, 

 T. 21, K. 5 E., Wood county. At this point the crystalline rocks 

 disappear, and the sandstone in turn forms the river bed. ISTorth- 

 ward from Point Bass, along tlie west bank of the river, sandstone 

 shows again, at intervals, as far as Centralia. The Wisconsin Valley 

 Eailroad, north from Centralia, as already said, is always on the older 

 rocks, but a considerable thickness of sandstone occurs in a ridge on 

 the south side of Mosquito creek. Sees. 29 and 30, T. 23, R. 6 E. 

 Farther north, along the line between sections 7 and 8 of the same 

 town, small thicknesses of sandstone fill depressions between the 

 ridges. (3n the north side of the Wisconsin, between Mosquito and 

 Mill creeks, sandstone occurs at several points, but does not stretch 

 far north, for crystalline rocks are at surface over the northern parts 

 of T. 23, R. 6 and 7 E. Mill creek is altogether on the crystalline 

 rocks. Along the line of the Green Bay and Minnesota Railroad, 



