56-i GEOLOGY OF CENTRAL WISCONSIN. 



however, occur, carrying its thickness up into the hundreds of feet, and bearing witness 

 to the great thickness which once must have existed over all the region. 



In Sec. 23, T. 21, R. 8 E., Portage county, on the edge of the great Plover marsh, 

 rises a prominent knob of sandstone, known as Mosquito Mountain. The bluff' is about 

 100 feet high, with its main extent east and west. Just west of it, on the west side of 

 the Portage and Stevens Point road, is a second lower knob. Near the base of the main 

 hill, the sandstone, as seen in a quarry (789), is rather line-grained and light-colored, with 

 brownish spots and laminae, and very friable indeed. It is composed of grains of limpid 

 quartz, that are all somewhat rolled, but are still subangular in shape, and has a very 

 minute quantity of a brownish cement. The bedding here is very distinct, the layers 

 running from. 2 inches to 1 foot in thickness on a quarry face of 15 feet. One hundred 

 yards to the east of the quarry, on the same hill, are ledges of a much coarser and more in- 

 durated sandstone (790), which is in places almost like quartzite, having a whitish color, 

 and composed of much-rolled grains of vitreous quartz, closely cemented. A similar rock 

 (791) occurs in small exposures up to the summit of the bluff. On the western bluff a 

 quarry exposes coarse-grained, brownish, moderately firm sandstone (792), having a 

 semi- vitrified appearance on the exterior. 



At the foot of Conant's Rapids, S. E. corner Sec. 8, T. 23, R. 8 E., 3D feet of hor- 

 izontally bedded sandstone show in the river bank, overlying gneiss. The lowest layers, 

 in contact vrith the gneiss, are hard and quartzite-like; but the body of the exposure is 

 thinly bedded, coarse-grained, friable, and of a light- brownish color. 



At Steven's Point, just below the railroad bridge, on the east bank of the river 

 (Plate IX, of Fig. 12), thin-bedded friable sandstone shows at the top of the bank, the 

 gneiss being exposed below. 



On the west side of the river, Sec. 31, T. 24, R. 8 E., is a low outlier of sandstone, 

 rising 51 feet above the river. The sandstone is cut into deeply at the south end of tho 

 mound, for the railroad, and this catting is expanded into a quarry at one point. 

 Another large quarry is worked on the northwest side of the hill. In the cutting, tho 

 upper layers are thin-bedded, whilst the lower seven feet is in heavy layers, and shows 

 a light brownish, white, much indurated, rock (774), of a medium grain, and composed 

 of highly glassy, subangular ; quartz grams. Fresh surfaces are quite uniform in ap- 

 pearance; weathered surfaces much iron-stained. Strong joints occur trending N. 15 

 W. and N 50 E. Pieces 4 by 4 by 4 % feet can be obtained easily, also thin slabs fit 

 for flagging, The quarry on the west side of the hill shows a similar stone, taken from 

 higher layers. The topmost layer in the quarry is very beautifully ripple-marked. The 

 stone from these quarries is a valuable one, and is much used in building at Stevens Point. 



About four miles north of Grand Rapids, in the town of Rudolph, S. E. qr. Sec. 20, T. 

 23, R. 6 E., Wood county, a large and excellent sandstone quarry has been opened near 

 the summit of the ridge, whose slope for half a mile southward shows sandstone ledges. 

 The quarry face is 20' feet, and shows very plainly bedded layers 1 inch to 2 feet in 

 thickness. These are traversed by very strong joints, trending N. 10 W. and N. 70 

 to 80 E. Some of the joints are inclined, especially the former set, most of which dip 67 

 W., and others are vertical. Ah 1 the stone is tolerably firm, but most of it is not unusually 

 indurated, crumbling easily in the fingers. Certain layers, however, are very highly in- 

 durated, and are susceptible of quite a high jpolish. These are both plain white and 

 white heavily streaked with dark red, are of a rather fine grain, and consist of sub- 

 angular grains of highly vitreous quartz. Large blocks can be obtained, as also thin 

 flags 10 by 18 feet. The stone is much used at Grand Rapids, and has a considerable 

 value. 



Along the Wisconsin river, from Grand Rapids to Point Bass, sandstone is fre- 

 quently exposed. Several sections in the vicinity of Grand Rapids, showing sandstone 

 overlying kaolin, have already been described. 



