468 GEOLOGY OF CENTRAL WISCONSIN. 



bedding. A red felspathic vein was noted, 2 inches wide, dipping 70 N., and also the 

 same east and west quartz veins as before. Towards the northwest end of this ex- 

 posure the gneiss is quite thoroughly decomposed into a crumbling, earthy- textured, 

 brown- and white-blotched material, showing still a few mica flakes and quartz granules 

 in the interior, and containing 4.96 per cent, of water. The same partly kaolinized 

 rock is found all along the section until the west bank of the river is reached, showing, 

 however, still quite plainly the lamination and bedding planes of the unaltered rock, the 

 dip and strike remaining the same. At the foot of the west bank, which is about 20 

 feet in height, unaltered quartzose granite shows, with north and south quartz veins % 

 inch thick. Above this, and some few feet above the water level, fine, white, soft kaolin 

 shows in a little swamp, and above this again are seen a few thin layers of the sand- 

 stone. 



On the N. W. qr. Sec. 10 are openings in the river bank, here some 20 feet in height, 

 showing a considerable quantity of white kaolin. The various exposures are at differ- 

 ent levels, and may indicate a thickness of as much as 15 feet in some places, but as the 

 clay is merely an alteration of the gneissic rock in place, it forms no continuous bed, 

 the less altered portions of the rock occasionally rising entirely through it. At the 

 principal opening 22 inches of soft, bluish-white clay were noticed. The following are 

 analyses of samples from this place: 



861. 862. 



A B 



1.51 1.54 

 .81 .22 



1.17 



861 A is the raw kaolin from the lower part of the exposure; 861 B is the fine or ka- 

 olinite portion of 861 A, separated by levigation. Nos. 862 A and 862 B are, in like 

 manner, raw and washed clay from the upper part of the same opening. The amounts 

 of alkalies are considerable, and no lessening in their percentages appears to be effected 

 by levigation. The state of oxidation of the iron was not determined, but it would ap- 

 pear to be chiefly in the protoxide state, judging from the color of the clay. These facts 

 would indicate a less thorough kaolinization here than at other places in the vicinity. 

 Immediately above the kaolin openings are two feet of coarse, brownish, friable sand- 

 stone, whilst below it, down to the water's edge, gneiss in decreasing stages of decom- 

 position is seen. At the foot of the bank is a low exposure of unaltered, fine-grained, 

 light-colored gneissoid granite (868). The three ingredients of the rock are all distinctly 

 visible, the felspar being both pink and white, the latter without apparent striations; 

 the quartz is abundant, in hyaline grains; the mica is aggregated into layers and pro- 

 duces a greasy feeling on some surfaces of lamination. 



At the foot of the rapids, on the west side of the Wisconsin, just above Port Edward, 

 on Sec. 25, T. 22, R. 5 E., a rather coarse grained, mottled, red-weathering gneissoid 

 granite (879) is exposed. A distinct parallel grain is perceptible, with corresponding 

 bedding joints, which strike N. 45 E. and dip 50 N. W. Other joints, which make 

 large smooth faces, strike N. 75 E. About 50 feet further up stream is exposed a coarse- 

 grained, pinkish, highly felspathic rock, which shows a very distinct, sometimes con- 

 torted, lamination, trending in the same N. 45 E. direction as before. In this rock 

 the mica is nearly excluded by the felspar and quartz, which themselves are largely 

 separated into distinct bands. In places much pyrite is present. Fifty feet further a 

 low exposure shows an apparent JN . 50 W . strike, but this seems to be due to numer- 

 ous close veins running in this direction, for a few feet beyond, the same strike direc- 

 tion as before observed reappears, accompanied now by a southeast dip, in a fine 



