Geological Excursion into Central Wisconsin — Hall. 267 



folded and displaced, are still elastics in every character; on the 

 other hand, the schistose character is so predominant as to oblit- 

 erate all genetic characters. Typical examples of the first type 

 appear in the northern part of Waiisan city, where silicious schists 

 have been cut through both by river erosion and by railway con- 

 struction; examples of the other extreme of the series, equally 

 typical, can be seen along the Trapp river and at the bend in the 

 Wisconsin river a mile below Merrill. 



In external aspect the rocks above Wausau are firm and com- 

 pact, very finely crystalline, and strictly speaking they are not 

 schists. They vary considerably in color, being in places, as on 

 the west side of the river near the upper mills and opposite the 

 city waterworks, of a reddish hue, which within becomes brown 

 and black with more or less mottling. Everywhere the rock is 

 greatly shattered; it is hard and brittle under the hammer and 

 breaks conchoidally. The texture is very fine, although in places 

 it assumes a greater coarseness and a very visible crystalline tex- 

 ture. Across the river towards the northeast the rock is very 

 finely textured, highly silicious and of the same hard, brittle and 

 conchoidal character. A banding occurs in the darker rock, 

 which, while obscure on the fresh fracture, is clearly seen on the 

 weathered surfaces. It is not regular either in continuity or di- 

 rection; often it is considerably contorted. Bands of conglomer- 

 ate lie in the rock. These bands, as represented by the exposure 

 in the cut nearest the Wausau station, show, for a conglomerate, 

 a medium coarseness aud so thorough a knitting together of the 

 pebbles that the granular character is almost wholly lost. The 

 strike of these beds is N. lO'^ E. magnetic. 



Microscopically the leading constituents of these rocks at and 

 to the north of Waifsau is quartz in very fine and brightly polar- 

 izing grains. In places more coarsely crystalline streaks appear 

 made up of a series of large interlocking individuals of quartz. 

 Biotiteis also a constant constituent; its folia are small and arran- 

 ged in bands or streams between layers composed almost of clear 

 quartz and its abundance marks the position of the darker bands of 

 the rock. In a few cases secondary individuals of microcline and 

 members of the plagioclase series were seen. Pyrite is almost 

 unfailing although its quantity is small.* 



A mile or two further north the rocks become quite markedly 



*Compare Irving and Van Ilise, Geology of Wisconsin, Vol. iv. p. CG8. 



