202 Wisco7isin Academy of Sciences, Arts, and Letters. 



nothing about minor undulations between Afton and Fulton, tbe 

 exposures about Beloit are so numerous that no considerable 

 undulations could exist undetected. 



The exposures represented iti the diagram do not all lie in a 

 direct line bj any means, but those which are of most interest as 

 indicating these marked undulations do lie almost exactly in a 

 north and south line. Hess' and Smith's quarries lie considerably 

 to the west of this line, but another small exposure to the east of 

 them, and more nearly in line, indicates almost exactly the same 

 slight dip as they. 



These outcrops all lie in the eastern face of the line of bluffs 

 which forms the western boundary of the present Eock river bot- 

 toms. As we have seen, the Galena limestone is only found 

 capping the highest hills. In the corresponding line of eastern 

 bluffs, whose height is about the same, the Galena limestone is 

 everywhere found, and the Trenton occurs only in the bottom of 

 a deep ravine at Turtleville. This shows that the dip is prevail- 

 ing eastward, which is to be presumed, since Beloit lies in the 

 eastern slope of the north and south geanticlinal axis, which 

 made Wisconsin the oldest state of the American continent, if not 

 the oldest in the Union. The crest of this great geanticlinal runs 

 down to the west of Beloit, giving our strata a slight slip to the 

 east, amounting to about twenty-five feet in the five /'niles between 

 the limekiln and the ravine at Turtleville. The undulations 

 already traced are, therefore, of the nature of small anticlinal 

 ridges and synclinal valleys crossing the main geanticlinal axis of 

 Wisconsin. They are, of course, very small compared with it, but 

 much more abrupt. The existence of similar, but much more 

 extensive, humps on the camel's back is indicated by the fact that 

 in two localities further south, in Illinois, the St. Peters sandstone 

 comes to the surface ; at Beloit it drops about to the river level ; 

 at Rockton the river runs over Treuton limestone ; at the 

 rapids south of Roscoe I have not seen the exposure, but from 

 the rock and fossils I judge that it cuts through either the Lower 

 Blue or, more likely, the Birdseye beds. But in Ogle county, 

 Illinois, although the river is not at all abrupt to this point, the 

 sandstone is found far above the river. A similar area is mapped 

 by Worthen further south, in Illinois. 



