132 GEOLOGY OF EASTERN WISCONSIN. 



lationship, and that the explanation is the same as that given for Pike 

 river — and that the same inference as to a southward lake current is 

 justified. 



We have a similar phenomenon in connection with the east mem- 

 ber of Two rivers, or the East Twin river, which marks, though 

 much less definitely, the western limit of the Upper Ked Clay, follow- 

 ing in a similar way the sandy beach deposit, that marked the shore 

 line of the lake at the time of its formation. It would seem then that 

 as far back as we can trace the history of the lake, by these means, it 

 has had a southward-flowing shore-current along the Wisconsin side. 



The coTirses of several other streams belonging to the Lake Michi- 

 gan system are to be explained in a similar way. 



The upper portions of the Wolf, Oconto, Peshtigo and Menomonee 

 rivers are essentially similar to each other. Rudely parallel among 

 themselves, they flow in the direction of the general inclination of 

 the surface, exhibiting nothing peculiar while they are passing over 

 the region of the granitic and other Archsean rocks, but after en- 

 tering upon the territory underlaid by Paleozoic formations, their 

 several directions become exceptional. 



The Oconto river, after flowing parallel to the Wolf for thirty-five 

 miles, turns at a right angle to the east, and flows directly to Green 

 Bay, while the Wolf river continues straight on its course for thirty 

 miles, when it turns with equal abruptness to the west, afterwards 

 more gradually to the south, and then east, and at Lake Winnebago 

 its current is reversed and flows northward, so that after a circuit of 

 about 140 miles, it reaches the mouth of the Oconto and mingles with 

 its waters, which have only traveled thirty miles since the rivers part- 

 ed company. 



The distance between the Wolf and Oconto where this divergence 

 takes place is only about twelve miles, more than half of which is oc- 

 cupied by Shawano lake and its outlet, and only drift accumulations 

 of no very considerable magnitude make up the divide. 



The Menomonee and Peshtigo rvvers make similar abrupt changes 

 in their direction. 



By referring to the map, showing the geological formations of this 

 region, the explanation of these anomalies becomes at once apparent. 

 It will be seen that the boundaries of the formations are zig-zag, or 

 step-like, and that the rivers follow the softer formations along the 

 face of these steps. 



The Wolf river, from Shawano south, follows along the nearer or 

 more remote cliffs of the Lower Magnesian limestone, its bed lying in 

 the soft Potsdam sandstone, until in the town of Ellington, along the 



