292 5. WEI DM AN 



developed in only one way; namely, by the process of degrada- 

 tion of a pre-existing mountainous region. 



Discordance of land surface and rock structure of other 

 regions like that of this pre-Cambrian area has been so adequately 

 explained and so generally accepted by geologists for the last 

 two or three decades, as the resultant of long-continued erosion, 

 that it seems reasonable to conclude at once that the sloping, 

 flat-topped uplands about Wausau are the remnants of what was 



Fig. 3.^View of the beveled pre-Cambrian rocks on the west side of the Wiscon- 

 sin river one mile south of Stevens Point. This is at the border of the sandstone and 

 crystalline districts, and here the level of the river practically coincides with the level 

 of the ancient peneplain. The view shows decomposed gneiss overlain by the river 

 sand and gravel, the sandstone and residual clay having been eroded. On the oppo- 

 site bank of the river sandstone caps residual clay, the latter grading down into the 

 partly decomposed gneiss. 



formerly a nearly level land surface due to the wearing down by 

 erosion of a once mountainous region to an approximate plain. 

 The mountain folds of the pre-Cambrian have been cut off by 

 erosion at the even sky-line of the area, just as the fibers of a 

 great tree are cut across at the even surface of its sawed stump. 

 The complete degradation of the mountains was not accom- 

 plished, as is evidenced by such isolated hills as Rib hill and the 

 Mosinee hills which project above the flat-topped uplands, and 



