37° 



ARTHUR C. TROWBRIDGE 



There remains but one step in the pre-human history of Devils 

 Lake. Its outlet to the north has been abandoned. The reasons 

 for the sinking of the surface of the lake below the level of the outlet 

 may be several. With the gradual establishment of drainage in the 

 ground moraine of the Baraboo valley, a tributary to the Baraboo 

 River worked its way headward up the drift-covered slope of the 

 South Range and through the terminal moraine into the northern 



Fig. 6. — Sketch map showing the conditions of drainage around Devils Lake 

 after the diversion of water from the Steinke and Shubring basins and the abandon- 

 ment of the northward outlet. The endless line marks the boundaries of the drainage 

 basin of Devils Lake. 



portion of the Steinke flat, diverting the drainage from the east 

 and northeast, which up to this time had gone to Devils Lake, 

 to Baraboo River. Working rapidly in the non-resistant material 

 of the high Steinke surface, the stream developed a tributary 

 which worked back through the terminal moraine, tapping the 

 Shubring basin west of its original outlet. This diversion of 

 drainage resulted in a considerable decrease in the supply of water 

 for Devils Lake (compare Figs. 5 and 6) and doubtless helped to 



