372 ARTHUR C. TROWBRIDGE 



until the gap was entirely filled and the pre-Paleozoic topography 

 was buried deeply. (7) The seas finally withdrew, stream courses 

 were developed and superimposed upon the old topography and 

 structure, and a peneplain was developed, probably in late Tertiary 

 time. (8) This peneplain was uplifted about 200 feet, and a second 

 partial peneplain was developed. During this erosion cycle the 

 Wisconsin River adjusted itself in the old gorge, and a valley about 

 300 feet deep was formed. (9) Another uplift to an amount of 

 about 600 feet resulted in renewed erosion and the deepening of the 

 gorge from 300 feet to 900 feet or more. (10) In the northern por- 

 tion of the renewed gorge so formed, an ice barrier lake was formed by 

 the edge of the Wisconsin glacier blocking the. valley at two points. 

 This lake received much glacial water, covered an area twice as large 

 as does the present lake, was at least 270 feet deep, and had an 

 outlet at 1,190 feet A.T., which drained northwestward, (n) With 

 the recession of the ice, the surface of the lake dropped to about 

 1,020 feet and then to 970 feet, as an outlet to the north was estab- 

 lished, and lowered through the terminal moraine dam. (12) Owing 

 to a diversion of drainage in the Steinke and Shubring basins, 

 decreasing the intake, and perhaps owing to changes in climate and 

 the establishment of underground channels, the surface of Devils 

 Lake fell from 970 to 960 feet, and the outlet was abandoned. 



