THE HISTORY OF DEVILS LAKE, WISCONSIN 371 



cause the lake surface to sink below the level of its outlet. Con- 

 ceivably also the advance of the post- Glacial epoch was attended 

 by increasing temperature and increasing evaporation and by 

 decreasing precipitation, so that more water was lost by evaporation 

 than was supplied by precipitation. And perhaps the time came 

 when underground lines of drainage were established in the gravel 

 and sand of the drift, through which enough water was carried from 

 the lake to cause its surface to subside. Doubtless all these factors 

 and possibly others contributed to the lowering of the surface of the 

 lake and the abandonment of its outlet. 



With the abandonment of the outlet, the stream from the Peck 

 basin, which had flowed into the lake or into its outlet, chose the 

 easier of two possible routes, avoiding the lake and flowing down the 

 valley of the old outlet to Baraboo River. A few years ago, in 

 order to prevent floods in its lower course, this stream was diverted 

 again to Devils Lake by the building of a dam and the digging of a 

 shallow ditch connecting the stream with the lake. Today the stream 

 flows into Baraboo River or into Devils Lake, according as the 

 temporary dam is located in the stream channel or in the artificial 

 ditch. 



The lake of today has a maximum depth of only about 40 feet, 

 covers an area of only a little more than | square mile, and is without 

 an outlet. Its drainage basin at present is shown in Fig. 6. 



SUMMARY 



Devils Lake is seen to have had a long and complicated history. 



(1) Pre-Cambrian rock formations were deposited and folded. 



(2) Across the edges of the beds a peneplain probably was formed, 

 over which a large stream meandered. (3) An uplift seems to have 

 occurred and the stream intrenched itself, making a deep, curved 

 gorge through a ridge of quartzite. (4) An early Paleozoic sea 

 advanced over a surface of high relief and great irregularity, par- 

 tially, but not completely, filling the pre-Cambrian gorge with 

 sediments. (5) This sea withdrew at the end of the Prairie du 

 Chien epoch, leaving a sag where the old gorge had been. (6) Condi- 

 tions favoring deposition in the sea, and perhaps deposition by wind 

 temporarily and locally, were renewed and deposition continued 



