348 ARTHUR C. TROWBRIDGE 



THE EARLIEST RECORD 



The history of the depression in which Devils Lake lies goes 

 back to pre-Cambrian times. Cambrian sandstone lies in the gap, 

 (i) at the north end of the east bluff one mile south of the northern- 

 most outcrop of quartzite in the South Range, 240 feet above lake- 

 level and 270 feet below the summit plain; (2) near the foot of the 

 west bluff, one-fourth mile north of the north end of the lake, 60 

 feet above lake-level and 450 feet below the tops of the bluffs; 

 (3) at the southwest corner of the lake at " Messenger's End," 

 where it extends from a few feet above lake-level to an altitude of 

 1,200 feet at the divide between Devils Lake and Skillett's Creek; 

 and (4) forming a hill or bluff on the north wall of the gap 2\ miles 

 east of the lake. At the last-designated point the sandstone 

 extends to 900 feet A.T., which is below lake-level. The presence 

 of Cambrian sandstone at levels near that of the present lake 

 surface, near the north end, near the southeast end, and near the 

 center of the gap shows clearly that there was a depression or that 

 there were depressions here before the advance of the Cambrian 

 sea. The facts might be interpreted in one of two ways: 



1. The simplest explanation lies in the assumption that after 

 the pre-Cambrian formations were folded, the surface was eroded 

 and reduced to a peneplain on which a river meandered, that this 

 plain was uplifted relative to the sea, and that the district had 

 reached late youth or early maturity in a second cycle of erosion 

 before submergence by the Cambrian sea. Under this interpre- 

 tation the original gap is a pre-Cambrian intrenched meander. 

 The ancient peneplain may be represented by the present summit 

 plain of the district, or it may have been entirely destroyed in sub- 

 sequent periods of erosion. 



2. The conditions, however, might be almost equally well 

 explained by assuming that the district was in maturity either of 

 its first or of some later cycle of erosion when the Cambrian sea 

 advanced, that at that time a deep valley existed in the range with 

 its head in the valley of Messenger's Creek and discharging east- 

 ward and southeastward, and that another stream headed some- 

 where north of Messenger's Creek and flowed northward into the 

 Baraboo valley. This would not necessitate more than one cycle of 



