i:)RIFT PHENOMENA IN WISCONSIN 14I 



can be no doubt that the gorge between the east and west bluffs 

 was originallv the work of a pre-Cambrian stream, though the 

 depth of the pre-Cambrian valley may not have been so great as 

 that of the present. Later, the valley was filled with the Cambrian 

 (Potsdam) sandstone,^ and reexcavated in post-Cambrian and 

 preglacial time. Devil's Lake then occupies an unfilled portion 

 of an old river valley, isolated by great morainic dams from its 

 surface continuations on either hand. Between the dams, water 

 has accumulated and formed the lake. 



While the ice was at its maximum stand, it rose above the 

 moraine dams at either end of the lake. The melting of the ice 

 supplied abundant water, and the water of the lake stood above 

 its present level. The height which it attained is not known, 

 but it is known to have risen at least sixty-five feet higher than 

 now. This is proved by the presence of a few drift bowlders 

 lodged on the west bluff at this height. They represent the work 

 of a berg or of bergs which at some stage floated out into the 

 lake. 



TJic preglacial stream flozving through the DeviVs Lake gorge. — 

 The great gorge in the quartzite bluffs, a part of which is occu- 

 pied by the lake, was a narrows in the preglacial valley. If the 

 Baraboo was the stream which flowed through this gorge, the 

 comparable narrows in the north quartzite range — the Lower 

 Narrows of the Baraboo — is to be accounted for. The stream 

 which occupied one of these gorges probably occupied the other, 

 for the\' are in every way comparable except in that one has been 

 modified by glacial action, while the other has not. 



The Baraboo River flows through a gorge — the Upper Nar- 

 rows — in the north quartzite range at Ablemans, nine miles west 

 of Baraboo. This gorge is much narrower than either the Lower 

 Narrows or the Devil's Lake gorge, suggesting the work of a 

 lesser stream. It seems on the whole probable, as suggested by 

 Irving, ^^ that the Wisconsin River in preglacial time, flowed south 



'This fact was made known by Irvinc;, Geology of Wisconsin, Vol. II. Irving 

 also advanced the explanation here given, of the lake. 

 = Loc. cit., p. 508. 



