136 GEOLOGY OF EASTERN WISCONSIN. 



My attention was first called to those in "VValworth county some 

 years since by Dr. II. Hunt, of Beloit. The fluvial pairs and the 

 essential facts are briefly as follows: 



/. Geneva Lake and Big Foot Prairie, in Walworth county. The 

 bluffs on either side of Geneva Lake rise upwards of 100 feet above 

 its surface, but at its head the valley extends westward, though much 

 narrowed, and joins the more elevated level area, known as Big Foot 

 prairie, whose present drainage is southwestward, the watershed being 

 on its margin next Geneva Lake, and less than two miles from it. 

 The surface is more elevated on either side of the prairie, which bears 

 evidence of having formerly been occupied by a lake. 



2. Delavan Lake and the White river, in Walworth county. The 

 valley of Delavan Lake is very similar to that of Lake Geneva, but 

 it lies on the western slope. From it a well defined valley extends 

 across the divide and connects with the valley of White river, but the 

 elevation of the summit is greater than in the previous instance. 



j. Turtle creek and Sugar creek, in Walworth county. The head 

 waters of Turtle and Sugar creeks are connected by a narrow band of 

 marsh, bordered on the south by a line of bluffs, and on the north by 

 a more gentle ascent. Its whole aspect is that of a fluvial flat. 



4. The Bark and Oconomowoc rivers and the branches of Cedar- 

 creek, in Washington county. These streams constitute a double pair, 

 each of the rivers rising in a marshy valley in very close association 

 with the headwaters of Cedar creek, the elevations separating them 

 being very slight. 



5. Rubicon river and the northern branch of Cedar creek, in 

 Washington county. Between Cedar lake and the headwaters of the 



Rubicon river lies an elongated marsh, occupying a notable depression 

 in the otherwise elevated ridge. 



These facts naturally suggest the question, Did the streams on the 

 east side formerly flow across the present summit, or was the reverse 

 the case; or, again, are these facts to be otherwise explained? In 

 answer, it is to be remarked, in the first place, that the watershed in 

 question is either formed by, or is closely related to, the great drift 

 ridge previously described, and that this, as I shall hereafter attempt 

 to demonstrate, is a moraine, formed as an accumulation along the foot 

 of an immense sheet of moving ice. If this can be clearly pictured to 

 the mind, it will at once become evident that the waters from the melt- 

 ing ice mass must find their way across the accumulated drift, and as 

 the amount of water discharged must have been immense, deep valleys 

 would be cut at intervals of no great distance. This is probably the true 

 explanation of the initial formation of these valleys across the summit. 



