420 GEOLOGY OF CENTRAL WISCONSIN. 



In this last section of its course tlie Wisconsin is much obstructed 

 by bars of shifting sand derived originally from the erosion of the 

 great sandstone formation which underlies the whole region, and to 

 whose existence the unusual amount of obstruction of this kind in 

 the river is due. The peculiar instability of these sand bars, and 

 their liability to form and disappear within a few hours, renders their 

 control very difficult. In view of the enormous quantities of this al- 

 ready disintegrated sand in the region drained by the river and its 

 tributaries, many of which have their entire course through sand dis- 

 tricts, the construction of a continuous canal along the Wisconsin 

 river from Portage to its mouth, would appear to be the only way 

 to utilize the natural highway from the lakes to the Mississippi 

 which is offered by this and the Fox rivers. In the last section of its 

 course the Wisconsin receives within the limits of our district only 

 one stream of importance, the Baraboo, which enters the river 

 near the easternmost point of its great bend.. Heading in the adja- 

 cent corners of Monroe, Yernon and Juneau counties, at an elevation 

 of about 400 feet above its mouth, the Baraboo runs southeastward 

 into Sauk county, where it breaks into the valley between the two 

 east and west quartzite ranges already alluded to, through a narrow 

 gorge in the northern range. Turning then eastward- it runs along 

 the middle of the valley between the two ranges for about fifteen 

 miles, and then, breaking again northward through the north range, 

 follows its northern side east to the Wisconsin. The Baraboo is a 

 stream of very considerable size, and yields a number of excellent 

 water powers in the valley between the quartzite ranges, having a 

 fall on this portion of its course of seventy feet. The tributaries on 

 the south side of the Wisconsin, in this section of its course, are of 

 little importance, owing to the nearness of the limestone divide. The 

 most noteworthy is Duck creek, which with its branches drains a 

 considerable area in the towns of Pacific, Springvale and Courtland, 

 in Columbia county, cutting a long way back into the divide. 



