RIVER SYSTEMS AND GENERAL SURFACE SLOPES. 419 



Swerves around into the final soutliwestward stretch to the Missis- 

 sippi. The cause of this long detour to the east is sufficiently evi- 

 dent. As the river leaves the Dalles it finds lying directly athwart • 

 its course the two bold quartzite ranges which extend east and west 

 through Sauk county for upwards of twenty miles, and, crossing into 

 Columbia, finally unite about eight miles east of the county line, in a 

 sharp and bold, eastward projecting point, which rises 400 feet above 

 the river bottom. Above Portage, where the Wisconsin forms the 

 southern line of the town of Lewiston, the ground immediately north 

 is lower than the water in the river, the heads of Neenah creek, a 

 tributary of the Fox, rising within a short distance of its banks. In 

 times of high water the Wisconsin overflows into these streams, and 

 thus contributes much to a totally different river system. At Port- 

 age the Fox, after flowing south of west for twenty miles, approaches 

 the Wisconsin coming from the opposite direction. Where the two 

 streams are nearest they are but two miles apart, and are separated by 

 a low, sandy plain, the water in the Fox being five feet below that of 

 the Wisconsin at ordinary stages. The greater part of this low ground 

 is overflowed by the latter stream in times of high water, and to this 

 is chiefly due the spring rise in the Fox. After doubling the eastern 

 end of the quartzite ranges, as already said, the Wisconsin turns 

 again to the west, being forced to this by impinging on the north 

 side of a high belt of limestone country, which, after trending south- 

 west across tlie eastern part of Columbia county, veers gradually to a 

 westerly direction, lying to the south of the river along the rest of its 

 course. Soon after striking this limestone region, the river valley 

 assumes an altogether new character, which it retains to the mouth, 

 having now a nearly level, for the most part treeless bottom, from 

 three to six miles in width, ten to thirty feet in height, usually more 

 on one side than on the other, and bounded on both sides by bold and 

 often precipitous blufi's, 100 to 350 feet in height, of sandstone capped 

 with limestone. Immediately along the water's edge is usually a 

 narrow timbered strip — rising two to four feet above the river — which 

 is overflowed at high water. The line of bluffs along the south side 

 of the valley is the northern edge of the high limestone belt just 

 mentioned, which reaches its greatest elevations ten to fifteen miles 

 south of this edge. In front of the main bluff-face, especially in its 

 eastern extension, are frequently to be seen bold and high isolated 

 outliers of the limestone country. On the north bank the bluffs are 

 at first the edges of similar large outlying masses, but further down 

 thpy become more continuous, the river crossing over the northwest- 

 ward trending outcrop line of the Lower Magnesian limestone. 



