THE MARSEILLES MORAINE. 309 



RANGE IN ALTITUDE. 



The Marseilles moraine displays very little range in altitude. The 

 crest varies scarcely 25 feet from the 750-foot contour, and the lower parts 

 of the moraine stand near the 650-foot contour. Throughout much of its 

 course the 650-foot contour follows approximately the outer border of the 

 moraine. The inner border is somewhat higher, but as a rule falls below 

 700 feet. 



RELIEF. 



The above statements concerning range in altitude may be readily 

 applied in reference to the relief of the moraine. On the outer border it 

 averages about 100 feet; it is seldom less than 50 feet and in places reaches 

 125 feet. The relief on this border is least in the northern and the eastern 

 portion of the belt, in places being 50 feet or less. The middle portion, 

 except where combined with the weak inner ridge of the Bloomington sys- 

 tem (Farm Ridge), has a general relief of 75 to 100 feet or more. On the 

 inner border the relief seldom exceeds 50 feet, and for a few miles at the 

 north scarcely exceeds 25 feet. 



SURFACE CONTOURS. 



Throughout much of its course the Marseilles moraine has a well-defined 

 crest, and this, as a rule, constitutes a water parting. North of the Illinois 

 River it separates the tributaries of Fox River from those of Dupage River, 

 Au Sable Creek, and Nettle Creek. South of the Illinois it separates trib- 

 utaries of the Vermilion River from those of Mazon Creek and Kankakee 

 River. In eastern Illinois, however, it does not constitute an important 

 water parting, being crossed by the Iroquois River; and in western Indiana 

 it is crossed by tributaries of that river. The crest is sharpest for a few 

 miles in the central part of Kendall County, south and southwest of York- 

 ville, where it presents a narrow ridge standing 30 to 40 feet or more above 

 bordering portions of the moraine. Usually the crest is a broad, gently 

 undulating ridge 1 or 2 miles in width. Along the crest, as well as on the 

 slopes, there are saucer-like depressions containing water, except in seasons 

 of drought, and often occupied by clumps of willows. The swells are usually 

 low, seldom exceeding 20 feet in height, and have gentle slopes. However, 

 in parts of Livingston County, southeast of Odell, the swells in some cases 

 reach a height of 50 feet above sloughs inclosed among them. There is 



