208 PLEISTOCENE OF INDIANA AND MICHIGAN. 



lobes is about 800 feet. The waters passed southward along the eastern front of the Lake 

 Michigan lobe to Plainwell and there joined the longer line of glacial drainage just described. 



With the northward extension of the reentrant angle between the Saginaw and Lake Michigan 

 lobes, past the city of Grand Rapids, and a slight westward shrinkage of the border of the 

 Lake Michigan lobe a line of glacial drainage with bed below the 700-foot contour, well shown 

 on the Grand Rapids topographic sheet, was opened southward from Grand Rapids past 

 Carlisle and Ross to Rabbit River. 



With the recession of the reentrant into southwestern Montcalm and southeastern Newaygo 

 counties the glacial drainage took a southward course between the ice lobes for a short distance 

 and then turned into districts which had just been abandoned by the Lake Michigan lobe. (See 

 pp. 220-221.) 



INNER BORDER. 



GENERAL CHARACTER. 



The interval between the Charlotte morainic system and the next later moraine of the Saginaw 

 lobe is filled principally by a till plain, whose surface is in large part very smooth and much of 

 which is included in the Lansing, Mason, Fowlerville, and Howell quadrangles. In Ingham 

 and Livingston counties, however, it is traversed by several eskers, which lie for the most part 

 in shallow swampy depressions or esker troughs and which lead somewhat directly toward and 

 terminate hi the morainic system. Some of these swampy depressions are not occupied by 

 eskers or are occupied by them for a part of their course only. 



On this inner border tract there are a few very prominent knolls and some undulating strips 

 nearly surrounded by till plains. Some of these knolls northeast of Howell are elongated in 

 the direction of ice movement and form short chains, as is the habit with eskers, but are irreg- 

 ular in shape, in some places reaching a width of nearly one-fourth mile. They are clearly 

 shown on the Howell topographic sheet in sees. 16, 17, 20, 21, 28, and 29, Oceola Township. 

 Though composed largely of gravel and sand they are partly veneered with bowldery till. Their 

 height is from 60 to 100 feet. The longest chain, which extends from the north part of sec. 16 

 southwestward into the edge of sec. 20, has a length of about 1J miles. The chain in sees. 21 

 and 28 is less than a mile in length and so also is the chain in sec. 29. 



A rather conspicuous undulating strip about a mile wide with swells 10 to 30 feet high 

 runs east and west through northern Barry and Eaton counties a few miles south of Grand 

 River, Roxana being on it. In places it is nearly in contact with the Charlotte morainic system 

 and in places is separated from it by a till plain 2 to 5 miles wide, and it appears to merge at 

 both ends in that morainic system. Farther east in northwestern Ingham County an undulating 

 strip leads from the Charlotte morainic system at the bluff of Grand River northeastward past 

 Holt to the Cedar Valley east of Okemos. The knolls in it are, however, low and scattered 

 and parts of the strip are difficult to differentiate from the bordering till plains. These strips 

 have in places some resemblance to the slender and in places ill-defined members of the next 

 morainic system, and may perhaps belong with that system. 



The surface of this inner-border tract is generally plane, but wells indicate that the under- 

 lying bedrock surface is very uneven, the depth to rock ranging from 20 feet or less to about 

 200 feet. 



DISTRIBUTION OF ESKERS. 



As already indicated, small eskers a fraction of a mile in length are found in many of the 

 transverse depressions which characterize this morainic system from the vicinity of Hastings 

 eastward across Eaton, Ingham, and Livingston counties. Other longer eskers or esker systems 

 lead from the inner border district southward into the morainic system. These long eskers 

 lie in valleys or troughs throughout much of their courses in the till plain as well as in the 

 moraine. These valleys or troughs are in places nearly as narrow as the esker ridge, but com- 

 monly they are several times as wide. Some of the depressions are occupied for only a portion 

 of their length by an esker; the association of esker ridge and trough is, however, so close as 



