UNION MORAINE. 489 



time the Union moraine was forming, if we may judge from the size of the 

 gravel plain, for it occupies at its head an area of several square miles. 

 The thickness of the gravel deposit is but a few feet, there being rock at 

 slight depth over much of the region upon which it rests. Places were 

 observed near the borders of the moraine where the gravel is underlain by 

 till at a depth of 12 to 15 feet. The altitude of the gravel plain at its 

 head is nearly as great as that of the bordering till plains south of the 

 moraine, and is at Covington 50 to 60 feet above the bed of Stillwater 

 River, the stream here being in a narrow rock-bound gorge. 



Grreenville Creek also has a narrow gorge up to Grreenville Falls, about 

 one-half mile above its mouth. Its bed above the falls is mainly in the drift 

 and its valley is less restricted and varies considerably in width. The gravel 

 plain just described extends up Green\'ille Creek 2 miles or more and rem- 

 nants of glacial gravel are found almost the entire length of the creek, but 

 they are less conspicuous than the gravel plain near its mouth. The phe- 

 nomena seem to indicate that the creek adopted its course along the outer 

 border of the moraine because of a valley opened by glacial waters. 



White River Valley carries but little gravel and has scarcely a sign of 

 a glacial terrace along the portion which borders this moraine, its bed 

 being but 10 to 20 feet below the bordering plain. It seems therefore to 

 have been a subordinate line of discharge for glacial waters. 



On the Mississinawa no terrace was noted which seemed to connect 

 with this moraine. 



INNER BORDER PHENOMENA. 



The narrow tract lying between the Union and Mississinawa moraines, 

 a tract nowhere exceeding 8 miles in width, consists mainly of a smooth- 

 surfaced till plain on which the drift has nearly as great thickness as on the 

 moraine into which it merges on the south. Two esker belts appear on 

 this plain, one in Logan County, Ohio, between Richland and Huntsville, 

 which is called the Richland esker; the other in Delaware County, Ind., 

 leading frohi the vicinity of Greenville nearly to Muncie, which is called 

 the Muncie esker. 



THE RICHLAND ESKER. 



The northern end of the Richland esker is immediately west of that 

 village, from which point it extends in a south-southwest course for more 

 than a mile without any serious interruption, and is continued in a chain of 

 short ridges, with frequent gaps for nearly a mile farther. It lies in a valley 



