506 GLACIAL FORMATIONS OF ERIE AND OHIO BASINS. 



full data concerning the character of the deposits in these channels. The 

 few exposures observed in the district, however, showed a pebbly clay, 

 which does' not differ perceptibly from the till of the moraines. 



OUTER BOEDER PHENOMENA. 



In northwestern Indiana the Mississinawa moraine, as interpreted by 

 the writer, is closely associated on the outer border with the great inter- 

 lobate Erie-Saginaw moraine, except for a few miles in Steuben County, 

 where a plain intervenes. This plain is traversed from north to south by 

 Pigeon River, and is commonly known as Pigeon River Valley. Its trough- 

 like form is, however, not a result of excavation, but was produced by 

 glacial accumulations on its borders, it being an intramorainic tract 

 bordered by ridges which give it the false appearance of having been 

 excavated. The width of this plain is 4 to 6 miles and the length 12 to 14 

 miles. Near its head are extensive gravel plains, and it is probable that 

 Pigeon RiA^er constituted an important line of discharge for glacial waters 

 at the time the moraine which borders it on the east was occupied by the 

 ice sheet. The breadth and the deep excavation of the portion of this 

 valley traversing the interlobate moraine give it every appearance of having 

 been occupied by a much larger stream than the present. 



The Wabash Valley probably constituted an important outlet for the 

 glacial waters at the time this moraine Avas forming, but the great enlarge- 

 ment produced subsequently by the outlet of the glacial Lake Maumee 

 has, to a great degree, effaced the terraces or other evidences of glacial 

 discharge which may have been formed. In the city of Wabash, however, 

 tliere is a terrace on which the court-house stands whose altitude is about 

 70 feet above the river, and this niay be of the age of the Mississinawa 

 moraine. It appears to be the upper terrace at that point. There is a rock 

 shelf capped by a coating of gravel and cobble such as commonly charac- 

 terizes the glacial terraces, but little earthy material being intermixed. The 

 rock platform referred to appears to be the top of an old rock bluff, no rock 

 of higher altitude having been noted in the bluff or border of the terrace 

 north of the river. The shelf here produced is to all appearance excavated 

 from drift material only, and does not represent the amount of work that 

 would have been involved had it been excavated in the rock. From its 

 b(irder there is a gentle rise to the upland, whose altitude is 50 to 75 feet 

 above the terrace. 



