1 66 Bulletin of Laboratories of Dcnison Uni7'('rsity. Vol. XllI] 



no glacial debris on this end. Its absence can readily be ex- 

 plained by the presence of such a stream which, turning- the bend 

 eastward on emerging from Spring Valley, would first be checked 

 in its speed, leaving a large part of its load behind, then with 

 renewed force would sweep along between the northern end of the 

 east valley wall and the ice, clearing from the former any debris 

 which may have been laid before .the genesis of this stream. 



Part of this debris would be carried forward with the stream, 

 part dropped to its bottom, this process continuing as the stream 

 lowered itself between the rock wall and the ice. As the Raccoon 

 ice tongue retreated back of this valley end, this stream would be 

 finally released so that a normal route could be followed from 

 Spring Valley to the drainage line of Raccoon \"alley. Any ter- 

 race left would be rapidly obliterated by weathering and erosion, 

 though even now the lower slope of this end wall is suggestive of 

 a former stream terrace. 



SUMMARY. 



A. That the Spring \'alley stream is not of pre-glacial origin is 



proved by 



1. Its position on the east rock wall of the Old A'alley, fol- 



lowing a lateral course parallel to the axis of this Old 

 Valley. 



2. The fact that its triluitaries formerly emptied into the 



drainage line of the Old Valley. 



3. The character of its rock walls and of the glacial debris 



found along its course. 



B. That Spring A'alley is of late glacial origin, having started 



between the margin of the ice and the valley wall, is sup- 

 ported by 



1. The elimination as not plausible of a pre-, post-, and early 



glacial genesis. 



2. By the strict accordance of this theory with the possibili- 



ties. 



C. Theory and data suggest that the Spring Valley stream con- 



tinued around the north end of the east wall of the Old 

 A^alley between ice and rock until the retreat of the 

 Raccoon ice-tongue. 

 Geological Department, Deiiison University, Granville, Ohio, 

 July, 1907. 



