1 62 Bulletin of Laboiafories of Dcnison University. Vol. xill] 



sponds to Leverett's description of the Illinoian drift'. At several 

 points in the cut a thin hedding' of foreign pebbles cemented into 

 a conglomerate like mass was noted. The stained and weather- 

 worn appearance of these masses suggests great antiquity. 



The compactness of all the drift lying below the recent deposit 

 of the Spring \ alley flood plain at the point mentioned implies 

 great pressure, due probably to overlying debris which has been 

 removed, and the weight oi the over-riding ice. Many large gran- 

 ite bowdders are also noted at this point and southward, the 

 presence of which will be discussed later. 



The history for the second tributary streams S' is similar to 

 that for S, but the explanation is more complicated. The more 

 northerly of the two small streams runs over rock near its junc- 

 tion with the Spring Valley stream, and shows rock walls extend- 

 ing about one foot vertical height on either side. But on the 

 north side alone can be traced the gradual rise of rock along 

 Spring Valley, representing probably the old north wall for this 

 second pre-glacial stream now tributary. Drift alone is found 

 for some distance south of this point, the other and smaller stream 

 showing no evidence of rock exposure. Presumably the first 

 stream is pursuing a course lying just at the base of the north 

 rock wall of this second valley tributary to Spring \"alley. The 

 south rock wall has not been definitely located. It is hence evi- 

 dent that these two streams have their rise in a drift-filled channel 

 tributary to the Old Valley, as in the case of the stream 5". The 

 debris-evidence in the cut of Spring \"alley stream through its 

 flood plain at this point before entering the gorge, confirms this 

 theory. 



It may be added that the flood plain material directly above the 

 rock at the points between the two tributary valleys just dis- 

 cussed, and imposed on the clay-like debris marking the old pre- 

 glacial channels of these tributaries, is itself evidence of the com- 

 paratively recent origin of Spring Valley. This ilood plain ma- 

 terial is composed of stratified layers of broken local sedimentary 

 rock mingled with glacial debris, the former generally in excess. 



THEORIES FOR ORIGIN OF SPRING YAI,LEY. 



This article has endeavored to sliow that Sirring A'alley does 



* Leverett, U. S. MoiiDjjiapli XLI, p. 27-. 



