Art. V] Carney, Glacial Dam at Hanover. 151 



these waters to the valley southward ; the ice-front channels north 

 of the Brick Plant (Fig. 9) were cut during the earlier stages of 

 this halt. 



Thus the two locations that favored slack water are marked 

 by level areas ; in spots this superficial material is gravel, elsewhere 

 it resembles ordinary flood plain deposits. 



ALTERNATE HYPOTHESES. 



1. If gaps A, B and C are of post-glacial development, and 

 if there were no cross valleys to the east lower than the top of the 

 Hanover Dam, then a lake could liave occupied the valley, pro- 

 vided further that the grade of the old east-west stream had not 

 already been reversed. We feel that subaerial erosion even since 

 Kansan-drift times is incompetent to accomplish the disintegra- 

 tion represented by these north-south gaps ; only gap A ever car- 

 ried much ice-front drainage, and since the cessation of this ab- 

 normal stream work, these gaps have controlled only slight drain- 

 age basins. In view of observations which the purposes of this 

 paper do not warrant stating here the writer feels that this area 

 was tributary to eastern drainage before the earliest ice invaded 

 this part of the state.' 



Such care has been taken in mapping the area, and in the de- 

 scription of the drainage lines, that it seems needless to point out 

 the impossibility of this alternate hypothesis. It may be said in 

 addition that the great amount of aggraded ice-stream deposits 

 in the gaps B and C (Figs. G and 7), blending into the terraced 

 floodplain of the Licking indicates that, before the ice had moved 

 across or opposite their northern ends, these gaps existed in 

 greater maturity than they now indicate. Furthermore if these 

 gaps are post-glacial — even post-Wisconsin — in development, then 

 at their up-stream terminals they should open into marked flat 

 areas, since streams equal to removing the succession of rock for- 

 mations already described should have carried ofl[, incident to the 

 lateral planation activity indicated by the width of the gaps, a 

 much greater mass of glacial drift. 



2. If there was a general subsidence of the land shortlv after 



• This interpretation is contrai-y to the findings of Leverett, \of. cit., p. 15.5 ; 

 and of Tight, loc. cit., p. 47. 



