152 Bulletin of Laboritories of Dcnison University. Vol. Xlll] 



the maximum development of the ice which deposited this drift, 

 then a lake may have existed here, but its area must have been 

 greater than has been supposed.' In discussing the silts found in 

 Ohio, Leverett says : That this region had an unfavorable altitude 

 for drainage in the preceding Sangamon interglacial stage, and 

 probably stood much lower than at present, seems evident from the 

 shallowness of the valleys which were opened on the surface of 

 the Illinoian drift. The drainage conditions seem to have be- 

 come still more unfavorable during the silt deposition, so that 

 erosion was either suspended or became so weak that it could not 

 keep pace with deposition. This increased imperfection of drain- 

 age conditions seems best explained by a depression of the land.'' 



Assuming that this depression was well in progress when the 

 Illinoian ice commenced to wane, it is possible then, with the ice 

 front at halt 5 (Fig. 3), the depression of thedand rot attain-ng 

 its maximum during this halt, that, as the level of the water 

 gradually rose, tlie load from the ice was distributed bv this water, 

 develoi)ing the existing delta-like surfaces. Under this explana- 

 tion it follows that the silt which is common over the surface of 

 the Hanover Dam was deposited after the ice had further re- 

 treated. In any event, if connection is to be established between 

 this possible silt-producing depression of the land and the origin 

 of the Hanover Dam, no long period of time can intervene ; the 

 successive halts of the ice, after its farthest reach into Muskingum 

 County, indicate appreciable time periods ; the retreat following 

 halt 5 terminated all connection of the ice with any such explana- 

 tion of the origin of this mass of drift. It is necessary, however, 

 before admitting even the feasibility of this hypothesis to recall 

 that contemporaneously with the development of the Hanover 

 Dam other deltas should have l)een in progress of formation, evi- 

 dence of which is wanting. 



With the establishment of certain prerequisite conditions either 

 of these hypotheses is sufficient to account for this delta-like ac- 

 cunuilation. I hit this drift dam is so morainic locally in surface 



• Leverett, loc. cit., p. 2SG. 

 - Loc. cit., p. 301. 



