GLACIAL SUCCESSION IN OHIO. I 33 



sections are reported to have passed through a black mucky clay, 

 probably a preglacial soil, immediately beneath the blue till and a 

 few feet above the rock surface. This feeble abrasion is thought 

 to be due to lack of vigor in the ice-movement. The attenuated 

 border is apparently due to the same lack of vigor and to a 

 comparatively short^occupancy of the region by the ice-sheet. 

 The lack of vigor in this earlier invasion is in striking contrast 

 with the vigor of the invasion which produced the outer moraine 

 of the Miami and Scioto lobes, there being numerous exposures 

 of striation in the district immediately north of that moraine, 

 while the moraine itself bears evidence that the ice-sheet had 

 great shoving power. 



There is a possibility that this earlier drift sheet embraces 

 two distinct periods of deposition. Evidence in support of this 

 -view is cited by Professor Orton in his report on Clermont 

 county, Ohio (the county bordering the Ohio river just above 

 Cincinnati), viz., that a buried soil and deposit of bog iron 

 occur at the junction between the yellow and blue tills. From 

 Professor Orton's account it would appear that no marked oxida- 

 tion of the surface of the underlying blue till had occurred 

 before the yellow till was deposited. We infer from this that 

 the interval of deglaciation may have been comparatively brief, 

 though it is possible that swampy conditions, such as prevail in 

 the production of bog iron, prevented oxidation during a pro- 

 longed period. Inasmuch as Professor Orton is a careful 

 observer and cautious writer, I do not feel free to question the 

 evidence he cites, but my examinations in this district have not 

 confirmed his evidence, so far as the location of the soil bed at this 

 particular horizon is concerned. I have found testimony as to 

 the occurrence of buried wood at or near this horizon, but not 

 of soil beds. Possibly Professor Orton considers the occur- 

 rence of wood good evidence of an old land surface, but in view 

 of the fact that wood may be incorporated in the drift as a part of 

 the glacial debris I have not thought this a sure evidence. In 

 the lists given in the Ohio reports, Dr. Newberry cites instances 

 of wood to prove the existence of a " forest bed," and forest 



