4 GEOLOGY OF OHIO. 



man's presence in the valley of the Ohio and its tributaries will reward 

 the patient investigator. The series of gravel beds in the two regions 

 are practically of the same age, belonging to the period immediately fol- 

 lowing the recession of the ice-sheet after it had reached its southernmost 

 limit, and were deposited by the great floods resulting from the 

 melting ice. 



If it can be proven that these implements are scattered promiscu- 

 ously throughout gravel which has remained as it was originally deposited, 

 the fact of human existence during or at the close of the glacial period is 

 beyond controversy. 



Implements have been found in several places in Ohio under such 

 conditions that the time of their manufacture would appear certainly to 

 have preceded that in which the river valleys were filled with the drift; 

 notably the, chipped flint found at Madisonville by Dr. Metz twelve feet 

 beneath the surface in a knoll higher than any other ground within 

 several hundred yards. On the other hand, specimens from Piqua, which 

 were reported to occur under conditions essentially similar to the last, 

 and which much resemble some of the European implements from the 

 drift, have been found, as was afterward determined, intermingled with 

 ordinary Indian relics, under flood deposits which may have accumulated 

 within a few decades. 



The streams in the glaciated district of Ohio have worn their beds 

 from the level of the highest terraces bordering them, to that at which 

 they are now found; this erosion was more rapid in former time than at 

 present. The shifting of such streams from side to side of the alluvial 

 lands through which they flow is also quite rapid in some cases; it being 

 not unusual for a river or creek to change its course hundreds of yards 

 in a single generation, cutting away the earth on one side and filling it 

 in at a lower level on the other. With a rapid current to carry away the 

 detritus, a stream will in this manner often produce a vertical bank to the 

 top of any terrace against which it may impinge; and when it again 

 makes its way toward the opposite side of the valley, denudation will 

 give to this bank a slope whose inclination will depend upon the character 

 of the material and the length of time given to atmospheric agencies for 

 their action. These alterations have been continually in progress since 

 drainage was established along its present lines. For this reason, a stone 

 implement of any description that was once on top of the ground, or in 

 the soil near the top, may now be found in clean gravel much below the 

 present surface, some distance from a stream or at a considerable eleva- 

 tion above it, or may be covered by a mass of earth nearly equal to the 

 thickness of the highest gravel bank reached by the water; — and yet 

 have come to its present position within a few centuries; for polished 

 grooved axes and well finished spear-heads have been found at a depth 

 of twelve feet or more in river bottoms. The discovery of an implement, 

 no matter how rudely finished, under such circumstances is by no means 



