32 GEOLOGY OF OHIO. 



17. Grand Sable, south shore of Lake Superior. Layer of roots and limbs 

 of trees, sometimes 12 or 14 feet thick, resting on bluish-drab clay, cov- 

 ered with sand interstratified with gravel 300 feet thick. (Sir William 

 Logan, Geology of Canada, 1863, p. 905.) 



18. Toronto, Canada. Trunks and branches of trees imbedded in yel- 

 low clay overlying blue clay, at a depth of from 10 to 20 feet from the sur- 

 face. (Prof. Hinds.) 



It is by no means certain that all the cases cited above belong to one 

 category, as timber may have been buried, in some instances, quite 

 deeply, by causes that now are in operation ; but excluding all doubtful 

 cases, a sufficient number of well authenticated facts remain to justify 

 us in the conclusion announced on a preceding page, viz: 1st. That 

 after the retreat of the glacier from the glaciated area, a growth of veg- 

 etation spread over the surface of the bowlder clay, reaching northward 

 to and into the lake-basin, and westward to and beyond the Mississippi. 

 2d. That a forest occupied the surface long enough to produce a deep car- 

 bonaceous soil over all the lower and more moist portions. 3d. In the 

 marshy portions of this land surface beds of peat were formed, in some 

 instances even 20 feet in thickness. 4th. Most of the ancient forest was 

 coniferous, and cedar and cranberry grew in the peat bogs ; from which 

 we may infer that the climate was colder than now in the same region. 

 5th,. In the Forest Bed we find the remains of the mammoth, mastodon, 

 giant beaver,* and some other animals, which mark this as the first 

 horizon of life in the Drift series. In deposits of later age, even reach- 

 ing to the advent of man, extinct or existing species of animals and 

 plants are abundantly represented, but I have never been able to obtain 

 any proof of the existence of organic remains in the Erie clay. 



While ice covered so much of our State, whatever animal or vegetable 

 life existed north of the Ohio was confined to the highlands east of the 

 Scioto valley. We have every reason to believe, however, that the mam- 

 moth, mastodon, megatherium, megalonyx, etc., lived on the southern 

 portion of our continent during the glacial period. 



Though occupying an insignificant portion of the vertical thickness of 



* In several of the wells which penetrate the Forest Bed, chopped timber and chips 

 are reported to have been found. As the number of such cases is so numerous, we 

 must suppose that the stories are founded on fact, and I have suggested that possibly 

 the chopping was done by the great dental chisels of the giant beaver. The common 

 beaver is capable of cutting down trees of large size, as at one of our camps on the 

 Dolores river, in Arizona, I measured three cottonwood trees, felled by the beaver, 

 each of which was more than two and one-half feet in diameter above the cut. The 

 Giant Beaver could as easily have felled trees six in diameter. 



