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: ist. 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 Hrie 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. 
