CHAP. III. ANTIQUITY OF THE OHIO MOUNDS. 41 



roamed over it without any fixed abode, or any traditionary 

 connection with his more civilized predecessors. The only 

 positive data as yet obtained for calculating the minimum of 

 time which must have elapsed since the mounds were aban- 

 doned, has been derived from the age and nature of the 

 trees found growing on some of these earthworks. "When I 

 visited Marietta in 1842, Dr. Hildreth took me to one of 

 the mounds, and showed me where he had seen a tree grow- 

 ing on it, the trunk of which when cut down displayed eight 

 hundred rings of annual growth.* But the late General 

 Harrison, President in 1841 of the United States, who was well 

 skilled in woodcraft, has remarked, in a memoir on this sub- 

 ject, that several generations of trees must have lived and 

 died bcfoi'e the mounds could have been overspread with 

 that variety of species which they supported when the white 

 man first beheld them, for the number and kinds of trees 

 were precisely the same as those which distinguished the 

 surrounding forest. '^We may be sure," observed Harrison, 

 "that no trees were allowed to grow so long as the earthworks 

 were in use ; and when they were forsaken, the ground, like all 

 newly cleared land in Ohio, would for a time be monopolized 

 by one or two species of tree, such as the yellow locust and 

 the black or white walnut. When the individuals which were 

 the first to get possession of the ground had died out one 

 after the other, they w^ould in many cases, instead of being 

 replaced by the same species, be succeeded (by virtue of the 

 law which makes a rotation of crops profitable in agriculture) 

 by other kinds, till at last, after a great number of centuries 

 (several thousand years, perhaps), that remarkable diversity 

 of species characteristic of North America, and far exceeding 

 what is seen in European forests, would be established." 



* Lyell's Travels in North America, vol. ii. p. 29, 



