232 ANCIENT EARTHWORKS OF OHIO. 



and sometimes have imitative forms, as that of birds, lizards, bears 

 and panthers,* cames perfect conviction to the minds of persons 

 most familiar with them, that they ai'e the result of human zeal 

 and perseverance. The most'common form is either an isolated 

 circular tumulus, from the lowest perceptible, to those which are 

 ninety feet in altitude, or long lines of embankment often enclo- 

 sing an area of from one acre to several hundix'd acres. In some 

 places these embankments approach nearly to some mathematical 

 figure, as a square, a circle, or an ellipse ; in others again, their 

 form has been determined by the shape of the gi'ound, especially 

 where the work occupies the top of a terrace, when it follows the 

 highest crest or verge of the declivity along the edge of the sm-- 

 rounding ravine. But my object is not so much to describe these 

 works, as to make use of them as geological monuments by which 

 to determine some facts with regard to recent surface action. 



The degree of antiquity of these works, a problem of vast in- 

 terest, has not yet been determined. We have however data for 

 a negative solution to some extent, as we have in reference to the 

 distance of the fixed stars, the want of parallax of which shows 

 them to be beyond a very remote limit. It wdll be seen by refer- 

 ence to the second Ohio Report, p. 269, that on the embankment 

 of a work in Highland county, Ohio, ah-eady refeiTcd to, there 

 were a chestnut tree, six feet in diameter, and a tulip poplar, 

 seven feet in diameter, the former having six hundred, and the 

 latter, six hundred and seven annual grains of growth. As it 

 would probably be several years after the commencement of these 

 works before their completion, and several years more before any 

 trees would be permitted to grow upon them, I estimated their 

 origin to have been at least one thousand years anterior to the 

 time of my examination. General Harrison, in his late address 

 on the subject of the Aborigines, by the following reasoning, 

 extends the period much fm'ther. He states, on the authority of 

 his own observations in the West, that when the forest trees have 

 been once cleared from the ground, and a new gi-owth shall have 



* See Mr. Taylor's account of the " Animal EfRgries " of Wisconsin, published in Prof. 

 Silliman's Journal. Having examined the same locality, and re-surveyed the same works, 

 I am happy to add my testimony to the faithfulness of that gentleman's descriptions. 



