98 INTRODUCTION. 



of men, moving in the same general direction, acting undti common 

 impulses, and influenced by similar causes. 



He thinks the present condition of our knowledge on this subject 

 indicates a connection between the builders of the mounds and the 

 half-civilized nations of Mexico, Central America, and Peru, whose 

 vast and imposing structures invest this part of the continent " with 

 an interest not less absorbing than that which attaches to the valley 

 of the Nile." The mound builders, like the last-mentioned nations, 

 were, to a considerable extent, stationary and agricultural in their 

 habits, — "conditions indispensable to large population, to fixedness 

 of institutions, and lo any considerable advance in the economical or 

 ennobling aits." 



While it is impossible to fix accurately the date of the ancient 

 monuments, many facts enable us to judge approximately. None of 

 these monuments occur upon the latest-formed terraces of the river 

 valleys of Ohio. We are warranted in believing that these terraces 

 mark the degrees of subsidence of the rivers, and one of the four 

 which can now be traced must have been formed since these rivers 

 have followed their present courses. " There is no good reason for 

 supposing that the mound builders would have avoided building upon 

 that terrace, while they erected their works promiscuously upon all 

 the others." lie adds, " The time since the streams have flowed in 

 their present courses may be divided into four periods, of different 

 lengths, of which the latest, supposed to have elapsed since the race 

 of the mounds flourished, is much the longest." 



The primitive forests which cover these mounds are in no way 

 distinguishable from those which surround them. Some of the 

 trees of these forests have a positive antiquity of 6 or 800 years. 

 The process by which nature restores the forest to its original state, 

 after being once cleared, is extremely slow. Without attempting 

 to assign a definite period for such an assimilation, he says, " it 

 must, unquestionably, however, be measured by centuries." 



S. K. 



Boston, 1851. 



