ARCHEOLOGY. 39 



ment that the country was a prairie in the time of the Mound Builders. 

 The many timber remains in mounds effectually dispel this hypothesis. 



Various earthworks have been encroached upon by streams near 

 which they were built; sometimes a river has partially cut down a mound 

 or embankment and then worked its way in the opposite direction, form- 

 ing a low timber-covered bottom of considerable width. Such a process 

 is generally supposed to require a very long period; but it may take 

 place in a short time, from the constant shifting of channels in alluvium. 

 Occasionally embankments appear to have been partially destroyed, 

 which were realty constructed as they now exist. The line B in Plate 

 III which appears to be the residue of a complete circle originally extend- 

 ing over a portion of the terrace now washed away, was built thus, to 

 reach the bank which is now where it was then. 



It is singular, though perhaps only a coincidence, that the cairns and 

 mounds between the Alleghanies and the Blue Ridge, thought to have 

 belonged to tribes which roamed over that region up to the middle of the 

 last century, yield numerous slate gorgets and steatite pipes of the forms 

 common or almost typical to the Ohio mounds, along with relics more 

 common near the sea-coast. Whether this fact, and the almost total 

 absence of grooved axes from the mounds, have any bearing on the ques- 

 tion of age, remains to be decided. 



On ground not subject to wash or overflow, the accumulation of soil 

 from the decay of vegetation, is nearly three inches in a century. Hence 

 the depth of village-sites beneath the surface offers some clue to the num- 

 ber of years since their abandonment. But there are so many disturbing 

 influences that it is unsafe to place much reliance on such measurements. 



Nothing can be judged of the age of a skeleton from its condition ; 

 the preservation of bones is dependent entirely upon the protection 

 afforded them, regardless of the length of time they have been buried. 

 If kept perfectly dry they may last thousands of years; if exposed to 

 dampness they may utterty disappear in a very short while. 



The existence in "Wisconsin of an effigy mound in the form of a 

 mammoth mastodon, and the discovery in Iowa of two pipes of the same 

 pattern, shows that their makers had some knowledge of such an animal. 

 This, also, has led many authors to attribute a very great antiquity to the 

 remains; the same geologist who has seen wood that had lain on the 

 ground in the open air for five centuries, asserts that they must neces- 

 sarily be many thousand years old. Other writers have assailed vigor- 

 ously the genuineness of the pipes and the likeness of the mound to its 



