SOCIETY OF THE UNIVERSITY OF ABERDEEN. 47 



This race must have had commercial intercourse with the natives 

 of distant regions, for amongst the articles unearthed some are made 

 of native copper from Lake Superior, and there are also found mica 

 from the Alleghanies, and sea shells from the Gulf of Mexico. 



The extraordinary number of these mounds implies a long period 

 during which a settled agricultural population had made considerable 

 progress in civilisation. The mounds are almost all confined to fertile 

 valleys, and some at least are so ancient that rivers have had time 

 to encroach on the lower terraces which support them, and again to 

 recede for the distance of nearly a mile after having undermined a 

 part of the works. The only data as yet obtained for calculating the 

 probable time since these mounds have been abandoned have been 

 derived from the age and nature of the trees found growing on them. 

 One of these has, when cut down, displayed no less than 800 rings 

 of annual growth, and Harrison, a late President of the United States, 

 who was well skilled in woodcraft, has remarked in a paper on this 

 subject that several generations of trees must have lived and died 

 before the mounds could have been overspread with that variety of 

 species which they supported when the white man first beheld them. 



A somewhat similar mound in Brazil was visited by Sir Charles 

 Lyell, in which was found a large number of human skeletons regu- 

 larly arranged from east to west and embedded in solid rock. This 

 mound, about 3 acres in extent and 14 feet in height, was covered 

 with trees. It had been undermined by the river Santos, thus 

 exposing the skeletons to view. The presence of oysters and other 

 sea shells in the mound led Sir Charles at first to suppose that 

 it had been submerged under the sea and again upheaved, but he 

 afterwards came to the conclusion that the shells had been brought 

 there and heaped up with other materials when the bodies were 

 buried, and that subsequently the whole artificial earthwork may have 

 become infiltrated with carbonate of lime, and the mound may there- 

 fore be of no greater antiquity than those on the Ohio. 



We will now return home and notice the occurrence of canoes 

 from time to time brought to light in works of excavation on the 



