via THE ANTIQUITY OF MAN IN NORTH AMERICA 435 



as well as from trained observers who are fully aware of the 

 importance of every additional fact and the weight of each 

 fresh scrap of evidence. Having by the kindness of Major 

 Powell, the able Director of the United States Geological Sur- 

 vey, been able to look into the evidence recently obtained 

 bearing on this question in the North American continent, I 

 believe that a condensed account of it will certainly prove of 

 interest to English readers. 



The most certain tests of great antiquity, even though they 

 afford us no accurate scale of measurement, are furnished by 

 such natural changes as we know occur very slowly. Changes 

 in the distribution of animals or plants, modifications of the 

 earth's surface, the extinction of some species and the intro- 

 duction of others, are of this nature, and they are the more 

 valuable because during the entire historical period changes 

 of this character are either totally unknown or of very small 

 amount. Let us then see what changes of this kind have 

 occurred since man inhabited the North American continent. 



Ancient Shell Mounds 



The shell heaps of the Damariscotta River, in Maine, are re- 

 markable for their number and extent. The largest of these 

 stretches for about half a mile along the shore, and is often six 

 or seven feet, and in one place twenty-five feet, in thickness. 

 They consist almost exclusively of oyster shells of remarkable 

 size, frequently having a length of eight or ten inches, and some- 

 times reaching twelve or fourteen inches. They contain frag- 

 ments of bones of edible animals, charcoal, bone implements, and 

 some fragments of pottery. The surface is covered to a depth 

 of several inches with vegetable mould, and large trees grow on 

 them, some more than a century old. The special feature to 

 which we now call attention is "that at the present time 

 oysters are only found in very small numbers, too small to 

 make it an object to gather them ; and we were credibly in- 

 formed that they have not been found in larger quantities 

 since the settlement in the neighbourhood. It cannot be sup- 

 posed that the immense accumulations now seen on the shores 

 of Salt Bay could have been made unless oysters had existed 

 in very large numbers in the adjoining waters." x Here we 

 1 Second Annual Report of Trustees of Peabody Museum, p. 18. 



