3 2o THE POPULAR SCIENCE MONTHLY. 



with no unfavorable criticism, believing that ultimately the 

 grand results of the combined labors of so many men, when 

 published, would correct all errors. 



There is another phase to this question, connected with the 

 science of archaeology. I have already set forth the distinction 

 which geologists recognize between overplacement formations and 

 fundamental formations. Certain archaeologic problems which 

 have sprung up in late years in the United States are profoundly 

 affected by the discovery and formulation of these distinctions. 

 Many years ago a local observer at Natchez, Miss., claimed to 

 have discovered a human skeleton in the loess of a bluff on the 

 Mississippi River. The loess is a formation contemporaneous 

 with the glacial formation of the North, as previously explained. 

 The discovery of a human skeleton in this situation was believed 

 to prove that man dwelt in the valley of the Mississippi during 

 the loess-forming epoch. The discovery seemed to be of so much 

 importance that the site was visited by Sir Charles Lyell, who on 

 examination at once affirmed that the skeleton was not found in 

 the loess itself, but in the overplacement or modified loess — that 

 is, in the talus of the bluff ; and all geologists and archaeologists 

 have accepted the decision. 



From time to time other supposed discoveries were * made in 

 this country ; but one after another was abandoned, until a series 

 of discoveries were made along the line of hills which stretch 

 from the Hudson to the James River. This line of hills marks 

 an interesting geological displacement. The country to the sea- 

 ward of the line has been differentially displaced from the coun- 

 try mountainward by an uplift on the Appalachian side or a 

 downthrow on the ocean side, or both. The displacement has 

 given rise to many rapids and falls in the streams. Above this 

 line of displacement the waters are not navigable, the declivity 

 of the streams being too great ; below, tidewater always flows to 

 the foot of the hills. Now, along this line of hills, back and forth 

 from the upper country to the lower, are many glacial gravels, 

 many hills of ancient river gravels, and many hills of estuarine 

 gravels, all of Glacial age. But there are other gravels of still 

 greater age intimately associated with them, and in making the 

 geological survey of the country it became necessary to distin- 

 guish the older gravels of Neocene and Cretaceous age from the 

 younger gravels of the Ice period, and it also became necessary 

 to distinguish the overplacement of modern times. In these same 

 gravels certain archaeologists had discovered what they believed 

 to be palaeolithic implements ; and as some of the gravels were 

 known to be of Glacial age, they supposed them all to be Glacial, 

 and that they thus had evidence that man inhabited the coun- 

 try during the Glacial epoch. These implements were gathered 



