Page:Popular Science Monthly Volume 43.djvu/334

320 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 archæology. I have already set forth the distinction which geologists recognize between overplacement formations and fundamental formations. Certain archæologic 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 archæologists 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 seaward of the line has been differentially displaced from the country 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 distinguish 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 palæolithic 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 country during the Glacial epoch. These implements were gathered