Assuming that these post-glacial gravels about Trenton supply one of the earliest authentic starting points in the history of culture on this continent, the later developments of industry will furnish a number of other data. This first date was long before the extinction of the native American horse, the elephant, the mammoth, and other animals important to early man. There is nothing unlikely therefore in the reported discoveries of his pointed flints or his bones in place along with the remains of these quadrupeds. Not only the form but the material of implements supplies us data. If man in his earliest stage was, as some maintain, quite migratory, it is certain that he did not carry his stone implements with him, nor did he obtain by barter or capture those of other tribes. All the oldest implements are manufactured from the rocks of the locality. When, therefore, we find a weapon of a material not obtainable in the vicinity, we have a sure indication that it belongs to a period of development considerably later than the earliest. When the obsidian of the Yellowstone Park is found in Ohio, when the black slate of Vancouver’s Island is exhumed in Delaware, it is obvious we must assume for such extensive transits a very noticeable æsthetic and commercial development. I can but touch in the lightest manner on the data offered by the vast realm of industrial activity. The return it offers is abundant, but the harvesting delicate. In the dissemination of certain kinds of arts, certain inventions, certain decorative designs and æsthetic conceptions from one tribe to another, we have a most valuable means of tracing the pre-historic intercourse of nations: but we must sedulously discriminate such borrowing from the synchronous and similar development of independent culture under like conditions.