With regard to the first era, it is almost wholly the subject of general and profound scientific and philosophical investigations, which require a union of great advantages for successful study. The second and third eras, fall within the compass of ordinary observation. Both kinds of proof may exist at the very same localities. They do not necessarily imply diverse or remote geographical positions. We know that some of the leading tribes, the Cherokees, (till within a few years,) and the Iroquois, for instance, have continued to live in the very same positions in which they were found by the first explorers. As their chiefs and warriors died, they carried to their places of burial, (such was the result of ancient and general custom,) those kinds of ornaments, arms and utensils, which were the distinguishing tokens of art, of the several eras in which they lived. The coming of European races among them introduced fabrics of metal, earths, enamels, glass, and other materials more or less durable, and capable of resisting decomposition. These would necessarily take the place of the aboriginal articles of stone and shell, before employed. If, then, places of sepulture were permanent, the inquirer at the present day would find the various fabrics of the second and the third era, in the same cemeteries and burial grounds, and sometimes in the same barrows and mounds. Modes of defence would also alter by the introduction of the second period. The simple ring-fort, with palisades, crowning a hill, which would serve as a place of excellent defence, against bows and arrows and clubs, would prove utterly useless, as the Tuscaroras found at Naharuke in 1712, after the introduction of artillery. A trench to obtain water, from a spring or creek, leading from one of the works of the older period, might have been so covered as to afford full protection from the simple aboriginal missiles. Besides this, the combination of several tribes, as the Iroquois, the Algonquins, the Eries, Alleghans and others, might render these simple forts, defended with ditches, mounds, and otherwise, no longer necessary, in the interior of their territory, after the time of such general combinations or confederacies. And in this case, these works would be deserted and become ruins, long before the period of the discovery.