In the mounds we find many works of copper but none of bronze. This may indicate one of two things: either the colonies which settled the Mississippi Valley may have left Atlantis prior to the discovery of the art of manufacturing bronze, by mixing one part of tin with nine parts of copper, or, which is more probable, the manufactures of the Mound Builders may have been made on the spot; and as they had no tin within their territory they used copper alone, except, it may be, for such tools as were needed to carve stone, and these, perhaps, were hardened with tin. It is known that the Mexicans possessed the art of manufacturing true bronze; and the intercourse which evidently existed between Mexico and the Mississippi Valley, as proved by the presence of implements of obsidian in the mounds of Ohio, renders it probable that the same commerce which brought them obsidian brought them also small quantities of tin, or tin-hardened copper implements necessary for their sculptures. The proofs, then, of the connection of the Mound Builders with Atlantis are: 1. Their race identity with the nations of Central America who possessed Flood legends, and whose traditions all point to an eastern, over-sea origin; while the many evidences of their race identity with the ancient Peruvians indicate that they were part of one great movement of the human race, extending from the Andes to Lake Superior, and, as I believe, from Atlantis to India. 2. The similarity of their civilization, and their works of stone and bronze, with the civilization of the Bronze Age in Europe. 3. The presence of great truncated mounds, kindred to the pyramids of Central America, Mexico, Egypt, and India. 4. The representation of tropical animals, which point to an intercourse with the regions around the Gulf of Mexico, where the Atlanteans were colonized. 5. The fact that the settlements of the Mound Builders were confined to the valley of the Mississippi, and were apparently densest at those points where a population advancing up that, stream would first reach high, healthy, and fertile lands. 6. The hostile nations which attacked them came from the north; and when the Mound Builders could no longer hold the country, or when Atlantis sank in the sea, they retreated in the direction whence they came, and fell back upon their kindred races in Central America, as the Roman troops in Gaul and Britain drew southward upon the destruction of Rome. 7. The Natchez Indians, who are supposed to have descended from the Mound Builders, kept a perpetual fire burning before an altar, watched by old men who were a sort of priesthood, as in Europe.