With these figures we may compare the dimensions of the northern mounds. The massive one near Miamisburg, Ohio, 68 feet high, has been calculated to contain 311,350 cubic feet—about half the size of the Messier Mound. At Clark’s Works, Ohio, the embankments and mounds together contain about 3,000,000 cubic feet;[84] but as the embankment is three miles long, most of this is not in the mounds themselves. Greater than any of these is the truncated pyramid at Cahokia, Illinois, which has an altitude of 90 feet and a base area of 700 by 500 feet. It is, however, doubtful whether this is wholly an artificial construction. Professor Spencer Smith has shown that the once famous “big mound” of St. Louis was largely a natural formation; and he expresses the opinion that many of the mounds in Missouri and Illinois, popularly supposed to be artificial constructions, are wholly, or in great part, of geologic origin.[85] There is apparently therefore no such great difference between the earth structures of the Chahta tribes, and those left us by the more northern mound-builders, that we need suppose for the latter any material superiority in culture over the former when first they became known to the whites; nor is there any improbability in assuming that the Mound-builders of the Ohio were in fact the progenitors of the Chahta tribes, and were driven south probably about three or four hundred years before the discovery. Such is the conviction to which the above reasoning leads us. In the course of it, I have said nothing about the condition of the arts of the Mound-builders compared with that of the early southern Indians; nor have I spoken of their supposed peculiar religious beliefs which a recent writer thinks to point to “Toltec” connections;[86] nor have I discussed the comparative craniology of the Mound-builders, upon which some very remarkable hypotheses have been erected; nor do I think it worth while to do so, for in the present state of anthropologic science, all the facts of these kinds relating to the Mound-builders which we have as yet learned, can have no appreciable weight to the investigator. [Investigations conducted since the above Essay was printed require some modifications in its statements. The researches of Professor Cyrus Thomas render it likely that the Cherokees were also Mound-builders, and that they occupied portions of Western Pennsylvania and Western Virginia less than two centuries ago. (See also my work _The Lenâpè and their Legends_, pp. 16–18. Philadelphia, 1885.) Probably the Ohio Valley Mound-builders were the ancestors of some of the Cherokees as well as of the Chahta-Muskoki tribes. Craniologic data from the Ohio mounds are still too vague to permit inferences from them.] THE TOLTECS AND THEIR FABULOUS EMPIRE.