Proceeding still further southwards, we find, in the States bordering on the Gulf of Mexico, the mounds increasing in size and regularity of form, if not in numbers. Conical mounds become comparatively rare, and the Teocalli-shaped structures become larger and more numerous, and assume certain dependencies in respect to each other, not before observed. The enclosures, on the other hand, diminish in size and numbers; and lose many of the characteristic features of those of a higher latitude, though still sustaining towards them a strong general resemblance. Here, for the first time, we find traces of bricks in the mounds and in the walls of enclosures.

The peculiarities of these several divisions will be more particularly pointed out in the progress of this work; when the points of resemblance and difference will become more apparent. The succeeding observations relate more especially to the remains included in the central geographical section above indicated, where the investigations recorded in this volume were principally carried on, and which, in the extent, variety, and interesting nature of its ancient monuments, affords by far the richest and most important field for archæological research and inquiry.

The number of these ancient remains is well calculated to excite surprise, and has been adduced in support of the hypothesis that they are most, if not all of them, natural formations, “the results of diluvial action,” modified perhaps in some instances, but never erected by man. Of course no such suggestion was ever made by individuals who had enjoyed the opportunity of seeing and investigating them. Simple structures of earth could not possibly bear more palpable evidences of an artificial origin, than do most of the western monuments. The evidences in support of this assertion, derived from the form, structure, position, and contents of these remains, will sufficiently appear in the progress of this work.

Not far from one hundred enclosures of various sizes, and five hundred mounds, are found in Ross county, Ohio. The number of tumuli in the State may be safely estimated at ten thousand, and the number of enclosures at one thousand or fifteen hundred. Many of them are small, but cannot be omitted in an enumeration. They are scarcely less numerous on the Kenhawas in Virginia, than on the Scioto and Miamis; and are abundant on the White river and Wabash, as also upon the Kentucky, Cumberland, Tennessee, and the numerous other tributaries of the Ohio and Mississippi.

Nor is their magnitude less a matter of remark than their great number. Lines of embankment, varying in height from five to thirty feet, and enclosing areas of from one to fifty acres, are common; while enclosures of one or two hundred acres area are far from infrequent. Occasional works are found enclosing as many as p005 four hundred acres.[3] The magnitude of the area enclosed is not, however, always a correct index of the amount of labor expended in the erection of these works. A fortified hill in Highland county, Ohio, has one mile and five-eighths of heavy embankment; yet it encloses an area of only about forty acres. A similar work on the Little Miami river, in Warren county, Ohio, has upwards of four miles of embankment, yet encloses little more than one hundred acres. The group of works at the mouth of the Scioto river has an aggregate of at least twenty miles of embankment; yet the entire amount of land embraced within the walls does not probably much exceed two hundred acres.

The mounds are of all dimensions, from those of but a few feet in height and a few yards in diameter, to those which, like the celebrated structure at the mouth of Grave Creek in Virginia, rise to the height of seventy feet, and measure one thousand feet in circumference at the base. The great mound in the vicinity of Miamisburgh, Montgomery county, Ohio, is sixty-eight feet in perpendicular height, and eight hundred and fifty-two in circumference at the base, containing 311,353 cubic feet.