It would be difficult to explain the existence of accumulations of this kind if we did not know from the accounts of ancient authors that the Indians were in the habit of assembling every eight or ten years in some appointed spot to inter all together in one mass the bones of their dead friends, which had been previously exhumed. This singular ceremony was called "the feast of the dead."
We shall not say much here as to the sacrificial mounds, because no very precise agreement has yet been arrived at as to their exact signification. Their chief characteristics are, that, in the first place, they are nearly always found within certain sacred enclosures of which we shall have more to say further on, and also that they cover a sort of altar placed on the surface of the ground, and made of stone or baked clay. In the opinion of certain archæologists, this supposed altar is nothing but the site of a former fire-hearth, and the mound itself a habitation converted into a tomb after the death of its proprietor. It will therefore be best to reserve our judgment as to the existence of the human sacrifices of which these places might have been the scene, until we obtain some more complete knowledge of the matter.
The Temple-Mounds are hillocks in the shape of a truncated pyramid, with paths or steps leading to the summit, and sometimes with terraces at different heights. They invariably terminate in a platform of varying extent, but sometimes reaching very considerable dimensions. That of Cahokia, in Illinois, is about 100 feet in height, and at the base is 700 feet long and 500 feet wide. There is no doubt that these mounds were not exclusively used as temples, and, adopting as our authority several instances taken from Indian history, we may be permitted to think that on this upper terrace they were in the habit of building the dwelling of their chief.
The most curious of these earthworks are, beyond question, those which the American archæologists have designated by the name of animal-mounds. They consist of gigantic bas-reliefs formed on the surface of the ground, and representing men, mammals, birds, reptiles, and even inanimate objects, such as crosses, pipes, &c. They exist in thousands in Wisconsin, being chiefly found between the Mississippi and Lake Michigan, and along the war-path of the Indians. Their height is never very considerable, and it is but seldom that they reach so much as 6 feet; but their length and breadth is sometimes enormously developed. Many of these figures are copied very exactly from Nature; but there are, on the other hand, some the meaning of which it is very difficult to discover, because they have been injured by the influence of atmospheric action during a long course of ages.
In Dale county there is an interesting group composed of a man with extended arms, six quadrupeds, a simple tumulus, and seven mounds without any artistic pretensions. The man measured 125 feet long, and nearly 140 feet from the end of one arm to the other. The quadrupeds are from 100 to 120 feet long.
The representation of lizards and tortoises are frequently recognised in these monstrous figures. A group of mounds, situate near the village of Pewaukee, included when it was discovered two lizards and seven tortoises. One of these tortoises measured 470 feet. At Waukesha there was found a monstrous "turtle" admirably executed, the tail of which stretched over an extent of 250 feet.
On a high hill near Granville, in the state of Ohio, a representation is sculptured of the reptile which is now known under the name of alligator. Its paws are 40 feet long, and its total length exceeds 250 feet. In the same state there exists the figure of a vast serpent, the most remarkable work of its kind; its head occupies the summit of a hill, round which the body extends for about 800 feet, forming graceful coils and undulations; the mouth is opened wide, as if the monster was swallowing its prey. The prey is represented by an oval-shaped mass of earth, part of which lies in the creature's jaws. This mass of earth is about 160 feet long and 80 feet wide, and its height is about 4 feet. In some localities excavations are substituted for these raised figures; that is to say, that the delineations of the animals are sunk instead of being in relief-a strange variety in these strange works.
The mind may readily be perplexed when endeavouring to trace out the origin and purpose of works of this kind. They do not, in a general way, contain any human remains, and consequently could not have been intended to be used as sepulchres. Up to the present time, therefore, the circumstances which have accompanied the construction of these eminently remarkable pre-historic monuments are veiled in the darkest mystery.
We now have to speak of those enclosures which are divided by American archæologists into the classes of defensive and sacred. This distinction is, however, based on very uncertain data, and it is probable that a large portion of the so-called sacred enclosures were in the first place constructed for a simply defensive purpose. They were, in general, composed of a wall made of stones, and an internal or external ditch. They often assumed the form of a parallelogram, and even of a perfect square or circle, from which it has been inferred that the ancient Indians must have possessed an unit of measurement, and some means of determining angles. These walls sometimes embraced a considerable area, and not unfrequently inside the principal enclosure there were other smaller enclosures, flanked with defensive mounds performing the service of bastions. In some cases enclosures of different shapes are grouped side by side, either joined by avenues or entirely independent of one another.
The most important of these groups is that at Newark, in the Valley of Scioto; it covers an area of 4 square miles, and is composed of an octagon, a square, and two large circles. The external wall of one of these circles is even at the present day 50 feet in width at the base, and 13 feet high; there are several doorways in it, near which the height of the wall is increased about 3 feet. Inside there is a ditch 6 feet in depth, and 13 feet in the vicinity of the doors, its width being about 40 feet. The whole enclosure is now covered by gigantic trees, perhaps 500 or 600 years old—a fact which points to a considerable antiquity for the date of its construction.