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.