The chief relics left by this comparatively polished race are the very numerous mounds, or artificial hills, found scattered over the country. These are sometimes ten, and sometimes forty and fifty, feet in height, with widely varying bases. They present many forms; they are circular and pyramidal, square and polygonal, and in some places are manifestly imitations of the shapes of beasts, birds, and human beings. There are districts where hundreds of these mounds appear within a limited area. Sometimes--as at Aztalan, in Wisconsin, and at Newark, in the Licking Valley--a vast series of earthwork enclosures is discovered, sometimes with embankments twelve feet high and fifty broad, within which are variously shaped mounds, definitely formed avenues, and passages and ponds. These enclosures amply prove, aside from the geological evidences of their antiquity, the existence of a race very different from the Red Indians. They were clearly a people not nomadic, but with fixed settlements, cultivators of the soil, and skilful in the art of military defence. [Sidenote: Altars and Temples.] The excavations of the wonderful mounds have brought to light many things more curious than the mounds themselves. It seems to be established that the mounds were used for four distinct purposes. They were altars for sacrifice, and, like the Persians, whose sacrificial ceremonies strikingly resembled those of the Mound-Builders, they were sun-worshippers. They offered up the most costly gifts, and even human victims. The pyramidal mounds, with avenues leading to the summits, were the sites of the stately sun and moon temples. Here, undoubtedly, imposing ceremonies were often performed. The lower or "knoll" mounds were used as the sepulchres of the dead. They yield up to the modern antiquary numberless skulls, of a type distinctly different from those of the Red Indians. The Mound-Builders buried their dead, most often, in a sitting posture, adorned with shell beads and ivory ornaments. Sometimes the dead were burned. Finally, the mounds were employed as points of observation. [Sidenote: Relics of the Mounds.] [Sidenote: Early Arts.]