The peculiar feature, however, is the altar at the bottom of the mound, directly above the natural surface of the ground. The small cut gives us a clear idea of the altar, the light lines running around it showing the plan. These altars are almost always composed of clay, though some of stone have been discovered. They are of various shapes and sizes. We notice the dish-shaped depression on the top of the altar. The clay of which they are composed seems to have been moulded into shape directly over the surface of the ground. Sometimes a layer of sand was put down as a foundation. They are nearly always thoroughly burned, the clay being baked hard, sometimes to the depth of fifteen or twenty inches. This must have required intense and long continued heat. We are at once curious to know the object of this altar. Within the basin-shaped depression are generally found all manner of remains. Sometimes portions of bones, or fragments of wood, arranged in regular order; pieces of pottery vessels, and implements of copper and stone; spear-heads, arrow-heads, and fragments of quartz and crystals of garnet. Pipes are a common find, carved in miniature figures of animals, birds, and reptiles. Two altar-mounds but recently examined near Cincinnati had altars about four feet square that were loaded down with ornaments. One especially contained quantities of ornaments of stone, copper, mica, shells, the canine-teeth of bears and other animals, and thousands of pearls. They were nearly all perforated, as if for suspension. Several of the copper ornaments were covered with native silver which had been hammered out into thin sheets and folded over the copper. One small copper pendant seems to have been covered with a thin sheet of hammered gold, as a small piece was still clinging to it. This is the first example of finding native gold in the mounds.19 On this altar were also found masses of meteoric iron, and ornaments of the same material. One piece of mica showed the profile of a face.20 In all cases the articles found on the altars show the action of fire. We seem justified, then, in supposing that after the altar was formed, fires were lit on them, and into this fire were thrown the various articles just enumerated. But what was all this for? This will probably never be very clear to us, beyond the fact that it was a religious rite. Portions of the human skeleton have been found on these altars, and it has been suggested that human victims were at times part of the sacrifice; but as it is known that this people practised cremation, it may be that the altars were sometimes used for that purpose, the remains being afterwards gathered and buried elsewhere.