A sufficient number of sacrificial mounds has been opened to justify the adoption of certain general conclusions relative to their construction and the purposes for which they were designed. On the natural surface of the ground, in most cases, a basin of fine clay appears to have been modelled with care, in a perfectly symmetrical form, but varying in shape, and still more in dimensions. They have been found square, round, elliptical, and in the form of parallelograms; and, in size, range from a diameter of two feet, to fifty or sixty feet long, and twelve or fifteen feet wide. The most common dimensions, however, are from five to eight feet in diameter. The clay basin, or “altar,” as it has been designated, invariably exhibits traces of having been subjected to the action of fire, and frequently of intense and long-continued or oft-repeated heat. It is, moreover, evident that in some cases it had not only been often used; but, after being destroyed by repeated exposures to intense heat, it had been several times remodelled before it was finally covered over by the superincumbent mound. Within the focus or basin of the altars are found numerous relics: elaborate carvings in stone, ornaments cut in mica, copper implements, disks, and tubes, pearl, shell, and silver beads, and various other objects, hereafter referred to, but all more or less injured by fire. In some cases the carved pipes and other works in stone have been split and calcined by the heat, and the copper relics have been melted, so that the metal lies fused in shapeless masses in the centre of the basin. Traces of cloth completely carbonised, but still retaining the structure of the doubled and twisted thread; ivory or bone needles, and other objects destructible by fire, have also been observed; and the whole are invariably found intermixed with a quantity of ashes. Large accumulations of calcined bones, including fragments of human bones, also lay above some of the deposits, or mingled with them; and in other cases a mass of calcined shells, or of fine carbonaceous dust, like that formed by the burning of vegetable matter, filled up the entire hollow. But while it is obvious from a few traces, that the deposits on the altars had included offerings of objects which yielded at once to the destructive element to which they were there exposed, as well as others capable in some degree of withstanding the intensity of the flame: there are only faint traces of all but the least destructible relics of stone or metal. In one mound portions of the contents were cemented together by a tufa-like substance of a grey colour, resembling the scoriæ of a furnace, and of great hardness. But subsequent analyses demonstrated that it was made up in part of phosphates; and a single fragment of partially calcined bone found on the altar was the patella of a human skeleton. The long-continued, and probably oft-repeated application of intense heat had reduced the cemented mass to this condition.