The nations that celebrated their mysteries around these mounds have long since departed; the altar fires long since burned low. We are not sure that we understand their purport, but we are certain they were regarded as of great importance, and we can readily imagine that when the fires were lit on the altars, gathering crowds stood round, and participated in the religious observance, throwing into the fire their most valued ornaments, in this manner paying their last respects to the departed chiefs and great men of their tribe.
The true burial mounds are very numerous, an comprise by far the larger number of mounds. They are to be found all over the Mound Builders’ territory, and are about the only class of remains found in the prairie regions of the West. From the upper waters of the Missouri and the great lakes on the north to the Gulf States on the south, and from west of the Mississippi to the Alleghenies of the East, in all this vast region they are the prevailing class of remains, and occur by hundreds, and even thousands, along the valleys. The mounds themselves are often not very conspicuous; as a rule they are simply heaps of dirt raised above the surface and rounded over, and from two or three to fifteen or twenty feet high, although many are of much larger size. They are seldom found on the lower, or recent river terrace, but are common on the upper terrace, and are often built upon the high bluffs bordering the streams, where a wide stretch of country is exposed to view. Black-bird, an Omaha chief, who died about the year 1800, desired to be buried on a high bluff overlooking the Missouri, so that he might see the boats passing up and down the river. Perhaps from a similar superstitious wish the Mound Builders sometimes chose the sites of their burial mounds where they could watch over their country; or it may be that the monuments over the dead were placed in such conspicuous positions that they might be readily seen by the people.
The next cut represents an ordinary burial mound, which was explored by tunneling in from one side. We notice there are no different layers or stratifications in this case. In some cases, at least, the building of such a mound occupied several years. We can see where the dirt was thrown down in small quantities, averaging about a peck, as if from a basket. In one case grass had started to grow on the unfinished surface of the mound, to be covered up by fresh dirt.24