Within the area we have thus defined are located the works of the people we call the Mound Builders. What we wish to do is to learn all about these vanished people. A great many scholars have written about them, and large collections of the remains of their handiwork have been made. There is, however, a great diversity of opinion respecting the Mound Builders and their culture. So we see we have a difficult subject to treat of. In order to gain a clear understanding of it, we must describe the remains more closely. About all we can learn of these people is from a study of their monuments. We can not call to our aid history or tradition, or rock-carved inscription, but must resort to crumbling mounds, broken down embankments; study their location, and observe their forms. To the studies in the field we must add those in the cabinet, and examine the many objects found in and above the mounds and earth-works, as well as the skeletons of the builders of the works. Rightly used, we can draw from these sources much valuable information of the people whose council-fires blazed all along the beautiful valleys of the Ohio and Mississippi rivers in times far removed from us.
We will first speak of the simplest form of these works, the ordinary conical mound. This is the one form found all over the extensive area designated. They exist in great numbers on the banks of the upper Missouri, as well as the river bottoms of the South. This cut represents a very fine specimen of a mound, in this instance surrounded by a circular embankment. We must not forget that mounds are found all over the world. “They are scattered over India, they dot the steppes of Siberia and the vast region north of the Black Sea; they line the shores of the Bosphorus and the Mediterranean; they are found in old Scandinavia, and are singularly numerous in the British Islands.”16
The principle in human nature which leads to the erection of mounds is living and active to-day. The shaft which surmounts Bunker Hill is but a modern way of memorizing an event which in earlier ages would have led to the erection of a mound, and the polished monument which marks the resting place of some distinguished man was raised for the same purpose as the mounds heaped over the chiefs and warriors of another age. The feeling which moves us to crown with steeples or spires our houses of worship is evidently akin to that which induced older races to erect a mound on which to place their temples, their idols, and altars of sacrifice.
If mounds were the only works remaining of these ancient people, we would not take so great an interest in them, and, as it is, we are not to suppose that all the mounds are the works of those people we call the Mound Builders. Recent investigation and historical evidence unite in showing that some comparatively recent Indian tribes formed and used mound structures. Early explorers have left abundant testimony to show that in many cases the Indians resorted to mound-burial. Thus, it seems that it was the custom of the Iroquois every eighth or tenth year, or whenever about to abandon a locality, to gather together the bones of their dead and rear over them a mound. To this custom, which was not confined to the Iroquois, are doubtless to be ascribed the barrows and bone mounds which have been found in such numbers in various parts of the country.17 Although it is well to bear these facts in mind, yet it is not doubted that the larger number, and especially the more massive ones, were erected by the same people who built the other mysterious works, and so it is necessary that they be carefully studied.
In the valley of the Ohio there have been found a class of mounds known as Altar Mounds. These, it should be stated, nearly always occur in or near inclosures. This cut gives us a good idea of mounds of this kind. Near the top is seen an instance of what is called “intrusive” burial. After the mound was completed it had been dug into and a body buried near the surface. This burial was evidently later in time, and had no connection with the purpose for which the mound was originally built. We also notice in this mound the different layers of which it was composed. These layers are of gravel, earth, and sand, the latter being only a few inches thick. Mounds made in this manner are called stratified mounds, and all altar mounds are probably of this kind. The lines of stratification have been described as curving so as to correspond with the shape of the mound, and such we are told is the general rule.18