That the Mound-Builders and their works belong to a distant period in the past is evident; but, of course, we have no means of determining their antiquity with any approach to accuracy, no scheme of chronology by which their distance from us in time can be measured. Nevertheless, some things observed in their remains make it certain that the works are very ancient.

1. One fact showing this is pointed out by those who have examined them carefully as follows: None of these works (mounds and inclosures) occur on the lowest-formed of the river terraces, which mark the subsidence of the western streams; and as there is no good reason why their builders should have avoided erecting them on that terrace, while they raised them promiscuously on all the others, it follows, not unreasonably, that this terrace has been formed since the works were erected. It is apparent, also, that in some cases the works were long ago partly destroyed by streams which have since receded more than half a mile, and at present could not reach them under any circumstances. Those streams generally show four successive terraces, which mark four distinct eras of their subsidence since they began to flow in their present courses. The fourth terrace, on which none of the works are found, marks the last and longest of these periods; and it marks also the time since the Mound-Builders ceased to occupy the river-valleys where it was formed. The period marked by this fourth terrace must be the longest, because the excavating power of such streams necessarily diminishes as their channels grow deeper. This geological change, which has taken place since the latest of the mounds and inclosures were constructed, shows that the works are very old; no one can tell how old. To count the years is impossible; but we can see that the date, if found, would take us back to a remote period in the past.

2. Great antiquity is indicated by the skeletons taken from the mounds. Every skeleton of a Mound-Builder is found in a condition of extreme decay. It sometimes appears that the surface of a mound has been used by the wild Indians for interments; but their skeletons, which are always found well preserved, can be readily distinguished by their position in the mounds, as well as by other peculiarities. The decayed bones of Mound-Builders are invariably found within the mounds, never on the surface, usually at the bottom of the structure, and nearly always “in such a state of decay as to render all attempts to restore the skull, or, indeed, any part of the skeleton, entirely hopeless.” Not more than one or two skeletons of that people have been recovered in a condition suitable for intelligent examination. It is stated in the work of Squier and Davis that the only skull belonging incontestably to an individual of the Mound-Building race, which has been preserved entire, was taken from a mound situated on a knoll (itself artificial apparently) on the summit of a hill, in the Scioto Valley, four miles below Chillicothe.

What, save time itself, can have brought these skeletons to a condition in which they fall to pieces when touched, and are ready to dissolve and become dust? All the circumstances attending their burial were unusually favorable for their preservation. The earth around them has invariably been found “wonderfully compact and dry.” And yet, when exhumed, they are in such a decomposed and crumbling condition that to restore them is impossible. Sound and well-preserved skeletons, known to be nearly two thousand years old, have been taken from burial-places in England, and other European countries less favorable for preserving them. The condition of an ancient skeleton can not be used as an accurate measure of time, but it is sufficiently accurate to show the difference between the ancient and the modern, and in this case it allows us to assume that these extremely decayed skeletons of the Mound-Builders are much more than two thousand years old.

Those familiar with the facts established by geologists and palÆontologists are aware that remains of human skeletons have been discovered in deposits of the “Age of Stone” in Western Europe; not to any great extent, it is true, although the discoveries are sufficient to show that fragments of skeletons belonging to that age still exist. It is not without reason, therefore, that the condition of decay in which all skeletons of the Mound-Builders are exhumed from their burial-places is considered a proof of their great antiquity. There is no other explanation which, so far as appears, can be reasonably accepted.

3. The great age of these mounds and inclosures is shown by their relation to the primeval forests in which most of them were discovered. I say primeval forests, because they seemed primeval to the first white men who explored them. Of course there were no unbroken forests at such points as the Ohio Valley, for instance, while they were occupied by the Mound-Builders, who were a settled agricultural people, whose civilized industry is attested by their remains. If they found forests in the valleys they occupied, these were cleared away to make room for their towns, inclosures, mounds, and cultivated fields; and when, after many ages of such occupation, they finally left, or were driven away, a long period must have elapsed before the trees began to grow freely in and around their abandoned works. Moreover, observation shows that the trees which first make their appearance in such deserted places are not regular forest trees. The beginning of such growths as will cover them with great forests comes later, when other preliminary growths have appeared and gone to decay.

When the Ohio Valley was first visited by Europeans it was covered by an unbroken forest, most of the trees being of great age and size; and it was manifest that several generations of great forest trees had preceded those found standing in the soil. The mounds and inclosures were discovered in this forest, with great trees growing in them. Eight hundred rings of annual growth were counted in the trunk of a tree mentioned by Sir Charles Lyell and others, which was found growing on a mound at Marietta. In the same way, successive generations of forest trees had grown over their extensive mining works near Lake Superior, and many of those works are still hidden in what seem to be primeval forests.

General Harrison made the following suggestion in regard to the establishment of these forests in Ohio. When the individual trees that first got possession of the soil had died out one after another, they would, in many cases, be succeeded by other kinds, till at last, after a great number of centuries, that remarkable diversity of species characteristic of North America would be established. His suggestion, the result of practical observation and study, is not without reason. It is certain, in any case, that the period when these old constructions were deserted is so far back in the past, that sufficient time has since passed for the abandoned towns and fields to remain for years, and perhaps centuries, as waste places, pass through the transition from waste lands to the beginning of forest growths, and then be covered by several generations of such great forest trees as were cleared away to prepare the soil for the settlements, towns, and farms of our people.

HOW LONG WERE THEY HERE?

There are many indications to warrant the conclusion that the Mound-Builders occupied their principal seats in the Ohio and Mississippi Valleys during a very long period. If they came from the south, as appears evident, their settlements must have been extended up the valley gradually. After their first communities were established in the Gulf regions, considerable time must have elapsed before their advancing settlements were extended northward, through the intervening region, into the Valley of the Ohio. On the Ohio and in the valleys of its tributaries their settlements were very numerous, and evidently populous. The surprising abundance of their works in this region, which have been traced in our time, shows that they dwelt here in great numbers, and had no lack of industry.

This region seems to have been one of the principal centres from which their settlements were advanced into the western part of Virginia; into Michigan, Wisconsin, Iowa, Illinois, Indiana, and Missouri. The spread of their settlements was necessarily gradual, and a long period must have been required to extend them over all the country where remains of their works are known to exist. If their civilization was chiefly developed after their arrival in the country, which is unlikely, many years must have elapsed before colonies went forth, to any great extent, from the original seat of its development. In any case, time was required to make their chief settlements sufficiently old and populous to send forth colonies. It is manifest in their remains that the communities of this ancient people most remote from the populous centres on the Ohio, east, north, and west, were, like all border settlements, the rudest and least populous. The remains at these points do not indicate either as much wealth or as many workers, and the places where these borderers settled must have been the latest occupied and the earliest abandoned. One diligent investigator, who believes they came originally from Mexico, speaks of the time of their stay in the country as follows:

“When we consider the time required to people the whole extent of the territory where their remains are found, and bring that people into a condition to construct such monuments, and when we reflect on the interval that must have passed after their construction until the epoch of their abandonment, we are constrained to accord them a very high antiquity.”

He points out that they were sun worshipers, like the Mexicans and Peruvians, and calls attention to the disks dug from their mounds, which appear to have been designed as representations of the sun and moon.

Their long occupation of the country is suggested by the great extent of their mining works. All who have examined these works agree with Colonel Whittlesey that they worked the Lake Superior copper mines “for a great length of time.” How long they had dwelt in the Ohio Valley when this mining began can not be told, but a very considerable period must have elapsed after their arrival at that point before the mines were discovered. We can not suppose the first settlers who came up from the Gulf region to the Ohio Valley went on immediately, through the wilderness a thousand miles, to hunt for copper mines on Lake Superior; and, even after they began to explore that region, some time must have passed before the copper was found.After they discovered the mines and began to work them, their progress could not have been rapid. As their open trenches and pits could be worked only in the summers, and by methods that made their operations much slower than those of modern miners, no great advance of their work was possible during the working time of each season; and yet remains of their mining works have been discovered wherever mines have been opened in our day; and, as previously stated, they are known to exist in heavy forests, where the modern mining works have not yet been established. There is nothing to indicate that they had settlements any where in the mining region. Colonel Whittlesey, and others whose study of the subject gives their opinion much weight, believe the Mound-Builders went up from the settlements farther south in the summers, remained in the copper region through the season, and worked the mines in organized companies until the advance of winter terminated their operations.

Colonel Whittlesey says: “As yet, no remains of cities, graves, domiciles, or highways have been found in the copper region;” and adds, “as the race appears to have been farther advanced in civilization than their successors, whom we call aborigines, they probably had better means of transportation than bark canoes.” It may be said, also, that the accumulations called wealth were necessary to make this regular and systematic mining possible. Without these they could not have provided the supplies of every kind required to sustain organized companies of miners through a single season. A great many summers must have passed away before such companies of miners, with all needed tools and supplies, could have made their works so extensive by means of such methods as they were able to use.

They probably occupied the country on the Gulf and Lower Mississippi much longer than any other portion of the great valley. Their oldest and latest abandoned settlements appear to have been in this region, where, we may reasonably suppose, they continued to dwell long after they were driven from the Ohio Valley and other places at the north.

The Natchez Indians found settled on the Lower Mississippi may have been a degenerate remnant of the Mound-Builders. They differed in language, customs, and condition from all other Indians in the country; and their own traditions connected them with Mexico. Like the Mexicans, they had temples or sacred buildings in which the “perpetual fire” was maintained. Each of their villages was furnished with a sacred building of this kind. They had also peculiarities of social and political organization different from those of other tribes. They were sun-worshipers, and claimed that their chief derived his descent from the sun. The Natchez were more settled and civilized than the other Indians, and, in most respects, seemed like another race. One learned investigator classes them with the Nahuatl or Toltec race, thinks they came from Mexico, and finds that, like the ancient people of Panuco and Colhuacan, they had the phallic ceremonies among their religious observances. Their history can not be given, and there is little or nothing but conjecture to connect them with the Mound-Builders. The Natchez were exterminated in 1730 by the French, whom they had treated with great kindness. Of the few who escaped death, some were received among the Chickasaws and Muskogees, but more were sent to Santo Domingo and sold as slaves.

No view that can be taken of the relics left by the Mound-Builders will permit us to believe their stay in the country was short. Any hypothesis based on the shortest possible estimate of the time must count the years by centuries.