30 ABORIGINAL MONUMENTS
were examined, four only were found to be exterior to the walls of enclosures, and these were but a few rods distant from the ramparts.
The fact of stratification, in these mounds, is one of great interest and importance. This feature has heretofore been remarked, but not described with proper accuracy ; and has consequently proved an impediment to the recog- nition of the artificial origin of the mounds, by those who have never seen them. The stratification, so far as ob- served, is not horizontal, but always conforms to the convex outline of the mound.* Nor does it resemble the stratifi- cation produced by the action of water, where the layers run into each other, but is defined with the utmost distinct- ness, and always terminates upon reaching the level of the surrounding earth. That it is artificial will, however, need no argument to prove, after an examination of one of the mounds in which the feature occurs; for, it would be dif_i- cult to explain, by what singular combination of “igneous and aqueous” action, stratified mounds were always raised over symmetrical monuments of burned clay or of stone.
The altars, or basins, found in these mounds, are almost invariably of burned clay, though one or two of stone have been discovered. They are symmetrical, but not of uni- form size and shape. Some are round, others elliptical, and others square, or parallelograms. Some are small, measuring barely two feet across, while others are fifty feet
- ® Some of the mounds, on the lower Mississippi, are horizontally stratified,
exhibiting alternate layers, from base to summit. These mounds differ in form from the conical structures here referred to, and were doubtless con- structed for a different purpose. Some are represented as composed of layers of earth, two or three feet thick, each one of which is surmounted by a burned surface, which has been mistaken for a rude brick pavement. Others are com- posed of alternate layers of earth and human remains. Their origin is doubt- Jess to be found in the annual bone burials of the Cherokees and other southern Indians, of which accounts are given by Bartram and other early writers. It is not impossible that, in rare instances, natural elevations have been modified by art so as to serve some of the purposes for which mounds were erected. In such the natural stratification would be preserved.
