The mounds of the second series, or burial mounds, are usually composed of black mould or loam, promiscuously intermixed with the lighter-colored subsoil.
BURIAL MOUNDS OF THE ILLINOIS OR UPPER MISSISSIPPI DISTRICT.
This district, as heretofore stated, includes eastern Iowa, northeastern Missouri, and northern and central Illinois as far south as the mouth of the Illinois River.
Although we are justified in concluding that this area was occupied during the mound-building age by tribes different from those residing in the Wisconsin district, yet the distinguishing characteristics are more apparent in the forms of the works than in the modes of burial and internal construction of the burial mounds. We shall see by the illustrations hereafter given that at least one of the types found in one district is common in the other. But this is to be expected and is readily explained by the supposition that the tribes which have occupied these regions moved back and forth, thus one after another coming upon the same area. The absence of evidence of such movements would indicate that the mound-building period was of comparatively short duration, a theory which I believe has not been adopted by any authority, but to which I shall have occasion again to refer. One class of the burial mounds of this district is well represented in a group, explored by the members of the Davenport Academy of Natural Sciences, on the Cook farm, near Davenport, Iowa. The mounds of this group are situated on the immediate bank of the Mississippi at a height not exceeding 8 to 12 feet above high-water mark; they are conical in form and of comparatively small size, varying in height from 3 to 8 feet. Nine of them were opened, of which we notice the following:
In No. 1 the layers from above down were, first, a foot of earth; then a layer of stones 1½ feet thick; then a layer of shells 2 inches thick; next a foot of earth, and lastly a second layer of shells 4 inches thick. Immediately under this, at the depth of 5 feet, were found five skeletons stretched horizontally on the original surface of the ground, parallel to each other, three with heads toward the east and two with heads west. With them were found one sea-shell (Busycon perversum), two copper axes, to which fragments of cloth were attached, one copper awl, an arrow-head, and two stone pipes, one representing a frog.
Mound No. 2, though similar in form and external appearance to the preceding, presented a quite different arrangement internally, as is evident from the vertical section shown in [Fig. 7]. Here there were no layers of shells, but two distinct layers of stones. At the depth of 5 feet eight skulls (five only are shown in the figure), with some fragments of bones were unearthed; these were lying in a semicircle of 5 feet diameter, each surrounded by a circle of small stones (shown at a in the figure). From the position of the skulls and bones it was evident these bodies had been buried in a sitting posture. The articles found accompanying the skeletons were two copper axes, two small hemispheres of copper and one of silver, a bear's tooth, and an arrow-head.
No. 3, though the largest of the group, was apparently unstratified, the original burial consisting of the bones of two adults and one infant, at the original surface of the ground, under a thin layer of ashes, and surrounded by a single circle of small red stones. With these were found copper axes, copper beads, two carved stone pipes (one in the form of a ground-hog), animal teeth, etc. Near the surface of the mound were two well-preserved skeletons, with evidences of an "oakwood" covering over them and accompanied by glass beads, a fire steel, clay pipe, and silver ear-ring—evidently an intrusive burial.