The largest work is an enclosure marked A in [Plate I], and shown on an enlarged scale in [Plate II]. It is situated on the margin of a bluff overlooking the Little Iowa and an intervening bog-bayou, probably the former channel of the river. It is almost exactly circular, the curve being broken on the east side, where it touches the brink of the bluff, being here made to conform to the line of the latter, though probably never thrown up to the same height as the other portion. The ends at the southeast overlap each other for a short distance, leaving at this point an entrance way, the only one to the enclosure. A ditch runs round on the inside from the entrance on the south to where the wall strikes the bluff on the north, but is wanting along the bluff and overlapping portion. The north and south diameter, measuring from outside to outside, is 277 feet; from east to west, 235 feet; the entire outer circumference is 807 feet, the length of the portion along the bluff 100 feet, and of the overlapping portion at the entrance 45 feet. The wall is quite uniform in size, about 4 feet high and from 25 to 27 in width, except along the bluff, where it is scarcely apparent; the entrance is 16 feet wide, and the ditch 5 to 6 feet wide and 3 feet deep. On the north, adjoining the wall on the outside and extending along it for about 100 feet, is an excavation (c, [Plate II]) 35 feet wide at the widest point and 3 feet deep.
As this ground, including the circle, has been under cultivation for fifteen years, it would be supposed the height of the wall is considerably less than it originally was, but this is probably a mistake. On the contrary, it was originally probably but 20 feet wide and not more than 3 feet high, composed mainly of yellowish brown clay obtained, in part at least, from the ditch, but during occupancy the accumulation of countless bones of animals used as food, stone chips, river shells, broken pottery, and dirt, and, since abandonment, the accumulation of sand drifted by the winds from the crumbling sandstone butte (C, [Plate I]) overlooking it, have not only filled the ditch but elevated the wall and whole interior area 2 feet or more. This accumulation of sand is so great and so uniform over the plateau that fifteen years of cultivation have not sufficed to reach the clay of the original surface nor to unearth or even penetrate to the bones, pottery fragments, and other refuse matter covering the original surface in the circle.
Trenches cut across the wall at various points indicate, first, a layer of sand about 1 foot thick; immediately below this an accumulation of refuse matter forming a layer from 1 to 2 feet thick; under which was the original clay embankment 2 feet thick, resting on the natural surface of the ground. A section of the ditch, embankment, and excavation is shown in [Plate II]. The dotted line a b indicates the natural surface; No. 1 the original clay layer of the wall; No. 2 the layer of earth and refuse material with which the ditch is filled; and No. 3 the top layer of sand.
In No. 2 were found charcoal, ashes, fragments of pottery, fractured bones, etc.
A broad belt of the inner area on the east side was explored, and the same conditions were found to exist here as were revealed by the trenches across the wall and ditch, except that here the shells were more abundant in layer No. 2, and there were many burnt stones.
On the southeastern portion of the plateau (B, [Plate I]) are six nearly parallel lines of mounds running northeast and southwest, mostly circular in form, varying from 15 to 40 feet in diameter, and from 2 to 6 feet in height; a few, as indicated in the figure, are oblong, varying in length from 50 to 100 feet. The number in the group exceeds one hundred.
While engaged in excavating these mounds Colonel Norris observed a number of patches of the level area quite destitute of vegetation. The owner of the land, who was present, could give no explanation of this phenomenon, simply remarking that they had always been so, never having produced a good crop of anything, although there was no apparent difference between the soil of these spots and the surface around them. As some of these extended across the area occupied by the mound group, he concluded to explore them, and was surprised to find them to be burying places, and scattered here and there among the graves, if such they could be called, were stone chips, shells, charcoal, and ashes. He was surprised at this, as he supposed the mounds alone were used as depositories of the dead, and was at first disposed to attribute these burials to a people who had occupied the ground long subsequent to the authors of the works. Possibly this may be the correct solution, but if so, they were certainly the same as those who buried in the mounds of this group, as no difference in the contents and internal arrangement could be observed. In both cases there was a compact layer of hard, light-colored earth, having the appearance of lime-mortar, possibly clay and ashes mixed together, which had been subject to the action of fire. As the burials in these sterile spots were seldom more than 18 inches deep, the only layer above them consisted of sand from the butte, while the mounds were uniformly covered with a layer of richer soil, although below this and covering the skeletons was a layer of hard, light-colored earth. Skeletons and bones were found in great abundance in the mounds and under the surface of the plateau, though none were discovered in the circle or nearer than 200 yards of it. They were sometimes mingled promiscuously with charcoal and ashes, but were usually in whole skeletons lying horizontally, though some were in a sitting posture; they were within from 1 to 3 feet of the surface, without any apparent system, except that they were always covered with a layer of hard earth.
A trench cut through the long mound of this group, No. 1, revealed near the center an oblong pile of sandstones, beneath which was found a rude stone coffin, formed by first placing flat sandstone slabs on the natural surface of the ground, then other slabs at the sides and ends, and a covering of similar stones, thus forming a cist or coffin about 6 feet long and 18 inches wide. Within this, extended at full length, with the head west, was the skeleton of an adult, but too much decayed for preservation. With it were some stone chips, rude stone scrapers, a Unio shell, and some fragments of pottery similar to those dug up in the circular enclosure.
The mounds on the sand butte marked C, [Plate I], which is something over 100 feet high, were opened and found to be in every respect similar to those already mentioned, showing them to be the work of the same people who built the others.
The three mounds in the square enclosures marked D, ([Plate I]), were also opened, with the following results: The largest, oval in form, 30 feet long, about 20 feet broad and 4 feet high, was found to consist of a top layer of loose sand 1 foot thick, the remainder of hard yellowish clay. In the latter were found several flat sandstone fragments, and beneath them, on the original surface of the ground, a much decayed skeleton, with which were a few stone chips, Unio shells, and fragments of pottery.