“There are two forts, one being an exact circle, the other an exact square. The former is surrounded by two walls, with a deep ditch between them. The latter is encompassed by one wall, without any ditch. The former was sixty-nine rods in diameter, measuring from outside to outside of the circular outer wall; the latter is exactly fifty-five rods square measuring the same way. The walls of the circular fort were at least twenty feet in height, measuring from the bottom of the ditch, before the town of Circleville was built. The inner wall was of clay, taken up probably in the northern part of the fort, where was a low place, and is still considerably lower than any other part of the work. The outside wall was taken from the ditch which is between these walls, and is alluvial, consisting of pebbles worn smooth in water, and sand, to a very considerable depth, more than fifty feet at least. The outside of the walls is about five or six feet in height now; on the inside, the ditch is, at present, generally not more than fifteen feet. They are disappearing before us daily, and will soon be gone. The walls of the square fort are at this time, where left standing, about ten feet in height. There were eight gateways or openings leading into the square fort, and only one into the circular fort. Before each of these openings was a mound of earth, perhaps four feet high, forty feet perhaps in diameter at the base, and twenty or upwards at the summit. These mounds, for two rods or more, are exactly in front of the gateways, and were intended for the defence of these openings.” ... [Illustration: INCLOSURES AT CIRCLEVILLE. Reduced from the survey of Mr. Atwater.] “The extreme care of the authors of these works to protect and defend every part of the circle, is nowhere visible about this square fort. The former is defended by two high walls, the latter by one. The former has a deep ditch encircling it, this has none. The former could be entered at one place only; this at eight, and those about twenty feet broad.” ... “The round fort was picketed in, if we are to judge from the appearance of the ground on and about the walls. Half-way up the outside of the inner wall, is a place distinctly to be seen, where a row of _pickets_ once stood, and where it was placed when this work of defence was originally erected.” ... “What surprised me on measuring these forts, was the exact manner in which they had laid down their circle and square; so that after every effort, by the most careful survey, to detect some error in their measurement, we found that it was impossible, and that the measurement was much more correct than it would have been, in all probability, had the present inhabitants undertaken to construct such a work.”