Having seen only a few mounds in Illinois, Indiana and Kentucky, I must confine my paper to those found in the State of Ohio, where, during a residence of seventeen months, I made the closest investigation my time and duties permitted. In Ohio, the number of mounds, including enclosures of different kinds, is estimated at about 13,000, though it requires the greatest care to distinguish between the mounds proper and those subsequently erected by the Indians. In some parts they are very close together, which is strong evidence that these regions were densely populated. In others, a solitary mound, with adjacent burial mounds, gives us the idea of a rural village or town. ENCLOSURES.--In the State of Ohio, alone, there have been found 1,500 enclosures. Some of these have walls ranging in height from three to thirty feet, enclosing areas of from ten to 400 acres. Those areas, enclosed by strong walls, erected in regions difficult of access, were undoubtedly intended as military enclosures; while those areas enclosed by slight walls, with no mounds to cover the openings, were intended as sacred enclosures. I shall leave the consideration of the sacred enclosures until I describe the temple, or sacrificial mounds, giving a brief outline of some of the famous fortifications built by those strange people. Within convenient distance of the city of Xenia, on Little Miami River in Warren county, Ohio, can be seen at any time that famous enclosure known as "Fort Ancient." There can be no mistake as to the intention of this wonderful enclosure. It is situated on the east bank of the Miami on a most commanding position. On the east, two ravines originate, running on either side towards the river, leaving the great fortress on an elevation of 230 feet above the river. The whole is surrounded by a wall of five miles in length, but owing to the uneven course of the river, there are only enclosed one hundred acres. The wall has numerous openings, which, however, are well protected by inner walls, or mounds. These openings could be occupied by warriors while the interior would not be exposed to the enemy. Within the enclosure are disposed twenty-four reservoirs, which could be dexterously connected with springs, so that in time of siege, they would be comparatively independent. The strength of this fortress does not depend on the walls alone, which range in height from five to twenty feet, but upon its isolated position and steep sides. Near the fortification are two large mounds from which run two parallel walls for 1,350 feet, and then unite, enclosing another mound. We cannot tell what part these outer walls and mounds played in the defence of this fortification. But we know that all give evidence of an immense garrison occupied by an ancient and somewhat civilized race, whose numerous enemies, doubtless, forced such strong defence. In point of inaccessibility, engineering skill, and strength, this famous