The most remarkable group of prehistoric fortifications in North America is perhaps that near Newark, in the valley of the Scioto. It includes an octagonal _enceinte_ eighty acres in area, a square _enceinte_ of twenty acres, with two others, one twenty the other thirty acres in extent. The walls of the great circle are still twelve feet high by fifty feet wide at the base. They are protected by an interior fosse seven feet deep by thirty-five feet wide. According to measurements carefully made by Colonel Whittlesey,27 the total area covered by these intrenchments is no less than twelve square miles, and the length of the mounds exceeds two miles. The large entrances protected by mounds thirty-five feet high, the avenues leading to them which are regular labyrinths, the quaintly shaped mounds—one, for instance, represents the foot of a gigantic bird—all combine to strike the visitor with astonishment. We give a representation (Fig. 86) of a group, not unlike that we have just described, which is situated at Liberty (Ohio), and includes two circles and one square. The diameter of the great circle is 1,700 feet, and it encloses an area of forty acres, whilst that of the smaller _enceinte is 500_ feet; the area of the square, each side of which measures 1,080 feet, is twenty-seven acres. The walls are not strengthened by any ditch, and, contrary to general usage, the earth of which they are made was dug out from the inside of the _enciente_ itself. We may also mention Old Fort (Greenup County, Kentucky, successively described by Caleb Atwater, Squier, and J. H. Lewis. It is situated forty feet above the river, and the total length of the walls exceeds 3,175 feet. Six entrances give access to it, and in the centre rises a mound representing some animal, a bear probably, measuring more than 105 feet. Several small mounds, beneath which were found human bones, cluster about the larger one. [Illustration: 86.] Group at Liberty (Ohio). [Illustration: 87.] Trenches at Juigalpa (Nicaragua). We must not omit to name an extraordinary system of intrenchments at Juigalpa, in Nicaragua, which so far as I know is quite unique. This is a series of trenches extending for several miles (Fig. 87), varying in width from nine and a half to thirteen feet; at equal distances are oval reservoirs, the longest axis of which measures as much as seventy-eight feet. In each reservoir are two or four mounds, probably serving as watch-towers. We know nothing either of the people who erected these singular structures or of the enemy from whom they formed a protection. Nor can anything be guessed as to the way in which the defence was conducted. All is involved in obscurity, and at every turn we are compelled to repeat that prehistoric studies are weighted with uncertainty, long and arduous study being necessary to bring ever so little order into the chaos in which everything connected with them is involved.