The second class of military works, which are exceedingly numerous on all the watercourses—existing not only on the Ohio and Mississippi, but on all their tributaries, especially on the Muskingum, Scioto, Miami, Wabash, Illinois, Kentucky, and minor streams—are mounds which served as outlooks. These were always placed in positions to command extended views, and from which signals could be given to still others of the same character, or probably to settlements remote from the watercourses. [Illustration: Square Mound, Marietta.] A system of these works no doubt formerly existed on the Great Miami River extending north of Dayton, Ohio, southward to the Ohio River, and connected with the great settlement on the site of Cincinnati and with the high bluffs on the Kentucky shore. The great Mound at Miamisburgh, ten miles south of Dayton, formed a part of this chain. This monster mound is sixty-eight feet high and 852 feet in circumference, and may have served the double purpose of a signal station and the base of a small edifice devoted to astronomical or religious purposes. There is little doubt that the Mound-builders in the latter period of their occupancy of this region, when apprehensive of danger from their enemies, employed a system of signal telegraph by which communication was had, through means of the watch-fire or the torch, between localities as distant as those now occupied by Cincinnati and Dayton. Only a few minutes were necessary by means of such a perfected system in which to transmit a signal fifty or one hundred miles. Squier and Davis remark on this subject: “There seems to have existed a system of defences extending from the sources of the Alleghany and Susquehanna in New York, diagonally across the country, through Central and Northern Ohio to the Wabash. Within this range the works which are regarded as defensive are largest and most numerous.” The signal system we have reason to believe was employed throughout the entire extent of this range of works. The majority of the enclosures found in the Ohio and Mississippi valleys are presumed not to have been designed for military purposes, since the trench is usually _inside_ of the embankment. However, instances of the trench being outside of the parapet occur in Southern Ohio.[34] The most magnificent Mound-builder remains in Ohio are the extensive and intricate works near Newark in Licking County. The survey made by Col. Whittlesey and published in the _Ancient Monuments of the Mississippi Valley_, is the most reliable as well as the fullest source of our information concerning their magnitude, though the plan has been corrected considerably by more recent surveys. These works occupy an area of two miles square, and formerly consisted of twelve miles of embankment. The spacious gateways—one of which has embankments on both sides measuring thirty-five feet in height from the bottom of the interior trench—the labyrinthine system of avenues, the strangely-shaped mounds,