in the ancient military art, a kind of line of circumvallation drawn round a place in order to besiege it. This was also called periapteichismus. The first thing the ancients went about, when they designed to lay close siege to a place, was the apoteichismus; which sometimes consisted of a double wall or rampart, raised of earth; the innermost to prevent sudden fallies from the town, the outermost to keep off foreign enemies from coming to the relief of the beleaguered. This answered to what are called lines of concentric circumvallation among the moderns.