‹‹‹ Vitr. 1.5.5 | Table of Contents | Vitr. 1.5.7 ›››
6It is not, however, always necessary to construct them in this manner, except in places where the besiegers might gain high ground very near the walls, from which, over level ground, an assault could be made. In the construction of ramparts, very wide and deep trenches are to be first excavated; the bottom of which must be still further dug out, for receiving the foundation of the wall. This must be of sufficient thickness to resist the pressure of the earth against it.
6The rampart form of defence, however, is not required in all places, but only where outside the wall there is high ground from which an assault on the fortifications may be made over a level space lying between. In places of this kind we must first make very wide, deep ditches; next sink foundations for a wall in the bed of the ditch and build them thick enough to support an earth-work with ease.