‹‹‹ Vitr. 10.14.2 | Table of Contents | Vitr. 10.15.1 ›››
3They also are kept together by side pieces, and are covered with planks of palm, in preference to other wood: if those are not to be procured, by other wood of a strong nature, pine and ash, however, excepted; for they are weak and easily ignited. About the planking are placed gratings, made of slender twigs recently cut, and closely interwoven; and then the whole machine is covered with raw hides, as fresh as can be procured, doubled and stuffed with seaweed or straw steeped in vinegar, in order that it may resist the strokes of the balistæ and the attacks of fire.
3Let the rafters themselves be held together by bridgings, and covered with boards, preferably of holm oak, or, this failing, of any other material which has the greatest strength, except pine or alder. For these woods are weak and easily catch fire. Over the boardings let there be placed wattles very closely woven of thin twigs as fresh as possible. Let the entire machine be covered with rawhide sewed together double and stuffed with seaweed or straw soaked in vinegar. In this way the blows of ballistae and the force of fires will be repelled by them.