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described; but tbeir fronts are formed on a triangularplan, so that the weapons from the wall may not falldirect on the faces, but gliding off from them, the exca-vators within may be secure from danger. It does notappear to me foreign to our purpose to explain the pro-portions and constructions of the tortoise made by Agetorthe Byzantine. Its base was sixty feet long, its widtheighteen. The upright pieces which rose above theframing, were four in number ; they were in two lengths,joined, each thirty-six feet high, one foot and one palmin thickness, and in width one foot and a half. Thebase had eight wheels, on which it was moved; theirheight was six feet and three-quarters, their thicknessthree feet, composed of three pieces of wood dove-tailedtogether, and tied with plates of cold wrought iron.These turned on naves, or hamaxopodes, as they arecalled. Above the surface of the cross pieces whichwere on the base, upright posts were erected, eighteenfeet and a quarter high, three-quarters wide, and three-twelfths thick, and one and three-quarters apart. Abovethem were beams all round, which tied the machine to-gether ; they were one foot and a quarter wide, and three-quarters thick. Over these the braces were placed, andwere twelve feet high. Above the braces was a beamwhich united the framing. They had also side piecesfixed transversely, on which a floor, running round them,covered the parts below. There was also a middle floorabove the small beams, where the scorpions and cata-pultae were placed. Two upright pieces were alsoraised, joined together, thirty-five feet long, a foot and ahalf thick, and two feet wide, united at their heads,dove-tailed into a cross beam, and by another in themiddle, morticed between two shafts and tied with ironhooping, above which were alternate beams between theuprights and the cross piece, firmly held in by thecheeks and angle pieces. Into the framing were fixedtwo round and smooth axles, to which were fastened the