1. The tortoise contrived for filling up ditches, which also affords an access to the walls, is thus made. A base, called by the Greeks escavra, is prepared twenty-five feet square, with four cross pieces. These are tied in by two other pieces, one twelfth high, and one half wide, distant from each other about a foot and a half, and under each of their intervals are placed the naves of wheels, called in Greek aJmaxovpodeV, within which the axles of the wheels turn in iron hoops. The naves are so made that they have holes in their heads, in which the handspikes being received, are made to turn them. The naves thus revolving, it may be moved forward or backward, to the right or left, or diagonally, as wanted.
2. Above the base are placed two beams, projecting six feet on each side; round the projections of which two other beams are fixed in front, seven feet long, and their width and thickness as described for the base. Upon this frame which is to be morticed, posts are placed, nine feet high, exclusive of their tenons, one foot and a palm square, and a foot and a half distant from each other. These are tied in at top by means of morticed beams. Above these beams are braces, with tenons, the end of one being let into the next to the height of nine feet, and over the braces is a square piece of timber, by which they are connected.
3. They 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.

Chapter 15

1. There is another species of tortoise, which is just the same as that above described, except in respect of the braces. This has a parapet and battlements of boarding, and above, an inclined pent-house round it, tied in at top with planks and hides firmly fastened. Over these is a layer of clay with hair, of such thickness as to prevent the machine taking fire. These machines may be made with eight wheels, if need be, and if the nature of the place require it. The tortoises made for undermining, called by the Greeks o[rugeV, are similar to those already described; but their fonts are formed on a triangular plan, so that the weapons from the wall may not fall direct on the faces, but gliding off from them, the excavators within may be secure from danger.

Tortoise of Hegetor or Agetor of Byzantium

2. It does not appear to me foreign to our purpose to explain the proportions and constructions of the tortoise made by Agetor (or Hegetor) the Byzantine. Its base was sixty feet long, its width eighteen. The upright pieces which rose above the framing, were four in number; they were in two lengths, joined, each thirty-six feet high, one foot and one palm in thickness, and in width one foot and a half. The base had eight wheels, on which it was moved; their height was six feet and three quarters, their thickness three feet, composed of three pieces of wood dove-tailed together, and tied with plates of cold wrought iron.
3. These turned on naves, or hamaxopodes, as they are called. Above the surface of the cross pieces which were on the base, upright posts were erected, eighteen feet and a quarter high, three quarters wide, and three-twelfths thick, and one and three quarters apart. Above them were beams all round, which tied the machine together, they were one foot and a quarter wide, and three quarters thick. Over these the braces were placed, and were twelve feet high. Above the braces was a beam which united the framing. They had also side pieces fixed transversely, on which a floor, running round them, covered the parts below.
4. There was also a middle floor above the small beams, where the scorpions and catapultæ were placed. Two upright pieces were also raised, joined together, thirty-five feet long, a foot and a half thick, and two feet wide, united at their heads, dove-tailed into a cross beam, and by another in the middle, morticed between two shafts and tied with iron hooping, above which were alternate beams between the uprights and the cross piece, firmly held in by the cheeks and angle pieces. Into the framing were fixed two round and smooth axles, to which were fastened the ropes that held the ram.
5. Over the heads of those who worked the ram was a pent-house, formed after the manner of a turret, where two soldiers could stand secure from danger, and give directions for annoying the enemy. The ram was one hundred and six feet long, a foot and a palm wide at the butt, a foot thick, tapering towards the head to a foot in width, and five-eighths in thickness.
6. It was furnished with a hard iron beak like those fixed on galleys, from which went out four iron prongs about fifteen feet long, to fix it to the beam. Moreover, distributed between the foot and the head of the beam, four stout ropes were stretched eight inches thick, made fast like those which retain the mast of a ship between the poop and the prow. To these were slung others diagonally, which suspended the ram at the distance of a palm and a foot from each other. The whole of the ram was covered with raw hides. At the further end of the ropes, towards the head, were four iron chains, also covered with raw hides,
7. and it had a projection from each floor, framed with much skill, which was kept in its place by means of large stretched ropes, the roughness of which preventing the feet from slipping, made it easy to get thence on to the wall. The machine could be moved in six directions, straight forward, to the right and left, and from its extent it could be used on the ascending and descending slope of a hill. It could, moreover, be so raised as to throw down a wall one hundred feet in height: so, also, when moved to the right and left, it reached not less than one hundred feet. It was worked by one hundred men, and its weight was four thousand talents, or four hundred and eighty thousand pounds.

Chapter 16

1. I have explained what I thought most requisite respecting scorpions, catapultæ, balistæ, no less than tortoises and towers, who invented them, and in what manner they ought to be made. It did not seem necessary to write on ladders, cranes, and other things of simpler construction; these the soldiers of themselves easily make. Neither are they useful in all places, nor of the same proportions, inasmuch as the defences and fortifications of different cities are not similar: for machines constructed to assault the bold and impetuous, should be differently contrived to those for attacking the crafty, and still dissimilar, where the parties are timid.
2. Whoever, therefore, attends to these precepts, will be able to select from the variety mentioned, and design safely, without further aid, such new schemes as the nature of the places and other circumstances may require. For the defence of a place or army, one cannot give precepts in writing, since the machines which the enemy prepares may not be in consonance with our rules; whence oftentimes their contrivances are foiled by some ready ingenious plan, without the assistance of machines, as was the case with the Rhodians.
3. Diognetus was a Rhodian architect, who, to his honour, on account of his great skill, had an annual fixed salary. At that period, an architect of Aradus, whose name was Callias, came to Rhodes, obtained an audience, and exhibited a model of a wall, whereon was a revolving crane, by means whereof he could suspend an Helepolis near the spot, and swing it within the walls. The wondering Rhodians, when they saw it, took away the salary from Diognetus, and conferred it on Callias.
4. Immediately after this, king Demetrius, who, from his resolution, was surnamed Poliorcetes, prepared to wage war against the Rhodians, and brought in his train Epimachus, a celebrated architect of Athens. This person prepared an helepolis of prodigious expense and of ingenious and laborious construction, whose height was one hundred and twenty-five feet, and its width sixty feet: he secured it, moreover, with hair-cloths and raw hides, so that it might securely withstand the shock of a stone of three hundred and sixty pounds weight, thrown from a balista. The whole machine weighed three hundred and sixty thousand pounds. Callias being now requested by the Rhodians to prepare his machine against the helepolis, and to swing it within the wall, as had promised, confessed he was unable.
5. For the same principles do not answer in all cases. In some machines the principles are of equal effect on a large and on a small scale; others cannot be judged of by models. Some there are whose effects in models seem to approach the truth, but vanish when executed on a larger scale, as we have just seen. With an auger, a hole of half an inch, of an inch, or even an inch and a half, may be easily bored; but by the same instrument it would be impossible to bore one of a palm in diameter; and no one would think of attempting in this way to bore one of half a foot, or larger.
6. Thus that which may be effected on a small or a moderately large scale, cannot be executed beyond certain limits of size. When the Rhodians perceived their error, and how shamefully they had wronged Diognetus; when, also, they perceived the enemy was determined to invest them, and the machine approaching to assault the city, fearing the miseries of slavery and the sacking of the city, they humbled themselves before Diognetus, and requested his aid in behalf of his country.
7. He at first refused to listen to their entreaties; but when afterwards the comely virgins and youths, accompanied by the priests, came to solicit his aid, he consented, on condition that if he succeeded in taking the machine, it should be his own property. This being agreed to, he ordered a hole to be made in that part of the wall opposite to the machine, and gave general as well as particular notices to the inhabitants, to throw on the other side of the hole, through channels made for the purpose, all the water, filth, and mud, that could be procured. These being, during the night, discharged through the hole in great abundance, on the following day, when the helepolis was advanced towards the wall, it sunk in the quagmire thus created: and Demetrius, finding himself overreached by the sagacity of Diognetus, drew off his army.
8. The Rhodians, freed from war by the ingenuity of Diognetus, gave him thanks publicly, and loaded him with honours and ornaments of distinction. Diognetus afterwards removed the helepolis within the walls, placed it in a public situation, and inscribed it thus: “DIOGNETUS PRESENTED THIS TO THE PEOPLE OUT OF THE SPOILS OF WAR.” Hence, in defensive operations, ingenuity is of more avail than machines.
9. A similar circumstance occurred at Chios, where the enemy had got ready sambucæ on board their ships; the Chians, during the night, threw into the sea, at the foot of their wall, earth, sand, and stones; so that when the enemy, on the following day, endeavoured to approach it, the ships got aground on the heaps thus created under water, without being able to approach the wall or to recede; in which situation they were assailed with lighted missiles, and burnt. When, also, the city of Apollonia was besieged, and the enemy was in hopes, by undermining, to penetrate the fortress unperceived; the spies communicated this intelligence to the Apollonians, who were dismayed, and, through fear, knew not how to act, because they were not aware at what time, nor in what precise spot, the enemy would make his appearance.
10. Trypho, of Alexandria, who was the architect to the city, made several excavations within the wall, and, digging through, advanced an arrow’s flight beyond the walls. In these excavations he suspended brazen vessels. In one of them, near the place where the enemy was forming his mine, the brazen vessels began to ring, from the blows of the mining tools which were working. From this he found the direction in which they were endeavouring to penetrate, and then prepared vessels of boiling water and pitch, human dung, and heated sand, for the purpose of pouring on their heads. In the night he bored a great many holes, through which he suddenly poured the mixture, and destroyed those of the enemy that were engaged in this operation.
11. Similarly when Marseilles was besieged, and the enemy had made more than thirty mines; the Marseillois suspecting it, lowered the depth of the ditch which encompassed the wall, so that the apertures of all the mines were discovered. In those places, however, where there is not a ditch, they excavate a large space within the walls, of great length and breadth, opposite to the direction of the mine, which they fill with water from wells and from the sea; so that when the mouths of the mine open to the city, the water rushes in with great violence, and throws down the struts, overwhelming all those within it with the quantity of water introduced, and the falling in of the mine.
12. When a rampart composed of the trunks of trees is raised opposite to a wall, it may be consumed by discharging red hot iron bars against it from the balistæ. When, also, a tortoise is brought up to batter a wall with a ram, a rope with a noose in it may be lowered to lay hold of the ram, which being then raised by means of a wheel and axle above, keeps the head suspended, so that it cannot be worked against the wall: lastly, with burning arrows, and with discharges from the balistæ, the whole machine may be destroyed. Thus all these cities are saved and preserve their freedom, not by machines, but by expedients which are suggested through the ready ingenuity of their architects. I have, in this book, to the best of my ability, described the construction of those machines most useful in peace and war. In the preceding nine I treated of the other branches of Architecture, so that the whole subject is contained in ten books.

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