16With regard to scorpiones, catapults, and ballistae, likewise with regard to tortoises and towers, I have set forth, as seemed to me especially appropriate, both by whom they were invented and in what manner they should be constructed. But I have not considered it as necessary to describe ladders, cranes, and other things, the principles of which are simpler, for the soldiers usually construct these by themselves, nor can these very machines be useful in all places nor in the same way, since fortifications differ from each other, and so also the bravery of nations. For siege works against bold and venturesome men should be constructed on one plan, on another against cautious men, and on still another against the cowardly.
2And so, if any one pays attention to these directions, and by selection adapts their various principles to a single structure, he will not be in need of further aids, but will be able, without hesitation, to design such machines as the circumstances or the situations demand. With regard to works of defence, it is not necessary to write, since the enemy do not construct their defences in conformity with our books, but their contrivances are frequently foiled, on the spur of the moment, by some shrewd, hastily conceived plan, without the aid of machines, as is said to have been the experience of the Rhodians.
3For Diognetus was a Rhodian architect, to whom, as an honour, was granted out of the public treasury a fixed annual payment commensurate with the dignity of his art. At this time an architect from Aradus, Callias by name, coming to Rhodes, gave a public lecture, and showed a model of a wall, over which he set a machine on a revolving crane with which he seized an helepolis as it approached the fortifications, and brought it inside the wall. The Rhodians, when they had seen this model, filled with admiration, took from Diognetus the yearly grant and transferred this honour to Callias.
4Meanwhile, king Demetrius, who because of his stubborn courage was called Poliorcetes, making war on Rhodes, brought with him a famous Athenian architect named Epimachus. He constructed at enormous expense, with the utmost care and exertion, an helepolis one hundred and thirty-five feet high and sixty feet broad. He strengthened it with hair and rawhide so that it could withstand the blow of a stone weighing three hundred and sixty pounds shot from a ballista; the machine itself weighed three hundred and sixty thousand pounds. When Callias was asked by the Rhodians to construct a machine to resist this helepolis, and to bring it within the wall as he had promised, he said that it was impossible.
5For not all things are practicable on identical principles, but there are some things which, when enlarged in imitation of small models, are effective, others cannot have models, but are constructed independently of them, while there are some which appear feasible in models, but when they have begun to increase in size are impracticable, as we can observe in the following instance. A half inch, inch, or inch and a half hole is bored with an auger, but if we should wish, in the same manner, to bore a hole a quarter of a foot in breadth, it is impracticable, while one of half a foot or more seems not even conceivable.
6So too, in some models it is seen how they appear practicable on the smallest scale and likewise on a larger. And so the Rhodians, in the same manner, deceived by the same reasoning, inflicted injury and insult on Diognetus. Therefore, when they saw the enemy stubbornly hostile, slavery threatening them because of the machine which had been built to take the city, and that they must look forward to the destruction of their state, they fell at the feet of Diognetus, begging him to come to the aid of the fatherland. He at first refused.
7But after free-born maidens and young men came with the priests to implore him, he promised to do it on condition that if he took the machine it should be his property. When these terms had been agreed upon, he pierced the wall in the place where the machine was going to approach it, and ordered all to bring forth from both public and private sources all the water, excrement, and filth, and to pour it in front of the wall through pipes projecting through this opening. After a great amount of water, filth, and excrement had been poured out during the night, on the next day the helepolis moving up, before it could reach the wall, came to a stop in the swamp made by the moisture, and could not be moved forwards, nor later even backwards. And so Demetrius, when he saw that he had been baffled by the wisdom of Diognetus, withdrew with his fleet.
8Then the Rhodians, freed from the war by the cunning of Diognetus, thanked him publicly, and decorated him with all honours and distinctions. Diognetus brought that helepolis into the city, set it up in a public place, and put on it an inscription: “Diognetus out of the spoils of the enemy dedicated this gift to the people.” Therefore, in works of defence, not merely machines, but, most of all, wise plans must be prepared.
9Likewise at Chios, when the enemy had prepared storming bridges on their ships, the Chians, by night, carried out earth, sand, and stones into the sea before their walls. So, when the enemy, on the next day, tried to approach the walls, their ships grounded on the mound beneath the water, and could not approach the wall nor withdraw, but pierced with fire-darts were burned there. Again, when Apollonia was being besieged, and the enemy were thinking, by digging mines, to make their way within the walls without exciting suspicion, and this was reported by scouts to the people of Apollonia, they were much disturbed and alarmed by the news, and having no plans for defence, they lost courage, because they could not learn either the time or the definite place where the enemy would come out.
10But at this time Trypho, the Alexandrine architect, was there. He planned a number of countermines inside the wall, and extending them outside the wall beyond the range of arrows, hung up in all of them brazen vessels. The brazen vessels hanging in one of these mines, which was in front of a mine of the enemy, began to ring from the strokes of their iron tools. So from this it was ascertained where the enemy, pushing their mines, thought to enter. The line being thus found out, he prepared kettles of hot water, pitch, human excrement, and sand heated to a glow. Then, at night, he pierced a number of holes, and pouring the mixture suddenly through them, killed all the enemy who were engaged in this work.
11In the same manner, when Marseilles was being besieged, and they were pushing forward more than thirty mines, the people of Marseilles, distrusting the entire moat in front of their wall, lowered it by digging it deeper. Thus all the mines found their outlet in the moat. In places where the moat could not be dug they constructed, within the walls, a basin of enormous length and breadth, like a fish pond, in front of the place where the mines were being pushed, and filled it from wells and from the port. And so, when the passages of the mine were suddenly opened, the immense mass of water let in undermined the supports, and all who were within were overpowered by the mass of water and the caving in of the mine.
12Again, when a rampart was being prepared against the wall in front of them, and the place was heaped up with felled trees and works placed there, by shooting at it with the ballistae red-hot iron bolts they set the whole work on fire. And when a ram-tortoise had approached to batter down the wall, they let down a noose, and when they had caught the ram with it, winding it over a drum by turning a capstan, having raised the head of the ram, they did not allow the wall to be touched, and finally they destroyed the entire machine by glowing fire-darts and the blows of ballistae. Thus by such victory, not by machines but in opposition to the principle of machines, has the freedom of states been preserved by the cunning of architects.
Such principles of machines as I could make clear, and as I thought most serviceable for times of peace and of war, I have explained in this book. In the nine earlier books I have dealt with single topics and details, so that the entire work contains all the branches of architecture, set forth in ten books.