Liber III, Pars III — Quae, et quot sunt genera machinarum eiicientium Lapides; per quae impugnari possunt munitiones obsessae, et devinci possunt civitates et castrae. Cap. XVIII.

Liber III, Pars III — Quae, et quot sunt genera machinarum eiicientium Lapides; per quae impugnari possunt munitiones obsessae, et devinci possunt civitates et castrae. Cap. XVIII.

It often happens that some besieged fortifications are built over very strong stones, or are surrounded by water, or have very deep ditches, or are fortified in some other way. So that they can never be taken through the streets and underground passages, or only with great difficulty. It also often happens that if a besieged fortification can be taken through underground passages, the defenders, however, prevent the digging, so that they are not taken by surprise or through traps. We will show how this should be done in the following chapters, where we will discuss defensive warfare. For when we discuss how the besieged should defend themselves, it will be explained how they should provide for their defense through tunnels and other devices of the besiegers. Therefore, if the method of the art should imitate nature, which always produces results through the easier way: since fortifications cannot be attacked as easily through streets as through stone machines, or through buildings pushed up to the walls of a castle or besieged city, it is necessary to use such arguments to achieve the intended goal. It must therefore be seen how many types of stone machines there are, and how many methods of buildings through which fortifications can be attacked. Stone machines, however, are classified into four types. In every such machine, there must be something that pulls and raises the arm of the machine, to which the sling is attached, from which stones are thrown. This elevation of the arm sometimes happens through a counterweight, but sometimes the counterweight is not sufficient, and further, the arm of the machine is raised with ropes, from which stones are thrown. If, therefore, the projection is solely due to the counterweight, that counterweight can be either fixed, or it can be mobile, or it can be a combination of both. A counterweight is said to be fixed when there is a certain box that adheres immovably to the arm, filled with stones and sand, or filled with lead, or some other heavy body; this type of machine the ancients called Trabutium. Among other machines, this one projects straight because the counterweight always pulls uniformly; therefore, it always propels in the same way, as this machine could strike like a dart. For when a target is to be struck by it, if it throws too far to the right, it must be turned to the left, or if it throws too far to the left, it must be turned to the right to aim at the place where the stone is to be thrown. If, however, it throws too high, either the machine must be moved closer to the target, or a heavier stone must be placed in its sling, which it cannot lift as easily. If, however, it throws too low or too far, the machine must be moved closer, or the stone must be lightened. The stones of these machines must always be considered carefully if they are to be thrown accurately at a specific target. Another type of machine has a counterweight that is attached flexibly around the arm or around the machine's rod, rotating around this rod. This type of machine was called Biffa by the Roman soldiers. However, this differs from the Trabutio. For since the counterweight adheres flexibly to the machine's arm, although it can pull more due to its motion, it does not pull uniformly, which is why it throws farther than Biffa, but it does not strike as accurately or uniformly. There is also a third type of machine, which they call Tripantum, that has both kinds of counterweights: one fixed to the arm and another that rotates flexibly around it; this one throws more accurately due to the weight fixed in place than Biffa does, but it also throws the stone farther than Trabutio due to the weight that rotates flexibly. The fourth type of machine has ropes instead of a counterweight, which are pulled by the strength and hands of men. Such a machine does not throw stones as large as the three previously mentioned types of machines; however, it does not require as much time to set up as those machines do, so it can throw more frequently and quickly than the others. Therefore, those who besiege a castle or a city must carefully consider whether they can attack that fortification more effectively by throwing stones accurately or farther, or whether they could inflict more damage on the besieged by throwing stones more densely and frequently. For as he sees fit, he can use any of the aforementioned machines, or any of the previously mentioned methods of throwing, or even some of the machines without any of the aforementioned, to attack the castle or the besieged city. If there is complete knowledge of the machines we mentioned, it will be sufficiently clear how any fortification can be attacked using stone-throwing machines. For every type of stone-throwing machine is either one of the aforementioned types or can take its origin from those mentioned. It should also be noted that by day and night, fortifications under siege can be attacked using stone-throwing machines. However, to show how stones thrown from machines strike at night, fire must always be tied to the stone, or a burning wick. For by means of a burning wick tied to the stone, it will be possible to see how the machine throws, and what kind or how heavy a stone is to be placed in the sling of the machine.