Medieval artillery consisted of three types of stone-throwing machines (petraria): the ballista, which worked on the principles of the slingshot or catapult; the mangonel, which worked by torsion; and the trebuchet, or beam, which consisted of a sling and counterweight. These machines hurled rocks of various sizes, making ammunition a renewable resource. Their range was 90–300 yards. The ballista shot bolts like a large crossbow. The huge mangonel could throw stones weighing over 200 pounds a distance of over 200 yards—more than twice the length of a modern football field (Figure 14). The most powerful and accurate weapon (far more effective than the early cannons) was the trebuchet, which had a range of about 300 yards. The trebuchet consisted of a beam on a pivot, having a bucket weighted with stones and earth at one end and a sling for the missile at the other end. Operated by a team of up to sixty men, the trebuchet fired huge boulders that shook the walls and broke through the crenellations and machicolations. Its sling could also be filled with rubbish, garbage, and even dead men and animals, which it slung over castle walls to insult, terrify, spread disease, and infect the water and food supplies. A trebuchet required almost half an hour to load and fire. The trebuchet was invented late in the twelfth century; its earliest use in England was by barons against King John in 1215–16. In the next century Edward I of England was so proud of his trebuchet (named “War Wolf”) that in 1309 he had a reviewing platform built so that the queen and her ladies could watch the machine in action during a siege in Scotland. None of these war machines survive, although modern reenactors have built and tested them. At the castle of Chinon one can see a modern reproduction set out in the ditch between the forebuilding and the main castle. The medieval city of Les Baux in southern France has a collection of reconstructed siege weapons.