His advisers were divided in opinion. Some said that Conon was planning to build a _beffroi_. This was a most ambitious undertaking ordinarily used only in great sieges. A _beffroi_ was a movable tower built of heavy timbers and raised to at least the height of the wall attacked. Its front was covered by rawhides to repel arrows and fire-balls. It was worked forward on rollers or clumsy wheels until close to the hostile parapet. Then, when almost touching, a swinging bridge from the summit was flung across to the wall, a host of assailants swarmed up a ladder in the rear and over the bridge to the battlements. The defenders then needed all their valor to keep their castle from speedy capture. [Illustration: AN ATTACK WITH THE AID OF A TOWER (From Viollet-Le-Duc); the moat has been filled up, the tower covered with skins to protect it from fire and rolled up to the wall.] Others in the garrison, however, derided the idea that a _beffroi_ was projected. It would be winter ere such a complicated structure could be completed. They said that the baron was preparing battering rams and a "cat." The battering ram was simply a heavy timber with a metal head, swung by chains from a kind of wooden trestle. Set up close under a wall it was pulled back and forth by ropes, and by repeated blows knocked down the masonry. The "cat" was a long, narrow, tent-shaped structure of heavy timbers covered with hides or iron to turn missiles from the parapets. One end of this was built out until it came into contact with the walls, when skillful miners under its protection quarried their way through the masonry with pickaxes. [Illustration: A MANTELET IN WOOD] These methods were easier to prepare than the _beffroi_, although not so effective. The defenders felt sure they would be used when the attackers were seen making _mantelets_, large wooden shields mounted on small wheels, to protect the crossbowmen when they crept up to clear the walls--a needful preliminary to advancing either the cat or the ram. Their certainty increased when one night, by a sudden rush, Conon's men stormed through the weak palisade of the barbican and, forcing their way near to the walls, began filling up the moat with _fascines_--bundles of fagots. By using his trenchbuts and catapults to best advantage, Sire Gauthier felt confident, however, that he had prevented them from leveling the moat sufficiently to make a firm foundation for siege engines. The Tourfière men, therefore, shouted arrogantly: "Take your time, St. Aliquis hirelings! Your 'Madame Cat' will never gnaw our rats."[74] Presently, after a couple of weeks, the besiegers were seen in great activity, as if arraying themselves for an assault. Gauthier was convinced they were about, in desperation, to try to scale his walls with ladders. Then of a sudden a panic-stricken sergeant ran up to his watchtower. Wafts of smoke were escaping near the foundations of the curtain wall near the gate! [Sidenote: Undermining the Wall]