This unsuccessful attack was, after five days' active preparation, followed by another still more desperate, in which the besiegers made use of a huge machine moving upon wheels, and including several platforms or stages, which held various parties of armed soldiers, who were defended by a strong roofing of boards and hides, beneath which they could work their battering-rams with impunity. To co-operate with this unwieldy and bulky instrument, which, from its shape and covering, they called a "sow," movable scaffolds had been constructed, of such a height as to overtop the walls, from which they proposed to storm the town; and, instead of a single vessel, as on the former occasion, a squadron of ships, with their top castles manned by picked bodies of archers, and their armed boats slung mast high, were ready to sail in with the tide, and anchor beneath the walls. Aware of these great preparations, the Scots, under the encouragement and direction of their governor, laboured incessantly to be in a situation to render them unavailing. By Crab, the Flemish engineer, machines similar to the Roman catapult, moving on wheels, and of enormous strength and dimensions, were constructed and placed on the walls at the spot where it was expected the sow would make its approach. In addition to this, they fixed a crane upon the rampart, armed with iron chains and grappling hooks, and large masses of combustibles and fire-faggots, shaped like tuns, and composed of pitch and flax, bound strongly together with tar ropes, were piled up in readiness for the attack. At different intervals on the walls were fixed the espringalds for the discharge of their heavy darts, which carried on their barbed points little bundles of flaming tow dipped in oil or sulphur; the ramparts were lined by the archers, spearmen, and crossbows; and to each leader was assigned a certain station, to which he could repair on a moment's warning.