While all these preparations for the attack were going on outside, they were also making ready for resistance inside the tower. A tower may be entered by a mine as a cask is bored by an auger; hence a tower is sometimes called a _douve_,[4] and it was the fate of the Tourgue to have its walls pierced by a bung-hole. The powerful boring of two or three hundred-weight of powder had driven a hole through the mighty wall from one side to the other. Beginning at the foot of the tower, it had made a breach in the thickest part of the wall, in a sort of shapeless arch in the lower story of the fortress, and in order to make this hole more practicable for assault from without, the besiegers had enlarged it by cannon-shot. The ground-floor where this breach had penetrated was a large, empty hall of a circular form, with a pillar in the centre, supporting the keystone of the vaulted ceiling. The hall, which was the largest in the keep, was no less than forty feet in diameter. Each story of the tower had a similar room, only on a smaller scale, with guards to the embrasures of the loop-holes. The hall on the ground-floor had neither embrasures, ventilators, nor dormer windows. There was about as much air and light in it as in a tomb. The door of the oubliettes, the greater part of which was iron, was in the lower hall. Another door opened on a staircase leading to the upper rooms. All the staircases were built in the wall itself. It was to the lower hall that the besieged had gained access by the breach they had made; but even after gaining possession of it, the tower would still remain to be taken. One could scarcely breathe in this lower hall, and formerly no one could remain in it twenty-four hours without suffocating; but now, thanks to the breach, one could exist there. For this reason the besieged had not closed the breach. Besides, what purpose would it have served? The guns would have reopened it. They had fastened an iron torch-holder into the wall, wherein they set a torch, and that lighted the lower floor. But how were they to defend themselves? To stop up the hole would have been easy enough, but useless. A _retirade_ would be more effective. A _retirade_ is an intrenchment with a retreating angle,--a kind of barricade composed of rafters, by means of which the fire may be concentrated on the assailants, and which while leaving the breach open from without closes it from within. There was no lack of materials, and they proceeded to construct a barricade of this description with clefts for the passage of gun-barrels. The corner of the _retirade_ was supported by the middle pillar, the two wings touching the walls on either side. Having completed this they placed _fugades_ in safe places. The Marquis directed everything. Inspirer, commander, guide, and master,--a terrible spirit!