The use of the regular mine for effecting a breach in the wall of a fortified place was well known, and often brought to bear. The miners began their work at some distance, and drove a shaft underground towards the part of the fortifications which seemed most assailable; they excavated beneath the foundations of the wall, supporting the substructure with wooden props until they had finished their work. Then they set fire to the props, and retired to see the unsupported weight of the wall bringing it down in a heap of ruins. The operation of mining was usually effected under the protection of a temporary pent-house, called a _cat_ or _sow_. William of Malmesbury describes the machine as used in the siege of Jerusalem, at the end of the eleventh century. "It is constructed," he says, "of slight timbers, the roof covered with boards and wicker-work, and the sides protected with undressed hides, to protect those who are within, who proceed to undermine the foundations of the walls." Our next woodcut gives a very clear illustration of one of these machines, which has been moved on its wheels up to the outer wall of a castle, and beneath its protection a party of men-at-arms are energetically plying their miner's tools, to pick away the foundation, and so allow a portion of the wall to settle down and leave an entrance. The methods in which this mode of attack was met were various. We all remember the Border heroine, who, when her castle was thus attacked, declared she would make the sow farrow, viz., by casting down a huge fragment of stone upon it. That this was one way of defence is shown in the woodcut, where one of the defenders, with energetic action, is casting down a huge stone upon the sow. That the roof was made strong enough to resist such a natural means of offence is shown by the stones which are represented as lodged all along it. Another more subtle counteraction, shown in the woodcut, was to pour boiling water or boiling oil upon it, that it might fall through the interstices of the roof, and make the interior untenable. No doubt means were taken to make the roof liquid-tight, for the illustration represents another mode of counteraction (of which we have met with no other suggestion), by driving sharp-pointed piles into the roof, so as to make holes and cracks through which the boiling liquid might find an entrance. If these means of counteracting the work of the cat seemed likely to be unavailing, it still remained to throw up an inner line of wall, which, when the breach was made, should extend from one side to the other of the unbroken wall, and so complete the circumvallation. This, we have evidence, was sometimes done with timber and planks, and a sort of scaffolding was erected on the inner side, which maintained the communication along the top of the walls, and enabled the soldiers to man the top of this wooden wall and offer a new resistance to the besiegers as they poured into the breach. The mine