addition, the Platæans met them by breaking a hole in the lower part of their town wall, and pulling in the earth from the lower portion of the mound; which thus gave way at the top and left a vacant space near the wall, until the besiegers filled it up by letting down quantities of stiff clay rolled up in wattled reeds, which could not be pulled away in the same manner. Again, the Platæans dug a subterranean passage from the interior of their town to the ground immediately under the mound, and thus carried away unseen the lower earth belonging to the latter; so that the besiegers saw their mound continually sinking down, in spite of fresh additions at the top,—yet without knowing the reason. Nevertheless, it was plain that these stratagems would be in the end ineffectual, and the Platæans accordingly built a new portion of town wall in the interior, in the shape of a crescent, taking its start from the old town wall on each side of the mound: the besiegers were thus deprived of all benefit from the mound, assuming it to be successfully completed; since when they had marched over it, there stood in front of them a new town wall to be carried in like manner. [328] Thucyd. ii, 75. Nor was this the only method of attack employed. Archidamus farther brought up battering engines, one of which greatly shook and endangered the additional height of wall built by the Platæans over against the mound; while others were brought to bear on different portions of the circuit of the town wall. Against these new assailants, various means of defence were used: the defenders on the walls threw down ropes, got hold of the head of the approaching engine, and pulled it by main force out of the right line, either upwards or sideways: or they prepared heavy wooden beams on the wall, each attached to both ends by long iron chains to two poles projecting at right angles from the wall, by means of which poles it was raised up and held aloft: so that at the proper moment, when the battering machine approached the wall, the chain was suddenly let go, and the beam fell down with great violence directly upon the engine and broke off its projecting beak.[329] However rude these defensive processes may seem, they were found effective against the besiegers, who saw themselves, at the close of three months’ unavailing efforts, obliged to renounce the idea of taking the town in any other way than by the process of blockade and famine,—a process alike tedious and costly.[330] [329] The various processes, such as those here described, employed both for offence and defence in the ancient sieges, are noticed and discussed in Æneas Poliorketic. c. 33, _seq._ [330] Thucyd. ii, 76.