+28.+ By assiduously working the battering rams the Romans were always breaking down this or that part of the wall. But yet they could not succeed in storming any of these breaches, because the besieged were energetic in raising counter walls, and the Aetolians fought with determined gallantry on the débris. They, therefore, in despair had recourse to mines and underground tunnels. Having safely secured the central one of their three works, and carefully concealed the shaft with wattle screens, they erected in front of it a covered walk or stoa about two hundred feet long, parallel with the wall; and beginning their digging from that, they carried it on unceasingly day and night, working in relays. For a considerable number of days the besieged did not discover them carrying the earth away through the shaft; but when the heap of earth thus brought out became too high to be concealed from those inside the city, the commanders of the besieged garrison set to work vigorously digging a trench inside, parallel to the wall and to the stoa which faced the towers. When the trench was made to the required depth, they next placed in a row along the side of the trench nearest the wall a number of brazen vessels made very thin; and, as they walked along the bottom of the trench past these, they listened for the noise of the digging outside. Having marked the spot indicated by any of these brazen vessels, which were extraordinarily sensitive and vibrated to the sound outside, they began digging from within, at right angles to the trench, another underground tunnel leading under the wall, so calculated as to exactly hit the enemy’s tunnel. This was soon accomplished, for the Romans had not only brought their mine up to the wall, but had underpinned a considerable length of it on either side of their mine; and thus the two parties found themselves face to face. At first they conducted this underground fighting with their spears: but as neither side could do much good, because both parties protected themselves with shields and wattles, some one suggested another plan to the defenders. Putting in front of them an earthenware jar, made to the width of the mine, they bored a hole in its bottom, and, inserting an iron funnel of the same length as the depth of the vessel, they filled the jar itself with fine feathers, and putting a little fire in it close to the mouth of the jar, they clapped on an iron lid pierced full of holes. They carried this without accident through the mine with its mouth towards the enemy. When they got near the besiegers they stopped up the space all round the rim of the jar, leaving only two holes on each side through which they thrust spears to prevent the enemy coming near the jar. They then took a pair of bellows such as blacksmiths use, and, having attached them to the orifice of the funnel, they vigorously blew up the fire placed on the feathers near the mouth of the jar, continually withdrawing the funnel