This work, having to be cut very deep, as it was to go right under the ditch, and being in the hands of untrained volunteers from the infantry, who had no proper cutting tools, advanced very slowly. The soil, fortunately, was favourable, being a stiff argillaceous clay which showed no disposition to crumble up: the gallery was cut as if in stone, with even and perpendicular sides and floor, and no props or timbering were found necessary. The main hindrance to rapid work, over and above the unskilfulness of the miners, was the foul air which accumulated at the farther end of the excavation: many times it was necessary to withdraw the men for some hours to allow it to clear away. At noon on September 29 the miners declared that they had reached the foundations of the wall, and this seemed correct enough, for they had come to a course of large rough blocks of stone, extending laterally for as far as could be probed. It is probable, however, that the masonry was really the remains of some old advanced turret or outwork, projecting in front of the modern _enceinte_. For when the end of the mine was packed with twelve barrels, containing 90 lb. of powder each, well tamped, and fired at midnight, the explosion brought down many stones from the front of the wall, but did not affect the earth of the rampart, which remained standing perpendicular behind it. There seemed, however, to be places, at the points where the broken facing joined the intact part of the wall, where men might scramble up. Accordingly the storming-column of 300 volunteers who had been waiting for the explosion, was let loose, under cover of a strong musketry fire from the trenches. A sergeant and four men went straight for one of the accessible points, mounted, and were cast down again, three of them wounded. But the main body of the forlorn hope and its officer went a little farther along the wall, reached a section that was wholly impracticable for climbing, and ran back to the trenches to report that the defences were uninjured. The supports followed their example. The loss, therefore, was small--only 29 killed and wounded--but the moral effect of the repulse was very bad. The men, for the most part, made up their minds that they had been sent to a hopeless and impossible task by the errors of an incompetent staff. The engineers declared that the stormers had not done their best, or made any serious attempt to approach the wall.