The siege work was unexpectedly difficult. The inhabitants of the Loire country were skilled artisans, trained in mines and iron works. The walls, built of alternate layers of stone and timber, were forty feet in thickness, and could neither be burnt nor driven in with the ram. The town could be taken only with the help of an agger--a bank of turf and fagots raised against the wall of sufficient height to overtop the fortifications. The weather was cold and wet, but the legions worked with such a will that in twenty-five days they had raised their bank at last, a hundred yards in width and eighty feet high. As the work drew near its end Caesar himself lay out all night among the men, encouraging them. One morning at daybreak he observed that the agger was smoking. The ingenious Gauls had undermined it and set it on fire. At the same moment they appeared along the walls with pitch-balls, torches, fagots, which they hurled in to feed the flames. There was an instant of confusion, but Caesar uniformly had two legions under arms while the rest were working. The Gauls fought with a courage which called out his warm admiration. He watched them at the points of greatest danger falling under the shots from the scorpions, and others stepping undaunted into their places to fall in the same way. Their valor was unavailing. They were driven in, and the flames were extinguished; the agger was level with the walls, and defence was no longer possible. The garrison intended to slip away at night through the ruins to join their friends outside. The wailing of the women was heard in the Roman camp, and escape was made impossible. The morning after, in a tempest of rain and wind, the place was stormed. The legionaries, excited by the remembrance of Gien and the long resistance, slew every human being that they found, men, women, and children all alike. Out of forty thousand who were within the walls, eight hundred only, that had fled at the first sound of the attack, made their way to the camp of Vercingetorix. Undismayed by the calamity, Vercingetorix made use of it to sustain the determination of his followers. He pointed out to them that he had himself opposed the defence. The Romans had defeated them, not by superior courage, but by superior science. The heart of the whole nation was united to force the Romans out of Gaul, and they had only to persevere in a course of action where science would be useless, to be sure of success in the end. He fell back upon his own country, taking special care of the poor creatures who had escaped from the carnage; and the effect of the storming of Bourges was to make the national enthusiasm hotter and fiercer than before.