But behind all this, and encased as it were in a frame, the landscape rose in a gentle slope to the summit of the thundering mountain. But indications were not wanting of the peril with which the city was threatened. The whole district is volcanic; and a few years before the final catastrophe, an earthquake had shaken Pompeii to its foundations; some of the buildings were much injured. On August 24, A.D. 79, the inhabitants were busily engaged in repairing the damage thus wrought, when suddenly and without any previous warning a vast column of black smoke burst from the overhanging mountain. Rising to a prodigious height in the cloudless summer sky, it then gradually spread out like the head of some mighty Italian pine, hiding the sun, and overshadowing the earth for miles in distance. The darkness grew into profound night, only broken by the blue and sulphurous flashes which darted from the pitchy cloud. Soon the thick rain of thin, light ashes, almost imperceptible to the touch, fell upon the land. Then quickly succeeded shower of small pumice stones and heavier ashes, and emitting stifling eruptic fumes. After a time the sounds of approaching torrent were heard, and soon streaming rivers of dense black mud poured slowly but irresistibly down the mountain sides, and circled through the streets, insidiously creeping into such recesses as even the subtle ashes had failed to penetrate. There was now no place of shelter left. No man could defend himself against this double enemy. It was too late for flight for such as had remained behind. Those who had taken refuge in the innermost parts of the houses, or in the subterranean passages, were closed up forever. Those who sought to flee through the streets were clogged by the small, loose pumice stones, which lay many feet deep, or were entangled and overwhelmed in the mud-streams, or were struck down by the rocks which fell from the heavens. If they escaped these dangers, blinded by the drifting ashes and groping in the dark, not knowing which way to go, they were overcome by the sulphurous vapors, and sinking on the highway were soon buried beneath the volcanic matter. Even many who had gained the open country, at the beginning of the eruption, were overtaken by the darkness and falling cinders, and perished miserably in the field or on the sea-shore, where they had vainly sought the means of flight. In three days the doomed city had disappeared. It lay buried beneath a vast mass of ashes, pumice stone and hardened mud, from twenty to seventy feet deep. Those of its terror-stricken inhabitants who escaped destruction, abandoned forever its desolate site. Years, generations, centuries went by, and the existence of Pompeii--yea, even its very name--had ceased to be remembered. The rich volcanic soil became covered with a profusion of vegetation. Vineyards flourished and houses were built on the site of the buried city.