At the distance of a ten days’ journey from Medina on the road of the pilgrim caravans from Damascus, lies the deserted rock-city of the Themud, where a whole people had hewn their dwellings in the black rock, decorating the entrances with small columns on both sides, and tracing numerous inscriptions on the walls. No European traveller has ever visited this curious spot, for the Bedouins render the neighbourhood insecure, and the pilgrims to the holy cities allow no infidel to accompany them on their journey. How the subterranean city came to be deserted is still a secret of the past; but probably its ruin must be traced back as far as the first or second century of the Christian era, for Mahomet cites it more than once in his Koran as a warning to all true believers. According to the legend the prophet Saleh once came to Themud to convert the idolatrous inhabitants to the belief of the one true God. As a proof of his divine mission they required a miracle to be performed, upon which the prophet, raising his staff, struck the rock, which immediately opened and gave passage to a she-camel with its young. But the obdurate pagans, still persisting in their incredulity, killed the camel, and the young would no doubt have shared its mother’s fate, if it had not speedily retired into the rock whence it had come forth. The sacrilegious crime of the Themud did not long remain unpunished. A dreadful earthquake destroyed them to the last man, and ever since the place is cursed. When the caravan passes by, the pilgrims raise loud shouts and hurry along as fast as they can, fearful of their dromedaries becoming shy from the wailings of the young camel, which is still supposed to exist in the rock. CHAPTER XXII. TUNNELS. Subterranean London—The Mont Cenis Tunnel—Its Length—Ingenious Boring Apparatus—The Grotto of the Pausilippo—The Tomb of Virgil. The most renowned subterranean works of previous ages are generally of a religious character, as they have been executed to serve either as resting-places for the dead, or as temples in which gods or saints were worshipped. Thus the rock-tombs of the Egyptian Pharaohs and the sacred grottoes of India still bear witness to the feelings which conceived and realised the idea of these stupendous excavations.