It was indeed an eerie spot. A thick fringe of thorny shrubs grew along the edge of the cliff; at intervals yawned deep fissures, across which the wise little Arabian ponies stepped gingerly; and above, outlined in intense black against the dark sky, were numerous peaks and pinnacles and castellated summits, such as the Arabs love to people with all manner of genii and evil spirits of the waste and silent wilderness. It was a spot likely to be infested with robbers, and Yusuf and his guide waited in some trepidation while considering what to do. [Illustration: "Hold!" cried a voice from the air above.--See page 34.] Presently a dull trampling sounded in the distance. It came nearer and nearer, and the two lone wanderers on the cliff scarcely dared to breathe. The tread of camels was soon discernible, the "Ikh! Ikh!" (the sound used to make camels kneel) of the camel-drivers rising from the dark pass below to the ears of the men above. Apparently the party was about to make a halt in the dark basin; and should it prove to be a band of hill-robbers, Yusuf and his companion were in a precarious position, for the slightest sound made by them or their ponies would probably prove the signal for an onslaught; but by patting and quieting the animals, they managed to keep their restlessness in check and so waited, scarcely knowing what to do next. Ere ten minutes had elapsed, however, the tread of camels was again heard, and another party came in from the opposite direction, halting at the other end of the ravine. A call was sounded and at once answered by the body immediately below. The new-comers advanced, and mutual recognitions seemed to take place, although Yusuf could distinguish neither the voices nor the words. The parties were, in reality, those of Mohammed and the emissaries of Medina, who at once opened negotiations. After the salutations were over, they extended to Mohammed a formal invitation to Medina. "We will receive you as a confederate, obey you as a leader, and defend you to the last extremity, even as we defend our wives and children," said the spokesman. "For your gracious invitation accept my most hearty thanks," said Mohammed. "My work is not yet ended in Mecca, yet ere long I hope to pay at least a visit to you, O believers of Medina." "But," said the leader, "if you are recalled to your own district you will not forsake us?" "All things," replied Mohammed, "are now common between us. Your blood is my blood. Your ruin is my ruin. We are bound to each other by the ties of honor and interest. I am your friend and the enemy of your foes." He then chose twelve of the men to be the especial heralds of his faith, and all, placing their hands in his, swore fealty to him in life and in death. "If we are killed in your service, what shall be our reward?" asked one of the number. "Paradise!" cried the prophet. "Vales of eternal rest and felicity, odors of sweet spices on the air, blessed spirits to--"