He mentioned it to Rejeb, who received it with a torrent of joyous ejaculations. There was no time to be lost. The chief told off a man to go on foot half a mile along the bank of the wady, to give warning of the enemy's approach. The course of the channel was almost perfectly straight, and horsemen riding along the embankment could be seen from a great distance. Then he selected twenty men, and placed them at Burnet's orders. Burnet took them down to the brink of the wady, chose a spot favourable to his design about half-way through the ruins, and instructed the men to build a dam with the material that lay close to their hands. The channel was shallow, and only about forty feet wide. The men formed two queues, and masses of brick and stone were passed from hand to hand and dumped in the middle. Working with interest and hearty good-will, within an hour the Arabs had raised that obstacle almost to the surface, and in the muddy water it was scarcely visible, even from the bank. Much less was it likely to be seen from the deck of the moving launch, the crew of which would not suspect that the channel they had already navigated safely could hold any danger for them. Having completed the dam, the men returned to their former posts. No change in the general plan was necessitated: indeed, the sudden stoppage of the launch would tend to further it, for it would add one more element to the confusion. It was now only a question of waiting. The Arabs sat their horses in stolid patience, scarcely moving or speaking. Burnet was more restless. He would have liked to steal along the bank of the wady, and watch the stages in the enemy's progress; but he contained himself, and tried to emulate the stillness of his friend the chief. Three hours passed: it was almost midday when the Arab scout came running back with the news that the enemy were in sight. Soon afterwards the sound of the propeller was heard, and then, peeping through the reeds, the watchers saw the horsemen riding two by two at a walking pace along the embankment, and the aeroplane, its wings extending over the banks on either side, as it were floating on the stream. There was now some order in the troopers' march. Three couples rode ahead as an advance guard: after an interval came the two officers riding abreast, and behind them the remainder of the party. Burnet suggested that the advance guard should be allowed to pass, fire being reserved until the main body was half-way through the ruins and unable to escape without fighting. It was impossible now to send a messenger with orders to the men on the north bank, but this gave Rejeb no concern: "My warriors will know what to do," he said, with a firm air of confidence.