Rejoicing that he had kept the second machine-gun in reserve, Burnet sent Jackson to fetch it from its shelter behind a pile of stones at the extreme left of the position. The shell that had ruined the first had found it by accident; another had exploded in the trench and killed or wounded several of the Arabs; but the Turks had now shortened their range and were dropping their shells many yards nearer the shore. The incident, however, was very disquieting. Luck might favour the enemy again, or the position of the second machine-gun might be more quickly discovered when it came into action, and it was the last reserve. Moreover, the casualties suffered in the trench, more serious than any that the Arabs had hitherto experienced, had had a manifestly depressing effect on the rest of the garrison. Burnet felt a racking anxiety as to their steadiness when the next attack should come. He was standing beside Jackson, who had just set up the machine-gun, when the man suddenly swung round, exclaiming: "Hear that hum, sir?" The bursting of a shell drowned all other sounds, but when the rumbling echoes had ceased, Burnet caught a faint drone far away. He scanned the sky all around; for about a minute nothing was to be seen; but between the shots the humming was clearly audible, growing louder continually. An aeroplane was approaching: was it friend or foe? At last a speck appeared in the eastern sky, growing rapidly larger. It had evidently been seen by the Turks, for the bombardment suddenly ceased: they too, no doubt, were asking themselves the same question. As it drew nearer to the island, the aeroplane rose higher, and presently the prolonged crackle of rifle fire from the Turkish position proclaimed that they had recognised it as a British machine. Hope surged in Burnet's breast. The eyes of all the garrison were fixed on the aeroplane. It flew high over the island, wheeled round, passed directly over the trench, the disdainful target of innumerable Turkish bullets, then soared away northward. A few moments later two deafening explosions in quick succession shook the air, and two columns of smoke rose in the neighbourhood of the northern end of the causeway. The machine again turned, swept away to the east, and was soon out of sight. Before it disappeared, an Arab ran up to Burnet, and handed him an object which he declared had fallen from the sky as the aeroplane passed over, and struck the ground near him. Tearing off the canvas cover of the missile, Burnet found a small shell case, within which was a slip of paper. With leaping heart he read the message. "A flying column of horse is advancing up the Euphrates, and should make contact with you to-morrow morning. We are opening the ball. Carry on."