The Kalmucks did not yet perceive the real object which Bob had in view. After running a short distance, they halted again, unable to decide whether it was safer to advance or retreat. When they saw the aeroplane soaring towards them from the northward, they broke apart, each man striving to find some crevice or nook among the rocks where he might shelter himself. All believed that the Englishman’s purpose was slaughter. But when another bomb was dropped on their southward side, not near enough to do them harm, some of them, as they ran, began to suspect the meaning of the device. For three or four miles they were thus driven down the track. Wherever the gorge was wide enough, Bob wheeled backwards and forwards across it in their rear, swooping down whenever he saw them lagging, with the result that they did not wait for another bomb, but hurried along like a flock of frightened sheep. Once or twice they took shots at the aeroplane, but gave it up when it was patent that their marksmanship was unequal to the feat of hitting the flying target. And all the time the Pathans marched steadily behind them, much amused at the sahib’s method of shepherding, but a little chagrined because they were not allowed to assist. Meanwhile Bob had been thinking out his further proceedings. He must not let the Kalmucks draw too close to the mine. Lawrence could not arrive yet for several hours; it was important that he should come safely home without a collision with the enemy. When, therefore, they had arrived within about two miles of the mine, he decided that it was time to arrest their course. They could no longer be in doubt about the meaning of his signals hitherto--he would give them another. Flying ahead, then wheeling round, he dropped a tin, this time in front of them. At the explosion they halted, and after a brief consultation began to move on. Another bomb, falling in front again, but now a little closer, conveyed its warning; like fog signals on a railway-line, these explosions plainly indicated that the track was not clear. They halted again, and posted themselves behind rocks, facing up-stream, to guard against attack by the Pathans.