"They’ll have the range in a few minutes," said Burton. "I want you and your friend to carry Captain Enderby out along the track yonder, towards where the prisoners are. Take your daughter, too. When you come back, go down into the cellar and relight the train; it must have gone out. They will smash the tower; the only chance of holding them up is to explode the mine. Make haste, for Heaven’s sake!" Marco summoned Nuta and Milosh from the roof. They lifted Enderby, and were half-way down the stairs with him when the Bulgarian gunners made their first hit. A shell carried away a corner of the parapet. The tower shook under the explosion, and the falling masonry plunged into the enclosure, raising a dense cloud of dust. Burton trembled for the safety of his friends, but his thoughts were taken from them by a renewed movement among the enemy. Immediately after the crash, the men concealed in the bushes sprang out, and dashed forward with a cheer. They would have been wiser to wait. Burton saw them indistinctly through the dust, but he had the range to a yard, and again they melted away under his withering fire. Shells were now bursting around the tower. There was another crash above; fragments of stone fell into the room, striking Burton in many places. It was a moment of racking anxiety. He dared not leave the gun until the track had been destroyed, yet the tower might crumple down upon him. His ammunition was running short--would Marco get back in time? Even if he relit the train, would the flame reach the explosives? And at that crisis he nerved himself for what must be regarded as a supreme act of self-sacrifice. If all else failed, at the last moment he must go himself into the cellar, and fire into the charge. Deafened by the explosions that now recurred every few seconds, smothered in dust, struck by fragments of stone, half choked by fumes, he still held his place at the window. The enemy had learnt a lesson. They kept out of sight. Before long the guns would have done their work, and when the tower was in ruins the way would be clear. "They won’t charge again till we’re smashed," he thought. "Now for it!" Taking his rifle, he hurried down the stairs. At the trap-door he halted a moment. He knew the risk he was about to run. His work in the tunnel had been so hurried that the backward force of the explosion could not be wholly checked. He was taking his life in his hands; but it was the last hope. He gathered himself together. His foot was on the first step when he was brought to a halt by a rifle shot below. The next instant he was hurled back by a terrific concussion, and fell, an immense noise dinning in his ears. For a moment he lay dazed. "Marco must have done it!" he said to himself as he staggered to his feet.