"Fire!" shouted Tempest, stepping back, as the daring bandits, regardless of the danger, started the propellers once more by means of the self-starting knob, within the conning-tower. And the next instant, even as the machine turned and raced for safety, a terrific hail of bullets from the two machine guns swept the _Scorpion_ from stem to stern. One of her machine guns was swept from its mountings, and it is believed that one at least of her crew was wounded, probably by the Colonel’s revolver shots, but as for surrender, the pirates would have none of it, as, apparently unhurt in any vital spot, the _Scorpion_ recrossed the aerodrome, staggering once or twice under the fierce welter of bullets, managed to leave the ground, and sail over the tree tops out of immediate range. "Confound it! She’s absolutely bullet-proof!" shouted the colonel, who was furious at his failure, for his object had been to capture the machine and its crew wholesale, because of its valuable secrets. "We shall see no more of her!" exclaimed Captain Hooper. "Just wait a moment," said the skipper of the air-liner. "She’ll have something to say presently. You don’t know these infernal brigands." The last speaker was right, for a moment later the infuriated Spitzer, sweeping round at a frightful speed, swooped down upon the little hangar, where he presumed the English were in possession, swept the place with a burst of machine gun fire from his remaining gun, then dropped a bomb filled with high explosive right into the middle of the structure; whilst he, himself, was screened by the trees from the enemy’s fire. The roar of the explosion was deafening, and several trees in the vicinity of the workshop were blown to fragments, whilst the workshop was now a tangled mass of wreckage. It was also burning furiously, and a thick pall of dense smoke already hung over the spot. "The professor!--we must save him!" cried Tempest, who was already limping from a bomb splinter which had pierced his leg. Captain Watson ran to help him, but the two machine gunners, Sharpe and Hooper, stuck to their posts ready for the next attack, which they knew would not be long delayed, for Spitzer, during his last circuit, had marked the position of the two machine gun posts. As the rescuers hastened to the assistance of the prisoners, they came upon Professor Verne, bleeding from the hands and face, dragging the prostrate form of the German from amid the burning wreckage. "Ah, you are wounded?" cried the colonel. "It is nothing," replied the other. "See to the mechanic. I fear he is killed, poor fellow, by his own countrymen." It was so; his mangled form was found buried under the _débris_ of the workshop. The German professor and his rescuer were both helped to safety; then the battle began again. "Here comes the _Scorpion_!" shouted Captain Watson. "Look out there!" and instantly the air resounded with the sharp, short crackle of the air brigand’s gun--