He kicked the door open and there was a stuttering crash as the four automatic pistols simultaneously burst into practically continuous flame--a crash obliterated by an overwhelming concussion of sound as the X-plosive shells, sweeping the entire roof with a rapidly-opening fan of death, struck their marks and exploded. Well it was for the little group of wanderers that the two men in the door were past masters in the art of handling their weapons; well it was that they had in their tiny pistol-bullets the explosive force of hundreds of giant shells! For rank upon rank of soldiery were massed upon the roof; rapid-fire cannon, terrible engines of destruction, were pointing toward the elevators and toward the main stairways and approaches. But so rapid and fierce was the attack, that even those trained gunners had no time to point their guns. The battle lasted little more than a second, being over before either Crane or Dunark could fire a shot, and silence again reigned even while broken and shattered remnants of the guns and fragments of the metal and stone of the dock were still falling to the ground through a fine mist of what had once been men. Assured by a rapid glance that not a single Mardonalian remained upon the dock, Seaton turned back to the others. "Make it snappy, bunch! This is going to be a mighty unhealthy spot for us in a few minutes." Dorothy threw her arms around his neck in relief. With one arm about her, he hastily led the way across the dock toward the Skylark, choosing the path with care because of the yawning holes blown into the structure by the terrific force of the explosions. The Skylark was still in place, held immovable by the attractor, but what a sight she was! Her crystal windows were shattered; her mighty plates of four-foot Norwegian armor were bent and cracked and twisted; two of her doors, warped and battered, hung awry from their broken hinges. Not a shell had struck her: all this damage had been done by flying fragments of the guns and of the dock itself; and Seaton and Crane, who had developed the new explosive, stood aghast at its awful power. They hastily climbed into the vessel, and Seaton assured himself that the controls were uninjured. "I hear battleships," Dunark said. "Is it permitted that I operate one of your machine guns?"