He walked swiftly over to the speaking-tube which communicated with the condenser room and blew sharply into it.
"Let her go, Gallagher!" he directed.
"My God!" ejaculated Bennie. "Wait a second, can't you?"
But it was too late. He grabbed the rail, trembling. A humming sound filled the air, and the gyroscopes slowly began to revolve. He looked up through the window at the tractor, from which shot streaks of pale vapour with a noise like escaping steam. Somehow it seemed alive.
The Ring was throbbing as if it, too, was impregnated with life. The discharge of the tractor had risen to a muffled roar. Shaking all over, Bennie crossed to the inside window and looked across the inner space of the Ring. As yet the yellow glow of the discharge was scarcely visible, but the steel sides of the Ring danced and quivered, undulating in waves, and, as the intensity of the blast increased and the turbine commenced to revolve, everything outside went suddenly blurred and indistinct.
Dropping to his knees, Bennie looked down through the observation window in the floor. A blinding cloud of yellow dust was driving out and away from the base of the landing stage in the form of a gigantic ring. The earth at their feet was hidden in whirls of vapour; and ripples of light and shade chased each other outward in all directions, like shadows on the bottom of a sandy pond rippled by a breeze. It made him dizzy to look down there, and he arose from the window. Burke stood grimly at the control, unmindful of his associate. Bennie crossed to the other side, and as he passed the gyroscopes, the air from the swiftly spinning discs blew back his hair. He could see nothing through the tumult that roared down through the centre of the Ring, like a Niagara of hot steam shot through with a pale yellow phosphorescent light. The floor quivered under his feet, and ominous creaking and snapping sounds reverberated through the outer shell, as the steel girders of the landing stage were gradually relieved of its weight. Just as it seemed to him that everything was going to pieces, suddenly there was silence, save for the purr of the machinery, and Bennie felt his knees sink under him.
"We're off!" cried Burke. "Watch out!"
The floor swayed as the Ring, lifted by the tractor, swung to and fro like a pendulum. Bennie threw himself upon his stomach. The earth was dropping away from them like a stone. He felt a sickening sensation.
"Two thousand feet already," gasped Burke. "The atmospheric valve is set for five thousand. I'll make it ten! It will give us more room to recover in—if anything—goes wrong!"
He gave the knob another half turn and laid his hand lightly on the lever which controlled the movements of the tractor. Bennie, flattened against the window, gazed below. The great dust ring showed indistinctly through a blue haze no longer directly beneath them, but a quarter of a mile to the north. Evidently they were not rising vertically.