ch depends on the
atmospheric valve, and how much on me. Things may happen quickly. If we
turn over we're done for."

He held out his hand to Bennie, who gripped it tremulously.

"Well," remarked the aviator, tossing away his cigarette, "we might as
well die now as any time!"

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 sin