ere making a quick turn for a
spiral descent. That ought to throw her nearly on her beams' end, and
we'll see how the gyroscope works. That will be a good test. I'll
stand by to correct any fault in the gyroscope."

They were all a little apprehensive as they ranged themselves in line
near one wall of the cabin. The airship tilted slightly as all the
weight came on one side, just as a big excursion steamer lists to
starboard or port when the crowd suddenly rushes all to one rail. But,
on a steamer, deck hand are kept in readiness, with barrels of water,
and these they roll to the opposite rail of the boat, thus preserving
the balance.

Mr. Vardon depended on the gyroscope to perform a like service for the
airship, and to do it automatically.

The aviator waited a few moments before giving the order to make the
sudden rush. Already the apparatus to which was contrasted Lieutenant
Larson's mercury tubes, had acted, and the Abaris, which had dipped,
when all the passengers collected on one side, had now resumed her
level keel again, showing that the gyroscope had worked so far at any
rate.

"Now we'll give her a trial," called Mr. Vardon. "All ready, come over
on the run, and throw her around, Dick!"

On the run they came, and Dick whirled the steering wheel around to the
left, to cause the Abaris to swerve suddenly.

And swerve she did. With a sickening motion she turned as a vessel
rolls in a heavy sea, and, at the same moment there was a dip toward
the earth. The motor which had been humming at high speed went dead on
the instant, and Dick Hamilton's airship plunged downward.

CHAPTER XVI

DICK IS WARNED

"What's the matter?"

"What happened?"

"We're falling!"

"Somebody do something!"

Everyone seemed talking at once, calling out in fear, and looking
wildly about for some escape from what seemed about to be a fatal
accident. For the Abaris was over half a mile high and was shooting
toward the earth at a terrific rate.

"Wait! Quiet, everybody!" called Dick, who had not deserted his post
at the steering wheel. "I'll bring her up. We'll volplane down!
It'll be all right!"

His calmness made his chums feel more secure, and a glance at Mr.
Vardon and his machinist aided in this. For the veteran aviator, after
a quick inspection of the machinery, no longer looked worried.

"What has happened?" asked Innis.

"Our engine stalled, for some unknown reason," answered Mr. Vardon,
quickl