southward. Then he returned to the pilot-house,
turned on the electric light once more, and glanced at the barometer.
It registered a height of nearly six thousand feet above the sea-level.
This seemed to satisfy the professor; for he opened a valve which
admitted air into the hull, leaving it open until the mercury ceased to
fall in the tube. Then he drew from his pocket a paper which he had
obtained from Mildmay a few hours before, carefully studied for a few
moments the instructions written thereon, and, refolding the paper,
began to manipulate certain of the levers and valves by which he was
surrounded. As he did so a gentle, scarcely perceptible thrill stirred
the gigantic structure which bore him--a humming sound, low at first,
but rapidly increasing in intensity, arose and came floating in through
the pilot-house windows--all of which the professor thereupon closed--
and, seizing the tiller, the lone watcher thrust it gently over, fixing
his gaze meanwhile upon the illuminated compass card of the binnacle.
Presently a certain point on the compass card floated round opposite the
"lubber's mark," whereupon the professor pulled toward him a small lever
upon which he had laid his hand, and two slender steel arms forthwith
slid in through a slit in the side of the compass bowl, one on each side
of a slender needle that projected up through the edge of the compass
card. This ingenious piece of mechanism at once caused the ship to
become self-steering. Then the professor gave three or four turns to a
wheel which controlled the valve admitting vapour to the engine,
throwing the valve wide open, whereupon the humming sound suddenly rose
to a loud and rather high, but pleasing, note as the huge propeller
whirled round at its full speed of one thousand revolutions per minute.
At the same moment the professor noted the exact time by a clock that
formed a portion of the complicated furniture of the pilot-house, and
then, seating himself in a comfortable deck chair, he proceeded to make
certain calculations upon a leaf of a notebook which he drew from his
pocket. At the expiration of a period of twenty minutes the professor
threw the self-steering apparatus out of gear for a moment, altered the
course a trifle to the eastward, threw the self-steering apparatus into
gear again, and waited another twenty minutes, when the same process was
repeated a second time, and so on, a slight alteration of the ship's
course being effec