It was a beautifully fine, clear, starlit night, without the faintest suspicion of a cloud anywhere in the soft, velvety blue-black dome of the sky; and presently, when the professor's eyes had grown accustomed to the dim, mysterious radiance of the twinkling constellations, he was able to see the landscape steadily unfolding around him like a map, in a rapidly widening circle, as the great ship steadily attained an ever-increasing altitude in the breathless atmosphere. For some ten minutes the scientist remained thoughtfully leaning upon the rail, watching the noble expanse of park beneath him dwindle into a mere dark, insignificant blot upon the face of the country, dotted here and there with feebly twinkling lights, until the sleeping waters of the Channel came into view to the 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