Robert’s next move was to adjust the direction of the disk’s covered face toward the zenith. The gyrostats were revolving smoothly. With bated breath, he again pushed the button which partly bared the disk.
The Sphere gave a slight lurch. This was followed by a sensation like that felt in an elevator rising suddenly. A faint shout from below. With one impulse Robert’s and the professor’s glances swept eagerly through the ports.
There they saw just what they had expected to see; but the actuality affected them curiously. Oddly enough, they had subconsciously expected till the last moment that the Sphere would fail.
The landscape seemed to be dropping from under them. Even the horizon was receding alarmingly.
Robert’s hand shot out to the control board, closing the disk’s surface. A slight tremor evidenced the abrupt cessation of the disk’s pull.
“Six thousand feet,” read Professor Palmer from the altimeter.
Robert joined him. A few minutes later it registered seven thousand. They were still rising, but not nearly so rapidly as before. The closing of the disk had checked their speed at once.
“A little more and I’d have boosted her right off the earth,” said Robert, breathlessly. “I’ll have to use the disk more sparingly on ordinary sight-seeing excursions hereafter.”
“You had it opened only to first power, too, hadn’t you?”
“Yes; and without the ‘juice’ turned on. Jove! We didn’t realize how much reserve power of propulsion we had. It’s well that I experimented first with the minimum. And the current almost quadruples the magnetism of mythonite! Phew!”