Already they were soaring over the expanse of water. On the horizon the distant Canadian shore was rapidly taking shape. Beneath them several long, slim lake craft could be discerned, crawling at what appeared, from so great a height, to be a snail’s pace. No doubt the _Sphere_ would have presented a much more curious sight to those below had its luminous gray shell been more than a faint speck against the brilliant, cloudless sky. It was at this juncture that Robert’s alert ears detected a subtle change in the hitherto soft whir of the gyrostats. “What is it, Robert?” whispered Professor Palmer, as he observed Robert’s suddenly tense attitude. “Wait!” anxiously. Outside, the muffled roar sounded in strange contrast to the still air within. The bright sunshine streamed across the gray door in mock cheerfulness. A single captive fly buzzed drowzily against a windowpane. These commonplace details registered on Robert’s mind indelibly in those fleeting seconds as he listened with palpitating heart for he knew not what. Taking his cue from Robert, Professor Palmer was listening with equal intensity to the drone of the machinery upon which their lives depended. Even he could now detect the change. The drone was gradually, unmistakably, decreasing in volume. The gyrostats were stopping! Unconsciously they gripped each other’s hands an instant as they realized the seriousness of their plight. Should the gyrostats stop, the _Sphere_ would plunge to its doom! Frantically Robert tortured his mind for a possible solution, or a reason for the unexpected interruption. The altimeter already indicated that they were falling at a steadily increasing speed. The formerly tiny ships below were no longer tiny. The water seemed to be rushing toward them at a terrific rate. Robert remembered afterward a sudden inane conjecture as to how big a splash they would make. It was at this moment his numbed senses returned to him. Cursing himself silently for a rattle-brained idiot, he spun the wheel madly, thus adjusting the vertical position of the disk. To his tortured mind it seemed an eternity before it finally pointed toward the zenith. Their downward rush was noticeably checked, but the lift of the disk was not equal to the weight of the _Sphere_. They continued to fall at a dangerous rate. The altimeter registered but two thousand feet! Fully recovered now from his former temporary inertia, Robert jammed over the switch which connected the disk to the powerful storage batteries. This was the reserve that he had not ventured to utilize before. Thus the lift of the _Sphere_ should have been increased more than four-fold, and its descent checked at once. As the switch swung over, the gyrostats stopped completely. In a flash the explanation of it all occurred to Robert. The batteries were exhausted! 6 The world was rudely shaken from its customary lethargy.