Professor Palmer now divided his time between frequent corrections in the Sphere’s wavering course toward Mars, and the writing of the log.

“Who knows,” he remarked resignedly to his companions, “some other more successful adventurers may attempt this venture some time. There is just a chance in a billion that they may find the Sphere and this document; or the Sphere may finally gravitate back to the earth.”

Almost constantly he watched and guided the Sphere on its intricate course, insisting upon doing the major part of this difficult task, which only his expert knowledge of the heavens made possible to such a degree of accuracy. But even he was beginning to find it almost impossible to keep the Sphere on its true course, as it continued to swing more and more widely from its former stability. Loss of sleep and the terrific strain were beginning to tell upon his iron constitution. It was clear to all three that theirs was a losing struggle. The professor’s faint hope that they could decrease their distance from Mars sufficiently to establish a substantial stability upon its attraction faded more and more as gradually the little Sphere began to swoop in ever-increasing deviations from its course.

Realizing with sinking heart the hopelessness of the situation, Professor Palmer endeavored to conceal the sureness of their fate from Robert and Taggert. But they sensed it intuitively and each bravely sought to steel himself against the realization of the end.

The thought of conserving their energy by stopping the gyrostats occurred to Robert. For with gravitation virtually equalized from all directions, their operation was scarcely of any assistance at this point.

And then came the thought that caused his heart to halt an instant in its beat. Could it be that both the professor and he overlooked the one possible solution? Was it too late?

“Fool—fool!” he expostulated bitterly as he realized the opportunity that had all but slipped away from them by his failure to think of the solution sooner.

“Robert!” cried Professor Palmer, fearing for his mind. “What is it?”

“Can you hold her to the course steadily for a minute?” Robert almost shouted in his excitement, not having heard the professor’s question.

Professor Palmer suddenly realized with a flash of hope that Robert had thought of a possible way out of their predicament.