“This device is the exception. The _Sphere’s_ weight is neutralized to an absolute minimum by the gyroscopic control, but it was necessary to maintain one point of gravitational contact in order to establish some permanent upright stability; otherwise, the _Sphere_ would revolve at random when in midair.” “Manifestly.” “This device also makes it possible to maintain the observation ports at the ends of the main compartment in any desired direction horizontally. It may surprize you to hear that this device was the last part perfected. My father’s final prostration was largely due to its intricacies. He passed away just as he was about to achieve its perfection.” A slight quaver in Robert’s voice betrayed his grief and his deep regard for his departed parent. Professor Palmer’s eyes kindled sympathetically. “On the contrary,” he replied, “I can readily understand the difficulties encountered.” A silence ensued during which each was busy with his own thoughts. Robert was thinking of the most important feature of all--the propulsion of the _Sphere_, and its control. This principle had been worked out on a small scale, but owing to its prohibitive cost on a larger scale he had been unable to perfect its application to the _Sphere_. Professor Palmer, with his personal resources and backing, could finance it, but even then, Robert estimated, it would tax his total resources heavily. Robert held no illusions on this point, and he was wondering how best to present his plea for financial aid. * * * * * Professor Palmer was trying to visualize the possibilities in the _Sphere_. In it he saw a possibility of proving his own theories regarding the planet Mars, and this brought him round to the very feature on which Robert’s thoughts were concentrated at that moment. “Hm-m,” mused the professor. “And you claim to have worked out a scheme of magnetic propulsion requiring a minimum of internal energy?” Robert drew a full breath and prepared to retrench. “Only on a small scale, professor. I have a miniature model over here, illustrating the practicability of the idea.” He switched on the light over a work-bench, revealing a curious contrivance about five inches high. A dull black rod, terminating in a tiny blunt bell-like device, hung suspended from a universal joint. The whole was supported by a small frame bolted to the table. Examination of the bell-like bulb showed that its larger end was flat, and composed of a dull, whitish metallic substance similar in appearance to aluminum. Its outer surface was a brilliant silver. This bulb seemed of extraordinary weight for so small an object, swinging heavily back to its former position when released, where it came to rest quickly over the center of the disk almost as if bound in that position with a strong, invisible elastic band.