* * * * * The professor quivered with suppressed excitement as he followed Robert down the flight of steps leading to the outer manhole through which they had entered. At last he was about to know beyond doubt whether the remarkable claims made by his guide had any foundation. If they had, a new era would be unfolded. Again his common sense reacted against hope, blasting his short-lived credulity. That either this boy or his father should have mastered the problem of the fifth dimension after experts of centuries had failed, seemed unbelievable. And yet-- In the deepening twilight the _Sphere_ seemed to loom above them larger than ever. Its lighted portholes, contrasting strangely with its shadowy bulk, gave it a weird, fantastic, almost unearthly aspect. “The _Sphere_ is now in almost perfect equilibrium from every direction,” Robert explained, pride creeping into his voice unconsciously. He indicated two iron rungs near the bottom of the _Sphere_. “If you will take hold here, you will be able to move it in any direction without effort. Softly though--keep a firm hold upon it.” Doubting still, Professor Palmer grasped the rungs, fully expecting to find the vast bulk an immovable weight. To his intense surprize it rose from the floor as if it were an air-filled balloon! He had exerted himself not the slightest bit. The _Sphere_ had simply risen at his first slight lift, and had continued to rise until a slight tug upon his arm stopped it. He extended his right arm, still gripping one rung. The _Sphere_ followed easily, its only resistance apparently that of the atmosphere surrounding it. “Now release it,” suggested Robert. The astonished professor did so, half expecting to see it crash to the floor. But nothing of the sort occurred. For several seconds the giant ball continued to rise very slowly, like a sluggish soap-bubble. Doubtless he had unwittingly allowed his hand to waver slightly when releasing it. Then very, very slowly the _Sphere_ began to descend, finally settling softly and with scarcely a sound. Though it had been but a few feet above the floor, it required fully a minute to come to rest. One noticeable feature was its vertical stability. It neither rolled in its descent nor wobbled in settling, but simply came down with a paradoxical combination of majestic ponderance and zephyrlike softness. “Remarkable!” ejaculated the professor, feeling the inadequacy of the word when applied to this marvelous achievement. “The rigid stability,” Robert explained, “is automatically controlled by a delicate device attached to the central upright gyroscope.” “I was under the impression that the entire apparatus was unaffected by gravity.”