Reluctantly he withdrew his eyes from the mysterious sphere and looked about the room once more. No, the laboratory was vacant of human occupants. No one was hidden among the benches that were cluttered with beakers and test tubes and stills, or among the dynamos and transformers in the other end of the room.

A confusion of questions beat through Larry's brain.

What danger could be haunting this quiet laboratory? Was this the blood of Agnes Sterling or the scientist who employed her that was now clotting on the floor? What terrific force had crumpled up the revolver? What had become of Agnes and Dr. Whiting? And of whatever had attacked them? Had Agnes called him after the attack, or before?

Despite himself, his attention was drawn back to the little globe spinning so regularly, floating in the air between the pillars of red and violet flame. Floating alone, like a little world in space, without a visible support, it might be held up by magnetic attraction, he thought.

D

A tiny planet!

His mind quickened at the idea, and he half forgot the weird mystery gathering about him. He stepped nearer the sphere. It was curiously like a miniature world. The irregular bluish areas would be seas; the green and the brown spaces land. In some parts, the surface appeared mistily obscured—perhaps, by masses of cloud.

Larry saw an odd-looking lamp, set perhaps ten feet behind the slowly spinning, floating ball, throwing upon it a bright ray of vividly blue light. Half the strange sphere was brilliantly illuminated by it; the rest was in comparative darkness. That blue lamp, it came to Larry, lit the sphere as the sun lights the earth.

"Nonsense!" he muttered. "It's impossible!"

Aroused by the seeming wonder of it, he was drawn nearer the ball. It spun rather slowly, Larry noted, and each rotation consumed several seconds. He could distinguish green patches that might be forests, and thin, silvery lines that looked like rivers, and broad, red-brown areas that must be deserts, and the broad blue stretches that suggested oceans.

"A toy world!" he cried. "A laboratory planet! What an experiment—"

Then his eyes, looking up, caught the glistening, polished lens of a powerful magnifying glass which hung by a black ribbon from a hook on one of the heavy steel beams which 

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