ors were not completely charged.

But, after giving simple operating instructions to the students, Arcot
and Morey went with Stel Felso Theu to his laboratory.

"Here," Stel Felso Theu explained, "is the original apparatus. All these
other machines you see are but replicas of this. How it works, why it
works, even what it does, I am not sure of. Perhaps you will understand
it. The thing is fully charged now, for it is, in part, one of the
defenses of the city. Examine it now, and then I will show its power."

Arcot looked it over in silence, following the great silver leads with
keen interest. Finally he straightened, and returned to the Talsonian.
In a moment Morey joined them.

The Talsonian then threw a switch, and an intense ionization appeared
within the tube, then a minute spot of light was visible within the
sphere of light. The minute spot of radiance is the real secret of the
weapon. The ball of fire around it is merely wasted energy.

"Now I will bring it out of the tube." There were three dials on the
control panel from which he worked, and now he adjusted one of these.
The ball of fire moved steadily toward the glass wall of the tube, and
with a crash the glass exploded inward. It had been highly evacuated.
Instantly the tiny ball of fire about the point of light expanded to a
large globe.

"It is now in the outer air. We make the--thing, in an evacuated glass
tube, but as they are cheap, it is not an expensive procedure. The ball
will last in its present condition for approximately three hours. Feel
the exceedingly intense heat? It is radiating away its vast energy.

"Now here is the point of greatest interest." Again the Talsonian fell
to work on his dials, watching the ball of fire. It seemed far more
brilliant in the air now. It moved, and headed toward a great slab of
steel off to one side of the laboratory. It shifted about until it was
directly over the center of the great slab. The slab rested on a scale
of some sort, and as the ball of fire touched it, the scale showed a
sudden increase in load. The ball sank into the slab of steel, and the
scale showed a steady, enormous load. Evidently the little ball was
pressing its way through as though it were a solid body. In a moment it
was through the steel slab, and out on the other side.

"It will pass through any body with equal ease. It seems to answer only
these controls, and these it answers perfectly, and without difficulty.

"One other thin