gin of matter itself, Cor said, which lay in the ether
of interstellar space--energy, raw, cosmic--vibrations, rays.

By harnessing and controlling these various rays, his people had been
able to accomplish their seeming miracles--miracles that the people of
earth, too, were beginning to achieve--as in electricity, for
instance, and its further application, radio.

But the people of Vada had long since mastered such simple rays, and
now, in possession of vastly more powerful ones, had the elemental
forces of the universe at their disposal.

* * * * *

The disc was propelled through space by short rays of tremendously
high frequency, up above the ultra-violet. The same rays, directed
downward instead of outward, enabled them to overcome the pull of
gravity when in a planet's influence, as at present. And the escalator
rays, by which they could proceed to and from the disc, were also of
high frequency, as were their invisibility rays.

"But you, Professor, are more interested in low frequency rays, the
long ones down below infra-red," continued Cor. "You have seen our
development of the heat-dynamo principle. It utilizes, I might add,
not only solar radiation but that of the stars as well. There being a
billion and a half of these in the universe, many of them a thousand
times or more as large as your own sun, we naturally have quite an
efficient little heating plant here. It provides us with our weapon of
warfare, as well as keeping us warm. Permit me to demonstrate."

He led the way to a gleaming circle of glass like an inverted
telescope, about a yard in diameter, mounted in the floor.

"Look!" said the dwarf.

Kendrick did so--and there, spread below him, lay the floor of the
desert. His camp, his apparatus, were just as he had left them.

Cor now moved toward the dial.

"Behold!" he said, pulling a lever.

Instantly the scene below was an inferno. Stricken by a blast of
stupendous heat, the whole area went molten, lay quivering like a lake
of lava in the crater of an active volcano.

"Suppose, my dear Professor," smiled the dwarf, strolling back from
the dial, "just suppose, for instance, that instead of the lonely
camp of an obscure scientist, your proud city of New York had been
below there!"

* * * * *

Kendrick shuddered.

Well he knew now the terrible power, the appalling menace of this
strange invader.

"I would prefer not to mak