bag that hung at his waist. "Get back,
everyone," he said. "If I miss...." He did not finish the sentence,
but pulled the pin from a hand grenade, then took careful aim and
threw.

It went high--thrown there purposely; he had not dared aim it into the
flame. But it struck the crevice fairly, and they heard it rattle on
inside. The next instant brought the crack and roar of its explosion.

Like a winking signal light the green barrier vanished. Where it had
been was only blackness and the dying glow of molten rock. Then, a
hundred feet beyond, up close to the roof, the bend of the tunnel
turned red; it seemed bursting into flame. Far back of them, down the
long sloping way where they had come, shrill voices were
screaming--and still there was no green flame to account for that
tunnel end flaming red.

Rawson stood motionless. Loah, and the others beside him, seemed
likewise petrified, until the voice of Culver jarred them into action.

"The ray!" he shouted. "It's the heat ray, damn them! Quick, jump into
that cave!"

* * * * *

They had all retreated through fear of the grenade; they were opposite
the black place into which Rawson had looked. Loah was close beside
Dean; he threw her with all his strength into the black mouth of the
cave, then he was one of a crowding, stumbling mass of men who
followed after, and their going was lighted by a terrible torch of
flame.

One man had stood apart from the others, farther across the wide
corridor. His khaki-clad body flashed suddenly to incandescence, then
fell to the floor. And inside the cave, where the walls came abruptly
together to cut off any further retreat, Colonel Culver spoke softly.

"One more gone," he said. "That was Oakley. Well, he never knew what
it was that hit him--and it looks as if we'll all get the same."

Through it all, Rawson had clung to his flame-thrower; unconsciously
his hand had held fast to the bent handle of the cylindrical weapon.
Now he set it down slowly upon the floor, then straightened his aching
body laboriously.

Loah's light was still gleaming. He saw her eyes searching for his,
half in terror, half in wonderment. Strange men with strange
thundering weapons--he knew she was wondering if they still dared
hope, wondering if these warriors of Rawson's race might be able to
work further magic.

Dean put one arm tenderly about her and drew her close and his other
hand came to rest upon Smithy's sho