f air that was torn and ripped on projecting
ledges of rock. Mingled with it was the sound of voices that screamed
in terror, and the echo of feet running in mad flight down the tunnel.

The mass of stone, that had been melting under the invisible ray,
cooled to red, then to black. Outside, the tunnel, now a place of
roaring winds, was lighted only by the single flame of Dean's weapon.

"They've gone!" Culver shouted. "The ray's off. Get outside! Now we'll
run for it!" And, with the others, Rawson sprang to his feet and
leaped out into the tunnel which was no longer a place of death.

* * * * *

He heard the sound of their hurrying feet and a voice that cried:
"Look out for the turn--the rock's hot," but he did not look after
them. He was standing squarely, bracing himself in the blast of air,
still directing the flame upon a block that hung stubbornly and would
not let go.

He knew that Loah alone stood near. He heard other feet; someone was
returning. Then Smithy was upon him, almost jarring him from his
careful pose. Smithy was shouting.

"Come back, Dean!" he cried. "Are you crazy? Don't you know they'll be
after us again?"

Rawson sprang as the big rock let go. It, too, crashed deafeningly
upon the floor and rolled sluggishly downward beside the high hummock
of glass that the first rock had become. They bulked hugely in the
passage. They were eight or ten feet high, reaching across from one
wall to the other.

Above them was still a space of four feet; Rawson estimated it
carefully while he looked at the ceiling above. Then he shook off
Smithy's hand that was dragging at him and returned to the attack; for
now, above the top of the barricade he had built, white ribbons of
vapor were streaming. He had to shout to his utmost to make Smith hear
above the shrill shriek of the blast.

"Steam!" he screamed into Smithy's ear. "Live steam! We could never
make it--before we got to the top we'd be cooked to a pulp. I've got
to block it, got to seal it off." A whole section of the ceiling tore
loose as he spoke, and the wind raised its voice like the scream of a
wounded animal--or the cry of an overwhelmed and stricken people--as
it tore through the space that remained.

* * * * *

It whipped the molten drops as they fell and made of them a deadly
rain. Rawson, staring through the clouds of hot steam that now wrapped
him about, called to Smithy to tak