ounted the
searchlight. They've ripped everything out. Up ahead, one turn to the
right, then a quarter mile, then a turn toward the crater. That runs
straight for a mile, but there's a field gun at the bottom of the
volcano. We'll be safe when we're on that last stretch."

* * * * *

Ahead of them the rifles of the two who ran in advance crashed out in
a fury of fire as a green glow appeared. But this time the flame did
not die; and Rawson, staring with hot, wide-opened eyes, saw that the
ribbon of green swept transversely across the tunnel.

He could hardly stand when he came to a stop. Beside him Loah was
swaying with weariness. The walls echoed only the hoarse, panting
breath of the men. Then they crept slowly forward, where the passage
went steadily up. Loah's light was out; she had slipped the cap on the
torch at the first sight of that green.

They stopped but ten feet short of the deadly blaze. From a narrow
rift in the left wall it streamed outward, the rock at the edges of
that crack turning to red at its touch. It beat upon the opposite
wall, where already the stone was melting to throw over them a white
glare and the glow of heat. And, like a shimmering, silken barrier,
whose touch could mean only instant death, it reached across the wide
tunnel at the height of a man's waist and moved slowly up and down.
The heaviest armor plate ever rolled could have formed no more
impenetrable a barrier.

"And we almost made it," said Smithy slowly. "Look, beyond
there--another hundred feet. There's the bend in the tunnel, a sharp
turn--and we almost got around!"

Rawson reached for Loah's light. In the wall where the flame was
striking, only a dozen steps back, he had seen another dark mouth, a
ragged crack in the rock. He sprang to the entrance; it might be there
was another way around. His first glance told the story, for he saw
the walls draw together again not a hundred feet off.

"A blind alley," he groaned.

* * * * *

One of the two who had been their advance guard snapped his rifle to
his shoulder. He was aiming at the glowing crack where the green light
was issuing.

"A ricochet," he growled. "It may go on in and mess 'em up." But there
was no whine of a glancing bullet that followed his shot; the
softened wall had cushioned the impact.

Another man sprang beside him. He was shouting at the top of his voice
while one hand reached into a