which somehow
fired them with his own emotion: "Gor has cut it loose! Water,
millions of tons of it! The Zone of Fire--steam!..." He threw himself
flat on the floor as close to the hot mouth of the cave as he dared
go, and the green flame of his weapon ripped outward and up as he
aimed it.

From the passage, where it sloped downward toward the source of the
heat ray, the sound of shrill, whistling voices had swelled louder.
The whole tunnel now glowed green from the flames of an advancing
horde. They were bringing their ray projector with them, Rawson knew,
not that its beam was visible, but the white, dazzling glow from the
end wall where the tunnel turned was still there.

"Shoot above me!" Rawson shouted. "Don't stick your guns out into that
ray, but aim as straight down the tunnel as you can. Keep 'em busy.
Keep 'em from coming too close."

Above his head he heard the beginning of rifle fire as the men crowded
close to aim at the opposite wall at as flat an angle as they could.
The air grew shrill with the sound of ricochets as the bullets
glanced, but still the enemy came on, as their screeching voices told.

His own weapon was aimed up above. The roof of the tunnel was rough
and broken. He directed the flame against the top of a great black
granite block. In one place it was fractured. If he could cut it off
above, make it fall to the steeply slanting floor.... He worked the
full force of the blast methodically along the line he had chosen.

* * * * *

The air of the tunnel had been blowing gently, but now it came in
sharp gusts that whipped in through the mouth of the cave, while it
brought an unending growl and roar like distant gunfire from deep
within the earth. The breeze had swelled to a steady blast when the
rock crashed down.

"But that's no use," Culver had shouted, when the deafening sound of
its fall had ceased. "They'll melt it in a second with their ray."
Even as he spoke the great mass of granite softened and rolled
downward as the enemy shot their ray on its lower side. The heat of it
struck blastingly into the entrance to their retreat, yet still Rawson
kept on, sawing doggedly with the weapon of flame at other great
blocks above.

Now that distant thunder grew hugely in volume, and again the rocks
trembled beneath them. The wind in the tunnel grew suddenly to a wild
blast. It brought to them from a thousand other passages, the shrill,
demoniac shrieking o