Faintly behind us came shootings, and we knew that Lugur drew close.

Nor anywhere was there sign of Lakla nor her frogmen.
Now we were half-way to the crest; the shell barely crawled and from beneath it came a faint hissing; it quivered, and I knew that its base was no longer held above the glassy surface but rested on it.
"One last chance!" exclaimed Rador.

He pressed upon the control lever and wrenched it from its socket.

Instantly the sparkling ball expanded, whirling with prodigious rapidity and sending a cascade of coruscations into the cylinder.

The shell rose; leaped through the air; the dark crystal split into fragments; the fiery ball dulled; died--but upon the impetus of that last thrust we reached the crest.
Poised there for a moment, I caught a glimpse of the road dropping down the side of an enormous moss-covered, bowl-shaped valley whose sharply curved sides ended abruptly at the base of the towering barrier.
Then down the steep, powerless to guide or to check the shell, we plunged in a meteor rush straight for the annihilating adamantine breasts of the cliffs! Now the quick thinking of Larry's air training came to our aid.