ike, to its mark. With clenched teeth, the
Terrestrian forced the whirling lifting vanes to the limit of their
power. They bit into the fast thinning air with a muffled whine,
raised the ship by feet that should have been yards.

By sheer will he forced his oxygen-starved faculties to function, and
realized that he had reached the wall. He was drifting downward, the
hole draining the Dome's air was five feet above him, beyond his
reach. The driven vanes were powerless to stem the craft's fall.

One wing-tip scraped interlaced steel, a horizontal girder, part of
the vault's mighty skeleton. Darl crawled along the wing, dragging
with him a sheet of flexible quartzite. The metal foil sagged under
him and slanted downward, trying like some animate thing to rid itself
of the unwonted burden. He clutched the beam, hung by one leg and one
arm as his craft slid out from beneath him. The void below dragged at
him. He put forth a last tremendous spurt of effort.

Two thousand feet below, Jim Holcomb, dizzy and gasping, manipulated
the controls frenziedly, his eyes fastened on the dropping
pressure-gauge. From somewhere outside the tent a dull thud sounded.
"Crashed! Darl's crashed! It's all over!" Hope gone, only the instinct
of duty held him to his post. But the gauge needle quivered, ceased
its steady fall and began a slow rise. Jim stared uncomprehendingly at
the dial, then, as the fact seeped in, staggered to the entrance.
"That's better, a lot better," he exclaimed. "But, damn it, what was
that crash?"

* * * * *

The headquarters tent was at one edge of the circular plain. Jim's
bleary eyes followed the springing arch of a vertical girder, up and
up, to where it curved inward to the space ship landing lock that hung
suspended from the center of the vaulted roof. Within that bulge, at
the very apex, was the little conning-tower, with its peri-telescope,
its arsenal of ray-guns and its huge beam-thrower that was the Dome's
only means of defense against an attack from space. Jim's gaze
flickered down again, wandered across the brown plain, past the long
rows of canvas barracks and the derrick-like shaft-head. Hard by the
further wall a crumpled white heap lay huddled.

"My God! It was his plane!" The burly Earthman sobbed as his ten-foot
leaps carried him toward the wreck.

Darl was his friend as well as Chief, and together they had served the
Interplanetary Trading Association, ITA, for