ened goggles.

Frantic questions surged through the captured Earthman's mind. Who was
his captor? From where, and how, had he come to Mercury? Jim, Angus
McDermott, and himself were the only Terrestrians on the planet; of
that he was certain. Only one or two of the reptile-skinned Venusian
laborers had sufficient intelligence to manipulate a space suit, and
they were unquestionably loyal.

This individual was a giant who towered far above Darl's own six feet.
The Mercurian natives--he had seen them when ITA's expedition had
cleaned out the burrows beneath the Dome and sealed them up--were
midgets, the tallest not more than two feet in height. Whatever he
was, why was the stranger trying to destroy the Dome? Apparently
Thomas himself was not to be killed offhand: the jolting journey was
continuing interminably. With enforced patience the Earthman resigned
himself to wait for the next scene in this strange drama.

* * * * *

In the headquarters tent Jim's usual grin was absent as he moved
restlessly among the switches and levers that concentrated control of
all the Dome's complex machinery. "Darl's been gone a devilish long
time," he muttered to himself. "Here it's almost time for shifts to
change and he's not back yet."

A bell clanged, somewhere up in the mass of cables that rose from the
control board. For the next ten minutes Holcomb had no time for worry
as he rapidly manipulated the innumerable wheels and handles in accord
with the vari-colored lights that flickered on a huge ground-glass map
of the sub-Mercurian passages. On the plain outside there was a vast
rustling, a many-voiced twittering and squeaking that was not quite
bird-like in tone. Through the opened tent-flap one could see the
stream of Venusian workers, their work-period ended, pouring out of
the shaft-head and filing between the ordered ranks of others whose
labors were about to begin.

They were queer-looking specimens, these gentle, willing allies of the
Earthmen. Their home planet is a place of ever-clouded skies and
constant torrential rains. And so the Venusians were amphibians,
web-footed, fish-faced, their skin a green covering of horny scales
that shed water and turned the sharp thorns of their native jungles.
When intrepid explorers discovered in the mazes of Mercury's spongy
interior the _surta_ that was so badly needed as a base material for
synthetic food to supply Earth's famine-threatened populatio