fter him thudded the gigantic
lizard, its neck arching up and along the wall to reach him.

A scant five yards ahead of the snapping jaws, Brand reached his goal,
the dome, and clambered over its curved, metal roof away from the
monster's maw.

He stopped to pant for breath and wipe the sweat from his streaming
face. "Thank God it didn't get me," he breathed, looking back at the
bellowing terror that had pursued him. "Wonder why it's there? It's
too ferocious to be tamed and used in any way: it must be kept as a
threat to hold the slaves in hand. It certainly looks well fed...."

He shuddered; then he began to explore the dome of the building for a
means of entrance.

* * * * *

There was no opening in the roof. A solid sheet of reddish metal, like
a titanic half-eggshell, it glittered under him in an unbroken piece.

He crept down its increasingly precipitous edge till he reached a sort
of cornice that formed a jutting circle of stone around it. There he
leaned far over and saw, about ten feet below him, a round opening
like a big port-hole. From it were streaming waves of warm, foul air,
from which he judged it to be a ventilator outlet.

He scrambled over the edge of the cornice, hung at arm's length, and
swung himself down into the opening. And there, perched high up under
the roof, he looked down at an enigmatic, eery scene.

That the structure was indeed a strange sort of power-house was
instantly made evident. But what curious, mysterious, and yet
bewilderingly simple machinery it held!

In the center was a titanic coil of reddish metal formed by a single
cable nearly a yard through. Around this, at the four corners of the
compass, were set coils that were identical in structure but a trifle
smaller. From the smaller coils to the larger streamed, unceasingly,
blue waves of light like lightning bolts.

Along a large arc of the wall was a stone slab set with an endless
array of switches and insulated control-buttons. Gauges and indicators
of all kinds, whose purpose could not even be guessed at, were lined
above and below, all throbbing rhythmically to the leap of the
electric-blue rays between the monster coils.

* * * * *

Almost under Brand's perch a great square beam of metal came through
the building wall from outside, to be split into multitudinous smaller
beams that were hooked up with the bases of the coils. Across from
him, disapp