with electricity. His clothing stiffened and
crackled. His hair crawled on his head. He could see the faint
discharges of sparks from his companions.

Whether it was the effect of the charged air, or the reaction from the
nervous strain of the past hours, Mel Gray began to be afraid.

Weary to exhaustion, they struggled on against the burning wind. And
then they blundered out into a cave, huge as a cathedral, lighted by a
queer, uncertain bluish light.

Gray caught the sharp smell of ozone. His whole body was tingling with
electric tension. The bluish light seemed to be in indeterminate lumps
scattered over the rocky floor. The rush of the wind under that
tremendous vault was terrifying.

They stopped, Gray keeping to the background. Now was the time to evade
his unconscious helpers. The moment they reached daylight, he'd be
discovered.

Soft-footed as a cat, he was already hidden among the heavy shadows of
the fluted walls when, he heard the voices.

They came from off to the right, a confused shout of men under fearful
strain, growing louder and louder, underscored with the tramp of
footsteps. Lights blazed suddenly in the cathedral dark, and from the
mouth of a great tunnel some hundred yards away, the men of the Project
poured into the cave.

And then, sharp and high and unexpected, a man screamed.

* * * * *

The lumps of blue light were moving. And a man had died. He lay on the
rock, his flesh blackened jelly, with a rope of glowing light running
from the metal of his gun butt to the metal buttons on his cap.

All across the vast floor of that cavern the slow, eerie ripple of
motion grew. The scattered lumps melted and flowed together, converging
in wavelets of blue flame upon the men.

The answer came to Gray. Those things were some form of energy-life,
born of the tremendous electric tensions on Mercury. Like all
electricity, they were attracted to metal.

In a sudden frenzy of motion, he ripped off his metal-framed goggles,
his cap and gun-belt. The Moultons forbade metal because of the danger
of lightning, and his boots were made of rubber, so he felt reasonably
safe, but a tense fear ran in prickling waves across his skin.

Guns began to bark, their feeble thunder all but drowned in the vast
rush of the wind. Bullets struck the oncoming waves of light with no
more effect than the eruption of a shower of sparks. Gray's attention,
somehow, was riveted on Jill, stan