Then dimly
came the recollection of Eskimo legends concerning thermal springs
beyond the desolate and unknown reaches of Grant Land.

His mind in an indescribable turmoil, Nelson splashed across a hundred
yards of sodden snow, then shivered on wading knee deep through a pool
of melted ice. Now he stood on the very threshold of that awful
opening, dense clouds of vapor beating warmly against his chilled
features.

His goggles fogged at once, blinding him effectively as, with reason
staggering under the accumulated stress of starvation and the
circumstances of Alden's disappearance, he groped his way a few feet
into the vent. With his left hand he pulled up the glasses from his
sunken, blood-shot eyes.

"It's warm, by God!" he cried in astonishment as the skin exposed by
lifting the goggles came in contact with the air. "Must be some kind
of earth-warmed cave."

* * * * *

Increasingly mystified, he caught up his rifle and strode on down the
passage, at that moment illuminated by the last unearthly rays of the
aurora borealis. A single, dazzling beam played before him like a
powerful searchlight, to light a high vaulted tunnel of basalt rocks
which were distorted by some long-gone convulsion of the earth into a
hundred weird cleavages and faults. For that brief instant he found he
could see perhaps a hundred feet down into a high roofed passage,
along the top of which poured a tremendous stream of billowing,
writhing steam.

"If this doesn't beat all," he murmured; but for all of his
apprehension he did not pause. Those bloody splashes bespeaking
Alden's pressing need urged him on. "Looks like I'm taking a one way
trip into Hell itself. Well, we'll soon see."

Slipping and sliding over an almost impassable array of black rocks
and boulders, Nelson fought his way forward, conscious that with every
stride the air grew damper and warmer. Soon trickles of sweat were
pouring down over his chest, tickling unbearably.

Then all at once the ray of light faded, leaving him immersed in a
blackness equalled only by the gloom of a subterranean vault. He
stopped and, resting his rifle against a nearby invisible rock, threw
back the parka hood and pulled off his gloves. He was amazed to feel
how warm the strong air current was on his hands.

"Beats all," he muttered heavily. "I wonder where they've taken
Alden?"

* * * * *

Meanwhile his hands groped through