knives at Jack
and Mark and the two helpers from the airship.

"There are the boys!" cried Andy, trying to break away from those who
held him.

"An' Tom an' Bill is there likewise!" exclaimed Washington, who had
caught a glimpse of the two helpers. "De heathen am goin' to kill 'um!"

"We're here, Jack!" sung out the hunter. "Make the best fight you can,
for we are in terrible hands. The poor professor is done for, I guess,
and we'll soon be, too!"

His voice rang out high above the shouts and yells of the natives, who
were now in a dense circle about the two boys and their companions.

"We haven't anything to fight with!" called back Mark.

"Well, I have!" yelled Andy.

With a quick motion he snatched his arms from the encircling ones of his
captors. His fists went back. There were two quick, sharp blows, and two
of the Esquimaux who were guarding the old hunter toppled backward.

With suddenness that was startling Andy drew a brace of revolvers from
his inner pockets. He leveled them at the mass of white figures in front
of him, on whose fierce faces the colored lights gleamed and flickered.

Andy's fingers trembled on the triggers. He was about to fire.

"Lay low, boys!" he called to the _Monarch's_ crew. "I'll get rid of a
few of these savages before I go!"

"No shoot! No shoot!" screamed Dirola.

She darted from her place, broke through the circle of natives, and
rushed up to where Andy stood with leveled weapons.

"No shoot! Me save!" she cried.

She was all but too late. Andy's fingers had crooked on the triggers,
but Dirola pushed his arms upward, and when the two reports rang out the
bullets struck the icy roof of the cavern.

In the confined space the shots sounded almost like thunder. A silence
that was startling in its suddenness fell as the echoes of the reports
died away. Dirola ran toward the altar. She grasped the arms of the two
big Esquimaux, who had taken Professor Henderson from the litter with
the intention of sacrificing the old inventor.

She cried out one word in a strange tongue.

The men stopped as though she had struck them. Then, with a dramatic
gesture, she mounted to the top step of the altar.

A chorus of cries greeted her. She seemed to pay no heed. Silent and
straight she stood there on the steps of ice, her figure in dark relief
against the background of flickering lights.

The next instant Dirola, with a motion so quick the eye could scarcely
follow, slipped off