She seemed to lift from the ground in a convulsive leap and settled back with a crash that smashed every pane of glass and split her stout sides.
At the same instant, there was an ear-splitting roar as if a boiler had exploded and a flash of ruddy flame.
The exploding gas had caught fire—possibly from a spark from the electric radiators as the bag and their supporting framework was ripped apart by the explosion.
Dazed and half stunned, the boys groped about in total darkness; for the explosion had extinguished every light on the ship.
"Boys, where are you?"
It was Frank calling.
"Great heavens, what a sensation!" gasped the professor, half choked by the powerful fumes of the hydrogen gas which filled the air.
Rapidly the others answered to Frank and groped through the darkness toward his voice. Before them was the shattered side of the cabin. Through the gap was the sky. They could see the bright antarctic stars gleaming. Beyond the rent they knew lay freedom, provided the marauders had not molested their aeroplane.
It was the work of a second to stagger through the opening made by the explosion and gain the fresh air, which they inhaled in great mouthfuls. Then began the dash for the aeroplane.
In the wild confusion that reigned following the explosion, their absence, so far as they could perceive, had not been noticed. As Frank had guessed, the two sentries were knocked senseless by the explosion and the fugitives stumbled over their unconscious figures recumbent on the snow.