“Fifty miles southeast of the Pole,” he said at last.  “Shall we attempt to go on or turn back?”

The boys looked at one another.  Bruce read in his companions’ eyes the desire to attempt the return with the dog-team.  At the same time, he realized that the real genius of an explorer lay in his desire to push on.  The Major had that genius.

“As for me,” Bruce said finally, “I never decide anything of great importance until I have slept over it.”

Barney smiled in spite of his anxiety and weariness.

But the Major, seeing the strained expression in the boys’ faces, realized that the ultimatum of Bruce was a good one.

Soon the three companions were snug in their sleeping-bags, dreaming of a land of grass and flowers far, far away.

* * * * *

As soon as the submarine was safely on its course after the glacier incident, Dave, who had not slept for many hours, turned in for “three winks.”  His three winks had stretched on into hours, when he was wakened by a sudden jarring that shook the craft from stem to stern.  He was on his feet in the passage-way at once.

“What happened?” he demanded of a sailor.

“Blamed if I know,” said the other.  He was white as a sheet.

One thing Dave made sure of as he hurried toward the wheel-room; they were drifting under the ice-floor of the ocean.  Was the motor simply dead, or was the propeller gone?  He had but an instant to wait.  There came the purr of the motor, then the sudden sound of racing machinery, which told plainer than words that the worst had happened.

“I think it was a walrus, sir,” said Rainey, who had been in charge of the wheel-room.  “I had just caught sight of a dark blotch gliding by and reached for the power when the racket started.”

“What were you making?” asked Dave quietly.

“Our usual ten knots.”

The compartment they were in was filled with levers and adjusting wheels of all descriptions.  The walls were lined with gauges and dials of many styles and sizes.  A person on entering and taking the operator’s position, might fancy himself in the center of a circle of gears and driving wheels of many automobiles.

Dave glanced at a gauge, then at another.  He touched a wheel, and the hand on the second dial began to drop.  They were now rising.  As a usual thing, they traveled some forty feet below the surface.  Icebergs were scarce in these waters, and the ordinary floe did not lie more than twenty feet below sea-level; still, it was safer lower down.  But now—­now their safety rested in gliding to a point beneath a water channel or hole, and, once they were under it, they must not fail to rise.

“No, not if it takes our conning-tower to do it!” Dave said savagely, as he finished explaining.

They were still drifting through the water at a rather rapid rate, but little by little a speed gauge was falling.  Soon they would be lying motionless beneath the Arctic floe, as helpless as a dead whale; and should no dark water-hole appear before that time came, they were doomed.