At once every man was at his task.  The submarine moved slowly toward the water.  There followed a dip, a great splash, a wild “Hurrah!” and five minutes later they were once more on their way to the Pole.

But, during this time, Dave’s active mind had been working on another problem, which might appear to have been settled, but had not been:  the drift of the floe.  If the ice did not pile when the floes came together, why was it?  It seemed to him there could be but one answer; other water-channels beyond the drift, under which they now traveled, were being closed by counter-currents.  And if they closed, one after the other, more rapidly than the advance of the submarine, what was finally to become of the submarine crew?  Would they not perish for lack of air?  Dave did not share the cheerful mood of the Doctor and the crew; it was his turn to look worried.

Many hours later, his worst fears having been realized, he found himself again in the little room of many wheels and dials.  Hour after hour they had shot beneath the varying surface of the floe, but not for one hopeful second had they caught the dark shadow of open water.  As near as he could reckon, allowing for the ever-present currents, Dave believed they were nearing the Pole.  But his brain was now throbbing as if a hundred trip-hammers were pounding upon it.  Moments alone would tell the tale, for the oxygen in the air was exhausted.  Already half the crew were unconscious; others were reeling like drunken men.  The Doctor had been the first to succumb to the poison of polluted air.

In this crisis Dave was not alone at the wheel.  The Eskimo boy, Azazruk, was by his side.  It was for just such a time as this that he had taught the bright young native something of the control of the mechanism.

Each wheel of the operating devices was numbered.  He had taught the Eskimo a formula by pains-taking repetition.

“If ever the time comes when all are sick, no one can move but you,” he had said many times, “and if at that time you see black waters above, act quickly.  One—­seven—­ten—­three—­five, remember that.  One wheel at a time, quickly but surely; one—­seven—­ten—­three—­five.”

“One—­seven—­ten—­three—­five,” the Eskimo boy had faithfully repeated after him, and rolled his eyes half in amusement and half in terror.

“Wheel one is for rise, seven for fans, ten to stop, three to lift the outer-hatch, five the inner-hatch,” Dave had explained.  “But you only need to remember one—­seven—­ten—­three—­five.”

Somehow, Dave had come to believe that this hardy young Alaskan, reared as he had been, under perfect conditions of food, air, light and exercise, could, if the test ever came, survive his civilized companions.

Now, as he reeled and a great wave of dizzy sickness came over him, while he sank to the floor, Dave was glad he had taught Azazruk; for the boy, with a strange, strained look of terror in his eye, stood still at the wheel.