"There it is to starboard!" exclaimed the Doctor. Careful backing and
steering to starboard brought merely the disclosure that the Doctor's
eye-strain had developed to the point where it produced optical
illusions.

The oxygen was all this time dwindling. To avoid further waste of time,
Dave told his first mate to close his eyes for three minutes while he
kept watch, then to open them and "spell" him at the watch.

"Straight ahead! Quick!" muttered the mate, as the dial hung
fluttering at zero.

Seizing a lever here and there, watching this gauge, then that one, Dave
sent the craft slanting upward. Like some dark sea monster seeking air,
the "sub" shot toward the opening.

And now--now the prow tilted through space. Another lever and another,
and she balanced for a second on the surface. For a second only, then
came a crash. Too much eagerness, too great haste, had sent the
conning-tower against the solid six-foot floe.

With lips straight and white Dave grasped two levers at once. The craft
shot backward. There followed a sickening grind which could only tell of
interference with the propeller. Too quick a reverse had sent it against
the ice astern. Shutting off all power, Dave allowed her to rise
silently to the surface. Then, as silently, one member of the crew
opened the hatch and they all filed out.

"Propeller's still there," breathed one of the gobs in relief.