a fifteen hours before. We had crossed the
pole in safety. It looked as if we might succeed in this attempt to
penetrate the last white spot on the map. Then it Happened.

A sudden crack of snapping metal rang out sharp as a pistol report. A
bright blade of metal flashed past the wing-struts, to fall in a
flashing arc. The motor broke abruptly into a mad, deep-voiced roar.
Terrific vibration shook the ship, until I feared that it would go to
pieces.

Ray Summers, with his usual quick efficiency, cut the throttle.
Quickly the motor slowed to idling speed; the vibration stopped. A
last cough of the engine, and there was no sound save the shrill
screaming of the wind in the gloomy twilight of this unknown land
beyond the pole.

"What in the devil!" I exclaimed.

"The prop! See!" Ray pointed ahead.

I looked, and the dreadful truth flashed upon me. The steel propeller
was gone, or half of it at least. One blade was broken off at a jagged
line just above the hub.

* * * * *

"The propeller! What made it break? I've never heard--"

"Search me!" Ray grinned. "The important thing is that it did. It was
all-metal, of course, tested and guaranteed. The guarantee isn't worth
much here. A flaw in the forging, perhaps, that escaped detection.
And this low temperature. Makes metal as brittle as glass. And the
thing may have been crystallized by the vibration."

The plane was coming down in a shallow glide. I looked out at the grim
expanse of black ice-crags and glistening snow below us, and it was
far from a comforting prospect. But I had a huge amount of confidence
in Ray Summers. I have known him since the day he appeared, from his
father's great Arizona ranch, to be a freshman in the School of Mines
at El Paso, where I was then an instructor in geology. We have knocked
about queer corners of the world together for a good many years. But
he is still but a great boy, with the bluff, simple manners of the
West.

"Do you think we can land?" I asked.

"Looks like we've got to," he said, grimly.

"And what after that?"

"How should I know? We have the sledge, tent, furs. Food, and fuel for
the primus to last a week. There's the rifle, but it must be a
thousand miles to anything to shoot. We can do our best."

"We should have had an extra prop."

"Of course. But it was so many pounds, when every pound counted. And
who knew the thing would break?"

"We'll never get out on a week's provi