With the quick atmospheric change of the arctic—­a phenomenon common to zones of extreme temperature—­the wind steadily increased in velocity and warmth.  The shallow moon-shot clouds on the ice thickened and swept softly under the two travellers’ feet.  Above their waists the air was clear—­they saw each other distinctly in the moonlight.  Yet their dogs, hidden in the low-lying vapor, were invisible.  Great masses of clouds slowly piled along the horizon and the moon was often obscured.  Then the two walked in a darkness so thick it seemed palpable.

“Hark!” Ootah called, during one of these spells.  “What is that?” A shuddering sound split the air; the ice field on which they travelled vibrated with an ominous jar.  The echoes of splitting ice came like distant explosions.

“Have we disturbed the spirits of the hills?” asked Koolotah, in a whisper.

“No, no,” answered Ootah, anxiously. “Huk! Huk!” He snapped his whip and urged the dogs.  They had not gone twenty paces when from the interior heights of Greenland came a series of muffled explosions.  Undoubtedly the hill spirits had wakened, and, angry, were hurling their terrible weapons.

They reached, in due course, the top of a mountain ridge down part of the glassy slopes of which they had to make their way to the entrance of the cleft in which the trail they had so laboriously hewn lay.  The gorge yawned blackly some five hundred feet below.  In anticipation of their return with loaded sledges, Ootah, on the last reach of their upland climb, had chopped on the smooth snows of the mountainside a narrow path that ran backward and forward in the fashion of a gently inclining elongated spiral.  The mountain sloped at an angle of eighty degrees, but by descending cautiously along this circuitous trail a safe descent was possible.

While Ootah and his companion stood on the peak, the moon passed behind a veil of clouds and Ootah felt two soft wraith-like hands pass over his face—­cloud-hands which his simple mind believed were sentient things.  His heart for the moment seemed to stop.  Thus the kind spirits warn men of danger.

At that instant a stinging sound smote the air.  The glacial side of the mountain trembled, and as the moon reappeared, on the icy slopes Ootah saw narrow black cracks zigzagging in various directions.  A cataclysmic rumbling sounded deep in the earth.

When the echoes died away he turned to Koolotah.

“Be brave of heart.  Let us go—­there is no time to lose.”

“Huk! Huk! Huk!” They urged the dogs gently.  Arranging themselves instinctively in single file, the traces slackening, the wonderful dogs, with feline caution, crept ahead.  Lowering their bodies, each behind his sledge, Ootah and Koolotah began moving stealthily downward.  With one hand each clung to the rough icy projections of the slope; with the other they held the rear upstander of their sleds to prevent them from sliding, with their precious loads of meat, down the mountainside.