A few days after this incident the polar night began to shut down in grim earnest. Sometimes for days the boys and the other adventurers would be confined to the huts. Entertainments were organized and phonograph concerts given, and, when it was possible to venture out, hunting trips in a neighboring seal-ground were attempted. All these things helped to while away the monotony of the long darkness. In the meantime the commanders of the expedition laid their plans for the spring campaign, when the boys' aerial dash was to be made.
On one of the milder nights, when Frank and Rastus were on watch, their first intimation that a strange and mysterious presence shared their lonely vigil was made manifest. It was Rastus who called Frank's attention to what was eventually to prove a perplexing puzzle to the pole hunters.
As the colored man and Frank were pacing outside the huts, keeping their watch, the negro suddenly gripped the boy's arm.
"Fo' de lub ob goodness, man, wha's dat?" he exclaimed, getting as pale as it is possible for a negro to become.
"What?" demanded the boy. "I can't see anything."
He stared about him in the gloom.
"Ain't nuffin ter SEE," rejoined Rastus, in a low, awed tone. "But, hark!"
The negro's ears, sharper than those of the white boy, had caught a sound that later became audible to Frank.
It was a most peculiar sound.
Coming from no one direction that one could indicate with certainty, it seemed to fill the whole air with a buzzing noise that beat almost painfully on the eardrums.