For a long time he had been conscious of the curious, hissing monotone of the Aurora, the "music of the skies," reaching out through the space of the earth with a purring sound that was at times like the purr of a cat and at others like the faint hum of a bee.

Absorbed in his work he did not, for a time, hear the other sound.

Not until he had finished, and was placing the golden snare in his wallet, did the one sound individualize and separate itself from the other.
He straightened himself suddenly, and listened.

Then he jumped to his feet and ran through fifty feet of low scrub to the edge of the white plain.
It was coming from off there, a great distance away.

Perhaps a mile.