But now there came to their ears a sound like the distant rush of many
waters. This grew rapidly louder, and finally divided itself into
rattling and snapping sounds.

Presently the Major let out a roar of laughter.

"Caribou!" he exploded. "They pass south from the barren lands in herds
of hundreds of thousands, so thick they look like land! Tip her nose up
for another circle. See! There is the end of the herd away there in the
distance. We'll be able to land where they have passed in fifteen
minutes, an ideal landing-place--tramped hard."

With a grin Barney obeyed orders, and, as his engines began to revolve,
felt himself shooting skyward.

"Now it's clear," roared the Major.

Barney did not respond on the instant. He was thinking of something he
had read about the "camp-followers of the barren-ground caribou." A chill
not of the wind and cold crept into his heart. But what was to be done?
He felt that another hour aloft would so benumb his senses that a crash
would be inevitable. To land at a point other than that trampled by the
caribou involved great risk, for there was undoubtedly a thick coating of
drifted snow on the lake's surface. So he stopped the engines and they
spiraled once more toward the earth.

Now they were nearing the surface of the lake. The distance was a
thousand feet; now eight hundred. Did he see shadows flitting across the
ice? At five hundred feet he was sure that he did. He said nothing. So
intent on landing was he that no risk seemed too great. At three hundred