"They probably are," Joe reassured her. "Probably picked up by another wagon."
They drove on, sobered by this evidence of certain accident, and possible tragedy, along the Oregon Trail. The hard trail continued; rain country was definitely behind. But a cold north wind still blew and Joe urged on the mules. There was no summer weather behind that wind and he had no desire to be caught out here when snow fell. For a moment they rode in silence, and it seemed that there was something alien among them. Even the children were still, and Emma turned to Joe, vaguely puzzled.
"Do you hear anything?"
"By gosh, I thought I did."
"I too."
There was a distant, muted throbbing that came to them in discordant tempo, like a wind that blows in blasts instead of with steady force. But the wind around the wagon was still steady and still from the north. Joe twisted uneasily on the wagon seat, for it seemed to him that there was much he should know about this that he did not know. He had a sense of danger, which was silly, for no danger threatened. The mules bobbed uneasy heads.
"Hey, Pa!"
Tad's voice was desperate and wild. Running hard, the youngster appeared on a near-by knoll. Joe stopped the team and waited, while fear's cold fingers caressed his spine. Tad's jacket was open, his face sweat-streaked, and he had run so far and so fast that he gasped for breath.
"My gosh!" he yelled. "Must be a million of 'em!"
"A million what?"