“I’ve heard ’em.  They use ’em in the hills back of us at home.  The sound will carry a tremendous distance on a still night like this.  Do you think it was intended as a signal?”

“It’s impossible to say, but I think so.  I think, too, that the bands—­ there were two of them, one replying to the other—­belong to the Slade and Skelly outfit.  Skelly has lived all his life in the mountains and Slade is learning ’em fast.”

“Then it behooves us to be watchful, and yet more watchful.”

“It does.  Maybe they’re attempting an ambush, with which they might succeed against an ordinary troop, but not against such a troop as this, led by such a man as Colonel Winchester.  Hark, did you hear that noise?”

All of them listened.  It sounded at first like the cow’s horn, but they concluded that it was the rumble, made by sliding snow, which would be sending avalanches down the slopes all through the night.

“Are you going out again, Mr. Shepard?” Dick asked.

“I think not, sir.  Colonel Winchester wants me to stay here, and, even if the enemy should come, we’ll be ready for him.”

They did not speak again for a while and they heard several times the noise of the sliding snow.  Then they heard a note, low and deep, which they were sure was that of the cow’s horn, or its echo.  It was multiplied and repeated, however, so much by the gorges that it was impossible to tell from what point of the compass it came.

But it struck upon Dick’s ears like a signal of alarm, and he and all the others of the picket stiffened to attention.

CHAPTER XIII

DICK’S GREAT EXPLOIT

It was a singular and weird sound, the blowing of the great cow’s horn on the mountain, and then the distant reply from another horn as great.  It was both significant and sinister, such an extraordinary note that, despite Dick’s experience and courage, his hair lifted a little.  He was compelled to look back at the camp and the coals of the fire yet glowing to reassure himself that everything was normal and real.

“I wish there wasn’t so much snow,” said Shepard, “then the sergeant, Mr. Reed and myself could scout all over the country around here, mountains or no mountains.”

They were joined at that moment by Reed, the long mountaineer, who had also been listening to the big horns.

“That means them gorillers, shore,” he said.  “We’ve got some p’ison people uv our own, an’ when the gorillers come in here they j’ined ’em, and knowin’ ev’ry inch uv the country, they kin guide the gorillers wharever they please.”

“You agree then with Mr. Shepard that these signals are made by Slade and Skelly’s men?” asked Dick.

“Shorely,” replied the mountaineer, “an’ I think they’re up to some sort uv trick.  It pesters me too, ’cause I can’t guess it nohow.  I done told the colonel that we’d better look out.”