he 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."

Colonel Winchester joined them as he was speaking, and listened to the
double signal which was repeated later. But it did not come again,
although they waited some time. Instead they heard, as they had heard
all through the night, the occasional swish of the soft snow sliding
down the slopes. But Dick saw that the colonel was uneasy, and that his
apprehensions were shared both by Shepard and the mountaineer.

"Do you know how many men these