They were now approaching the cave.

"Steady, boys!" called Billee as they rounded a turn and came within
view of the dark entrance to the cavern.

It was a tense moment. Some of the men carried a gun in either hand.
Nort and Dick had one each, and Billee was armed likewise. A little
wind began blowing down the gulch in the faces of the attackers. It
seemed to bring with it a slight mist.

"Gettin' foggy," commented Snake. "I wonder----"

Then he began to cough and choke. So did Nort, Dick and Old Billee.
The white mist came floating nearer.

"Look out, boys!" suddenly shouted Yellin' Kid. "It's a gas attack,
same as in the war. Look out!"

A moment later the party was sneezing, coughing and gasping for breath
as the faint white mist, blown by the wind, enveloped them. It caused
a terrible, gripping sensation, a constriction of the throat muscles so
that breathing was difficult.

"They've got us!" yelled Billee. "We can't fight poison gas! Back up,
boys! We've got to run!"

It was impossible to advance in the face of this mysterious surprise
attack and the avengers were driven back. Gasping, and trying to keep
from collapsing under the afflicting sensation, the Dot and Dash men
were forced to retreat from their unseen foes.

CHAPTER XIX

GAS MASKS

"Hold on!" yelled Snake Purdee as he swung around a ledge at the edge
of the narrow entrance to Smugglers' Glen and made a grab at Nort who
was running as fast as he could under the weakening influence of the
gas. "It's all right here--the wind will blow the stuff to the east.
Swing around here, everybody!" and he indicated a niche to the west of
the entrance.

Nort stopped, his brain dully comprehending what Snake meant. Then the
others in the wild, frightened retreat sensed what the words were
intended to convey and, one after another, they gathered there in
comparative safety with Snake, Nort and Dick.

"Whew!" gasped Billee Dobb whose age was telling on him, not only in
the rapid, forced retreat, but in the effect of the gas. "That was
tough! But what makes you think we'll be safe here, Snake?"

"On account of the wind blowing the gas away from us. Look, there it
floats to the east. We're safe here. I didn't get nearly gassed in
the war for nothing. We're safe here till the wind shifts and it won't
do that right away."

"What about the horses?" gasped Dick, taking deep breaths to rid
himself of the gas already breathed.

"T