rly he and his comrades
sprang forward. They passed a little trench near the mouth of the
cave. In this shallow ditch were several iron cylinders from holes of
which was pouring a white vapor. This was the gas, how deadly could
only be surmised for the masks kept all fumes and effects of it from
the attackers.

There was a current of air from the cave blowing down the defile and
this carried the fumes away from the hidden men and into the ranks of
the attackers. This direction of the wind explained why no gas masks
were needed by the foe. The wind was their protection. And the fact
that they wore no masks was soon demonstrated.

For as the attackers swept on and up to the cave they dislodged several
of the first line fighters of their foes--rough, ugly-looking men who
sprang up from amid the rocks and, after firing their last shots,
turned and ran into the cavern. Not one wore a mask.

In a few minutes the attackers were safely back of the gas-emitting
cylinders and could take off their masks for the wind carried the fumes
away from them. Yanking his protector off, Bud shouted:

"Into the cave after them!"

The rush was made. A sight was had of a crowd of men retreating into
the black depths of the cavern. The cowboys fired at them and were
shot at in turn, Nort receiving a nasty scratch from a bullet along his
shoulder, and his brother stopping a lead slug in the fleshy part of
his thigh. Bud was nipped on the hand and several of the other cowboys
were more or less painfully injured.

Some damage was inflicted on the foe, for there were yells of pain from
several and one man was seen to fall. He was quickly picked up by his
pals, however, and carried into the far end of the cave.

Then, when it grew dark as the daylight faded, a short distance beyond
the entrance, Bud called a halt on further pursuit.

"No use going back there when we don't know what's beyond," he said.
"We've driven 'em out, and we can have a look, now, and see what secret
they have been guarding."

When Snake and Kid, again donning their masks, had shut off the flow of
gas from the cylinders, a precaution taken against a possible change of
wind, flashlights were produced and a close inspection of the cave was
begun. It was evident that the men who had been in it, and who had
relied on gas to keep intruders out, had made their escape through some
rear exit, or they might still be hiding in the depths of the cavern.

Extra powe