y yes!" agreed Joe. "But look, here comes Drew on the run. I
wonder what's happened."

They saw their friend the private rushing toward them, and waving his
hands. He was shouting, but what he said they could not hear.

And then, so suddenly that it was like a burst of fire, Blake, Joe and
Charles experienced a strange feeling! Some powerful odor overpowered
them! Gasping and choking, they fell to the ground, dimly hearing Drew
shouting:

"Gassed! Gassed! Put on your masks!"

CHAPTER XX

"GONE!"

Rolling down upon the American and French battlelines, coming out of the
German trenches, where it had been generated as soon as it was noted
that the wind was right, drifted a cloud of greenish yellow, choking
chlorine gas.

Chlorine gas is made by the action of sulphuric acid and manganese
dioxide on common salt. It has a peculiar corrosive effect on the nose,
throat and lungs, and is most deadly in its effect. It is a heavy gas,
and instead of rising, as does hydrogen, one of the lightest of gases,
it falls to the ground, thus making it dangerously effective for the
Huns. They can depend on the wind to blow it to the enemy's trenches and
fill them as would a stream of water.

Knowing as he did the deadly nature of the gas from his own experience
and that of his comrades, some of whom had been killed by it, Private
Drew lost no time in sounding his warning to the moving picture boys.
He had taken part in the raid on the Germans, had seen and engaged in
some hard fighting, and had been sent to the rear with an order from his
officer. And it was as he started that he saw, from one section of the
Hun lines, the deadly gas rolling out.

He knew from the direction and strength of the wind just where it would
reach to, and, seeing the moving picture boys in its path, he called to
them.

"Put on your masks! Put on your masks!" cried the soldier. At the same
time, as he ran, he loosed his from where it hung at his belt and began
to don it.

The gas masks used in the trenches are simple affairs. They consist of a
cloth helmet which is saturated with a chemical that neutralizes the
action of the chlorine. There are two celluloid eye holes and a rubber
tube, which is taken into the mouth and through which the air breathed
is expelled. All air breathed, mixed as it is with the deadly chlorine,
passes through the chemical-saturated cloth of the helmet and is thus
rendered harmless. But it is a great strain on those