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 who wear the masks, for nothing like the right kind of breathing can be done. In fact, a diver at the bottom of the sea has better and more pure air to breathe than a soldier in the open wearing a gas mask.
It was the first experience of Blake and his chums with the German gas, though they had heard much about it, and it needed but the first whiff to make them realize their danger.
Even as Private Drew called to them, and as they saw him running toward them and trying to adjust his own mask, they were overcome. As though shot, they fell to the ground, their eyes smarting and burning, their throats and nostrils seeming to be pinched in giant fingers, and their hearts laboring.