The instructor explains that if they take four deep breaths it will prove fatal:  “One breath and you catch the first spasm, two and you are mad, three and you are unconscious, four and you are dead.  If you keep your presence of mind and hold your breath you will have six seconds to get on your gas helmet or respirator.”  The attack, remember, is a surprise in the dark; brain-splitting gas shells are dropping on all sides, and it is hard to keep cool and hold one’s breath in the moment of sudden surprise and panic.  We are told that there are fifteen mistakes which are easily possible in getting on this complicated helmet, or if there is one big blunder in the sudden surprise the man is done for.

Before going through the death chamber, helmets are inspected, to see that they are sound and unpunctured, and the men are drilled in the open to practice putting them on quickly.  Suddenly the warning whistle of an imaginary gas attack sounds.  One backward fling of the head and the steel helmet falls off, for there is no time to lift it off.  A dive into the bag carried on the chest and the respirator is grasped and with one skilful swoop it is drawn over the face.  Your nose is pinched shut by a clamp, your teeth grip the rubber mouthpiece, and, like a diver, you must now get your one safe stream of pure air through the respirator.  You draw in the air from a tube which rises from a tin of chemical on your chest.  Then you can breathe in the dense, deadly, greenish chlorine vapor, for as it passes through the respirator filled with chemicals, it is absorbed, neutralized, oxidized, and purified into a stream of pure air.  All about you may be choking fumes of death which would kill you in four seconds, yet you will be completely immune, breathing a purified atmosphere.

The soldiers are now marched up to this chamber of horrors to walk through the poison gas.  Many have “the wind up” (i. e., they are afraid inside, but are ashamed to show it).  Reliance on the guide, the expert who has been through it all, and the sense of companionship, the stronger ones unconsciously strengthening the weak, have a steadying effect upon all the men.  The soldiers have had four hours’ drill to prepare them, but the “padre” and I, who are now permitted to go through, have had but four minutes.  I am trying to remember a number of things all at once.  Above all I must keep cool and assure myself that there is no danger if only I trust and obey what the expert has said.  I fling on the helmet and we start into the death chamber, but suddenly a string is loose—­will the respirator work?  There seems to be something the matter with my nosepiece which should be clamped shut.  I would like to ask the instructor just one question to make sure, but I can no more talk than a diver beneath the sea.  It is too late, we are moving, I can only hope and trust the helmet will hold.  We have left the sunlight and are in a long dark covered chamber, like a trench, groping