From a distance of two miles the ambulance men had been watching the engagement, waiting for the signal to come forward to transport the wounded men. The field glasses betrayed every movement on the battle line. Suddenly, and without any apparent cause, the Allied lines seemed to break, and the fields were alive with running figures. Astonishment took hold of the spectators. The impossible had happened, and the French Army was in wild retreat. Figures were seen tottering and stumbling across the meadow, soldiers were reeling to and fro, staggering like drunken men. Falling down upon the ground, waving their arms frantically, they kicked their legs in the air, agonized and groaning. Some of them came into the Red Cross dressing station, coughing, choking, and strangling. Their faces were green and their chests were heaving. Between gasps, they related an incredible tale. The Germans had opened up a bombardment of our trenches with some new, but hellish, weapon. A greenish, gray gas had appeared above them, and hung low, instead of rising. It seemed to be heavier than air, and soon it made its way down into the trenches, choking our men and throwing them into a state of terror. They tried to fan it away with their blankets. But no use, it only spread the gas, which got into their throats and lungs and tortured them beyond all description. "God knows we will fight like men," they said, "but to be smothered like rats is different. No human being could endure such suffocation. God never meant a man to breathe that stuff and we'll make those hell-hounds pay for it." But hundreds of poor poilus had already "gone West," and those who escaped were in such a condition of permanent disability and weakness that there was no danger of their making the Germans pay. Many Canadians, too, brave fellows, died that day, but on that day also they became immortal. The stretcher bearers had seen it all, and now upon the signal, plunged into the work of lifting the sufferers into the ambulances and carrying them back to be treated and cared for. For days this thing endured, until at last the Allies devised a gas mask or respirator which completely nullified the effects of the deadly chlorine, but they paid an awful price before they got it. It is a very simple device, consisting of a long cap of light canvas or similar material, soaked in a chemical solution which absorbs or neutralizes the poison of the gases. The cap has large eye holes with glass windows. The air from the lungs is expelled through a tube which has an outward opening valve, so that you must breathe in through the treated gauze. One's coat is buttoned tightly around the lower end of this cap or "smoke helmet," so that no gas can enter from below. It is put on in twenty seconds and can withstand five hours of the poison gas.