At night, when he mounts his gun over the top of his trench and wants to get the range of Fritz's trench he adopts the method of what he terms "getting the sparks." This consists of firing bursts from his gun until the bullets hit the German barbed wire. He can tell when they are cutting the wire, because a bullet when it hits a wire throws out a blue electric spark. Machine-gun fire is very damaging to wire and causes many a wiring party to go out at night when it is quiet to repair the damage. To disguise the flare of his gun at night when firing. Tommy uses what is called a flare protector. This is a stove-pipe arrangement which fits over the barrel casing of the gun and screens the sparks from the right and left, but not from the front. So Tommy, always resourceful, adopts this scheme. About three feet or less in front of the gun he drives two stakes into the ground, about five feet apart. Across these stakes he stretches a curtain made out of empty sandbags ripped open. He soaks this curtain in water and fires through it. The water prevents it catching fire and effectively screens the flare of the firing gun from the enemy. Sound is a valuable asset in locating a machine gun, but Tommy surmounts this obstacle by placing two machine guns about one hundred to one hundred fifty yards apart. The gun on the right to cover with its fire the sector of the left gun and the gun on the left to cover that of the right gun. This makes their fire cross; they are fired simultaneously. {Illustration: Diagram} By this method it sounds like one gun firing and gives the Germans the impression that the gun is firing from a point midway between the guns which are actually firing, and they accordingly shell that particular spot. The machine gunners chuckle and say, "Fritz is a brainy boy, not 'alf he ain't." But the men in our lines at the spot being shelled curse Fritz for his ignorance and pass a few pert remarks down the line in reference to the machine gunners being "windy" and afraid to take their medicine. CHAPTER XXIII GAS ATTACKS AND SPIES Three days after we had silenced Fritz, the Germans sent over gas. It did not catch us unawares, because the wind had been made to order, that is, it was blowing from the German trenches towards ours at the rate of about five miles per hour. Warnings had been passed down the trench to keep a sharp lookout for gas. We had a new man at the periscope, on this afternoon in question; I was sitting on the fire step, cleaning my rifle, when he called out to me: "There's a sort of greenish, yellow cloud rolling along the ground out in front, it's coming--" But I waited for no more, grabbing my bayonet, which was detached from the rifle, I gave the alarm by banging an empty shell case, which was hanging near the periscope. At the same instant, gongs started ringing down the trench, the signal for Tommy to don his respirator, or smoke helmet, as we call it.