It was a warm day in early March. Private Ellis was in No. 5 Box, opposite Aeroplane Trench. This post was very cunningly concealed. Our front trench ran along a road, immediately behind which was a steep chalk bank, the road having originally been cut out of a rather steep slope. You will see the lie of the ground clearly enough on Map III. Just about five yards behind this bank was cut a deep narrow trench, and in this trench were built several snipers’ posts, with loopholes looking out of the chalk bank. These loopholes were almost impossible to see, as they were very nearly indistinguishable from the shadows in the bank. Anyone who has hunted for oyster-catchers’ eggs on a pebbly beach knows that black and white is the most protective colour scheme existing. And so these little black loopholes were almost invisible in the black and white of the chalk bank. All the morning Private Ellis had been watching out of the corner of his eye a little bit of glass shining in Aeroplane Trench. Now Aeroplane Trench (as you will also see from the map) was a sap running out from the German front trench into a sunken road. From the centre sap two little branch saps ran up and down the road, and then slightly forward; the whole plan of it rather resembled an aeroplane and gave it its name. In it to-day was a Boche with a periscopic rifle; and it was this little bit of glass at the top of the periscope, and the nose of the rifle-barrel that Private Ellis was watching. Every now and again the glass and nose-cap would give a little jump, and “plop” a bullet would bury itself in our front parapet. One of our sentries had had his periscope smashed during the morning, I was informed by a company commander with rather the air of “What’s the use of you and your snipers, if you can’t stop them sniping us?” I told Ellis about the periscope, to which he replied: “It won’t break us, I guess, sir--twopenn’orth of new glass for a periscope. It’s heads that count.” In which remark was no little wisdom. “Crack--plop,” and after a long interval another “Crack--zin--n--n--g,” as a bullet ricocheted off a stone, and went away over the ridge and fell with a little sigh somewhere in the ground right away beyond Redoubt A. So it went on all the afternoon, while the sun was warming everyone up and one dreamed of the summer, and warm days, dry trenches, and short nights. Ellis had gone off rather reluctantly at midday, and the other relief was there. There was a slumbrous sensation about that brought on the feeling that there was no one really in the enemy trenches at all. Yet there was the little glass eye looking at us: it reminded one of a snake in the grass. It glittered, unblinking. At about six o’clock I again visited the post. Ellis was back there, and watching as keenly as ever. “No luck?” I remarked. “I’m afraid your friend is too wily for you; he’s not going to put his head over, when he can see through a periscope as well.”