We had taken over a bank and some shallow, aged dug-outs, occupied the night before by our C Battery; and as there was a chill in the air that foretold rain, and banks of sombre clouds were lining up in the western sky, we unloaded our carts and set to work getting our belongings under cover while it was still light. "There's no pit for you to dig in," the colonel told me quizzingly, "but you can occupy yourself filling these ammunition boxes with earth; they'll make walls for the mess." Hubbard had been looking for something heavy to carry; he brought an enormous beam from the broad-gauge railway that lay a hundred yards west of us. The colonel immediately claimed it for the mess roof. "We'll fix it centre-wise on the ammunition boxes to support the tarpaulin," he decided. "Old Fritz has done his dirtiest along the railway," said Hubbard cheerfully. "He's taken a bit out of every rail; and he's blown a mine a quarter of a mile down there that's giving the sappers something to think about. They told me they want to have trains running in two days." Meanwhile the signallers had been cleaning out the deep shaft they were to work in; the cooks and the clerks had selected their own rabbit-hutches; and I had picked a semi-detached dug-out in which were wire beds for the colonel, Hubbard, and myself. True, a shell had made a hole in one corner of the iron roof, and the place was of such antiquity that rats could be heard squeaking in the vicinity of my bed-head, but I hoped that a map-board fixed behind my pillow would protect me from unpleasantness. The colonel was suspicious of the S.O.S. line issued to us by Division that night. The ordinary rules of gunnery provide that the angle of sight to be put on the guns can be calculated from the difference between the height of the ground on which the battery stands and the height at the target. More often than not ridges intervene between the gun and the target, and the height and position of these ridges sometimes cause complications in the reckoning of the angle of sight, particularly if a high ridge is situated close to the object to be shot at. Without going into full explanation, I hope I may be understood when I say that the correct angle of sight, calculated from the map difference in height between battery and target, occasionally fails to ensure that the curve described by the shell in its flight will finish sufficiently high in the air for the shell to clear the final crest. When that happens shells fall on the wrong side of the ridge, and our own infantry are endangered. It is a point to which brigade-majors and brigade commanders naturally give close attention.