"Besides that, a thin wavy line is much more difficult to see from an aëroplane than a straight line, because there are no straight lines in nature. That's why we've had to stop putting straw in the trenches, the line of yellow was too easy to see from overhead." "Is that why trenches are made so narrow?" the boy asked. "I've often thought it silly to make them so that two people can hardly squeeze past each other. The stretcher-bearers growl about it all the time." "The ideal fire-trench," the veteran answered, "should be only about eighteen inches wide and not quite four feet deep, the upthrown earth forming a parapet. It should be recessed here and there, and traversed. To pass a man, you have to slide sideways. The communicating trench should be about fifteen yards to the rear. It should be seven feet deep and about three feet wide. "Twenty-five yards in the rear is the cover trench, sixteen feet deep, and wide enough to allow troops to march in single file. The communication trenches from one line to another are always best as tunnels, though sometimes they are open. Our trenches here are open, but," the veteran nodded sagely, "I don't think they ought to be. This is a chalk soil, and the whitish soil underneath shows too clearly when you throw it up." "The trenches wouldn't be so bad," said the lad, "if they weren't always wet." "You can't change that," the veteran responded grimly, "unless you can find some way to make water run up-hill. It stands to reason that if you dig holes in the ground and it rains--as it does nearly all the time in this wretched northern country--the water is going to run into those holes. If you bale it out by day, the Boches see you, and if you pump at night, they hear you. If it rains, the trenches are going to be knee-deep in water and you can't help it." "But how can you find your way, when one trench looks exactly like another and they're all twisting and turning like so many snakes trying to get warm?" "You can't, unless you know the plans," the sergeant-major answered. "You've no idea of the amount of work that our draughtsmen have to do, in mapping out these underground cities and thousands of miles of ditch-streets. I know my little section, of course, and each officer has learned the tangle of trenches in which his command is likely to operate. But the officers have to know the tangle of the enemy's trenches, too, and, what's more, when we attack, they have to be in the front and guide us. An assault isn't just a blind drive over the top, it must have a definite goal and has to be reached a certain way. The officers have got to know the Boche roads as well as our own." "But how can they find that out?" "Aeroplanes with photographers and draughtsmen," came the reply. "You've heard the story of the tattooed draughtsman?" "No," answered Horace, "I haven't."