The line between the battery and the observation post is the most important of the whole system, for, without it, properly directed fire is impossible. It is also, from the fact that the observation post is usually close to the front line, the most exposed, and therefore most liable to accident. To lay a wire between two given points may seem to be the simplest thing in the world, as indeed it is, but so to lay that wire that it will not constantly be cut is a fine art. There are two ways of laying it, overhead amongst trees and other supports, or underground, digging a narrow trench in which to bury it. The first method is the quickest, and if a line is required for use immediately, the best plan is to lay it overhead, and bury it subsequently if required. But many perils lie in wait for an overhead line. Lay it by any route you will, some wandering shrapnel will burst near by, and one of the bullets, singling out the wire as though it were its especial target, will cut it neatly through, for preference at its most inaccessible point. But the enemy is by no means its greatest danger. There are roads to cross, along which come heavy lorries laden high with stores of all kinds. Put the line up as high as you think absolutely safe, and sooner or later an extra tall load brings it down. Or natural support, such as trees or houses, fails, and at considerable pains you plant a row of light posts. The next party of wire layers that comes along, finding these convenient to their purpose, lay their own line on them in addition. So the process continues, until the light posts, that you designed to carry one wire only, collapse under the strain, and down comes the whole tangle. Worst of all are the unpardonable crimes of some miscreants, who, running short of wire, cut off as much from your line as they require, leaving the cable with a yawning gulf in the middle, or, as a variation, tap their own instruments on to the wire, when the unfortunate observation officer is left to play a maddening game of cross questions and crooked answers with some strange unknown battery. If, on the other hand, the wire is laid underground, a high-explosive shell is sure to find it and make a neat crater in the middle of it, or else the infantry dig a communication trench across it, or its insulation breaks down late one evening and the ensuing night is spent digging it up and looking for the fault.