Sometimes it is not practical to have an observation post located so as to allow the commander of the battery to see the result and direct the shell fire. In this case he has a balloon which is fastened to the earth by a cable and sent up behind the lines and out of range of the Germans. At best it is an uncomfortable position to be in; hung up in a basket maybe four thousand feet above terra firma, with German fliers hovering about and trying to blow you into eternity. It's not soothing to the nerves to say the least, even though you know that if the balloon takes fire, you have a parachute to drop with. Again the enemy's battery may be situated so that the balloon man cannot find its location. In this case the airplane solves the problem, for it goes to any desired height, then scouts over the enemy's trenches and does the "spotting." Of course, communication with an airplane is not as easy as with a balloon which has wires running to it, but the airplane can send wireless messages down, which are received on the earth, and to make up for the impossibility of the aviator receiving them in return, owing to the noise of his powerful motor, the men on the ground use a system of signals like the wigwag flag method. This is done by large panels which are in distinct contrast to their background, and move according to a certain code. CHAPTER XVIII THE RAGPICKER The salvage from a modern battle is a thing which I suppose few people ever stop to think about. Where hundreds upon hundreds of thousands of men have been engaged in shooting iron and steel as fast as they can fire it, the amount of these metals which lies about is something almost beyond conception. And the amount too, which buries itself beneath the surface of the earth is enormous. The money value and military worth of these vast quantities of metal is also a thing which must be taken into consideration. A battle field today is little less than a great ocean of craters which oftentimes touch one another. Most people, if they thought about it at all, would take it for granted that this debris, this wastage, has gone back to earth from whence it came, there to remain until the elements in the soil and water disintegrate and metamorphose the metals from their present form back to their original state in the bowels of the earth. But this is usually not the case.