And with this vast increase in material had gone perpetual advance in organisation. Artillery commanders were introduced into all armies and corps, with staffs acting under them. Hence a greater concentration of brain and energy on the special artillery problems--very soon justified by results. Science and experience had full play, and the continuous artillery battle begun on the Somme ended, as it deserved to end, "in the defeat of the enemy's guns." To that defeat new inventions--or the marvellous development of old ones--were perpetually tending. Take sound-ranging for instance, which, with flash-spotting and air photography, has enabled the gunner more and more certainly to locate his enemy's gun while concealing the position of his own. For "the object of a gun or howitzer is to throw a projectile to some spot the position of which is _known_." The older way of knowing was by registration--throwing round after round, and by the help of aeroplane or other observation of the results, getting nearer and nearer to the target till the range was exactly found. By this method, not only is the enemy warned, but your own position is revealed. The newer method aims at _surprise_--the supreme aim of modern war. "The principle of the location of guns by sound," writes an artillery officer, "is simple enough. Suppose there are two observers in the British lines, one at each end of a long line. Bisect this base, and from the middle point draw a line at right angles to the base and towards the German lines. Now, if a hostile gun fires from a position on this line, the sound will reach both observers simultaneously. If the gun fires from a position to the right of the line, the sound will reach the right-hand observer first, and vice versa. Then, by measuring exactly the time-interval between the arrival of the sound at each observation post, the bearing to the gun can be calculated." "Until quite recently the Germans used four human observers, who timed the sound intervals with stop watches. The British used six microphones of a special type, connected electrically with a photographic-recording apparatus. Instead of stop watches, therefore, we used a timing device capable of recording the most minute time-intervals with perfect precision. The whole system was immeasurably superior to the German, and at least twenty times as accurate, for the British system was absolutely automatic. It recorded the arrival of the sound at the various microphones instantaneously on a permanent record; while the German system, apart from its crude method of measuring time, was subject to the combined errors of four human 'microphones.' The British system requires only one forward observer, placed well ahead of the base, and all he has to do is to press a button and start the apparatus before the sound reaches the microphones.