=Slow Fire= is used at long ranges and for obtaining the range, and generally in the commencement of the action and during the artillery duel; it is also used in prolonged actions, and when the ammunition is running short. The interval between successive shots should not be less than 30 seconds, and may be slower. =Ordinary Fire= is used when the fire is effective, but when the circumstances of the action do not demand a rapid fire. It is at the rate of 1 shot every 20 seconds, or, in a six-gun battery, 6 rounds in 2 minutes. =Rapid Fire.=--The rate is about one round in 7 seconds; it should be sufficient to enable the effect of a shot to be observed before firing the next one. _The range being accurately known_, it is used: when the enemy's batteries are coming into action; when there is a very favorable target; when a rush is made to pass a defile; when covering the advance of one's own artillery; when the decisive infantry attack is about to take place; when the advance is checked during a critical situation; when the opportunity to fire is very fleeting; at short ranges. The instant the necessity for rapid fire ceases to exist the fire should revert to the ordinary rate. TARGETS MOVING TOWARDS THE BATTERY. The range is found by trial shots, the elevation being increased or reduced by stages of 100 or 200 yards, depending on circumstances. As soon as a shell is observed to fall not too short (within 100 yards of the advancing target) all the guns fire a round rapidly. If infantry is being fired at, each subsequent round should have its range diminished by 100 yards; if cavalry or artillery, at a trot or gallop, it should be diminished 200 and 300 yards respectively. TARGETS MOVING FROM THE BATTERY. Two elevations differing by 100 yards are obtained as before; with the lower of the two a salvo of shrapnel is fired from all the guns in the battery, the proceeding is then repeated, and so on. TARGETS MOVING OBLIQUELY AND ACROSS THE FRONT OF THE BATTERY. If the target is of great length, aim at the head of it; if not of great length or moving rapidly, aim in front of it. Under certain circumstances it is advisable to ascertain the range of points in the line of march of the target. When the moving target reaches one of these points, fire rapidly. Infantry cover 1½ yards a second at a quick walk, and artillery and cavalry 2 yards a second at a quick walk, 4 yards at a trot, and 6 yards at a gallop. By multiplying the rate per second of the target by the time of flight of a shell, we obtain the distance the target has moved over during the flight of the shell. INDIRECT FIRING. In firing at an object which cannot be seen from the gun several methods are employed, depending on the circumstances of the case.