=7. Method of Explaining Trajectory.=[6]--(i) In explaining the trajectory to recruits it is not sufficient merely to show or draw a diagram representing a trajectory distorted in respect of height and range. When possible the actual path of the bullet through the air at various short ranges--say 400 and 800 yards--should be shown by means of discs raised on poles at every 100 yards, or some similar device. (ii) It must be explained to the soldier that the further an object has to travel and the longer it is suspended in the air, the higher it must be thrown to counteract the force of gravity, because the greater the distance it travels and the longer it remains in the air the longer will the object be affected by the force of gravity. Consequently the longer the range the higher will the curve of the trajectory take the bullet in its flight, and the steeper will be the angle at which it will fall to the earth. (iii) On the other hand, the shorter the distance an object is thrown, and the swifter its flight through the air, the less will it be influenced by the force of gravity during its flight, and the lower or flatter will its trajectory be in consequence. Thus, with the backsight adjusted for the distances in question, a Mark VI bullet does not rise above the height of a man on foot at 500 yards range, or above the height of a mounted man at 600 yards range. With Mark VII ammunition, the bullet does not rise above these heights at 600 and 700 yards range respectively. =8. Firing at Close Range without Altering Sights.=--_It is therefore evident that effective fire can be maintained within close range without alteration of the backsight._ Apart from the flatness of the trajectory at close range, and the consequent inclusion of distances within close range in dangerous space (Sec. 9), there will seldom be opportunities for altering sights at close range on service, and necessary allowances for elevation must be made by aiming up and down (Sec. 21). =9. Elevation.=--In order to allow for the fall of the bullet, owing to the force of gravity, it is necessary to direct,the line of departure as much above the object to be hit, as the bullet will fall below it at any given distance if the axis of the barrel of the rifle is pointed at the mark. This raising of the barrel to allow for the curve of the trajectory is termed _giving elevation_. The target must of necessity be kept in view. The rifle is therefore provided with sights, which permit the firer to give the elevation required whilst keeping his eye fixed on the mark.