2. How may the range of a projectile be extended? Either by raising the piece to a higher level, or by giving its axis greater elevation within certain limits. 3. Define _point-blank range_. The distance from the muzzle of the piece to that point in a shot’s trajectory where it cuts the prolongation of the natural line of sight, a second time. 4. In what does the French definition for point-blank range differ from ours? It requires that the natural line of sight should be horizontal. 5. What is the British definition for point-blank range? The distance from the muzzle to the first graze when the axis of the piece is parallel to the plane upon which the carriage stands. 6. Explain by a figure, the position of, and relations existing between the line of sight, the line of fire or axis of the piece, and the trajectory, and also what the point-blank range is. [Sidenote: 64]] [Illustration: _Fig. 1_] _ABcF_, the line passing through the highest points of the base ring and swell of the muzzle, or the muzzle-band, is called, _the natural line of sight_. _EPcG_, is the _axis of the piece_ or _line of fire_; the curved line, _PgD_, described by the projectile, is called the _trajectory_, and is entirely below the line of fire, in consequence of the action of the force of gravity giving the projectile a downward tendency. The point D is called the _point-blank_, and its distance from the mouth of the piece, the _point-blank range_. 7. Mention some of the causes which vary the point-blank range. The form of the cannon; the weight or force of the charge; the diameter and weight of the projectile; and the inclination of the line of sight to the horizon. 8. Why has the form of the cannon an influence on the point-blank range? Because as the difference between the diameter of the breech and muzzle become greater, the angle of sight, _BcP_ = _GcF_ (see fig.) increases, and the point-blank D is removed farther off; on the contrary, as the diameters approach to an equality, the point-blank approaches the piece. Within a certain angle, or when there is no angle of sight, as is the case with some old howitzers in which the line of sight is parallel to the axis of the bore, there will be no point-blank, as the trajectory will be constantly below the line of sight. [Sidenote: 65]] 9. What influence has the charge on the point-blank range? An increase of the charge determines a more distant point-blank; its diminution produces a contrary effect: but beyond a charge equal to one-third the weight of the ball, the increase of range is inconsiderable, and the force of the recoil becomes very great. 10. How do the diameter and weight of the projectile affect the range? As the ball increases in size and density, it will overcome with more ease the resistance of the air. 11. Does the inclination of the line of sight to the horizon have much effect on the point-blank range?