Page:The New International Encyclopædia 1st ed. v. 09.djvu/423

* GUNNERY. 373 GUNNERY. then be represented by the line A M G, which is very nuiili nearer the horizontal ])lanc than the curve A E F G. So that if the object fired at be at O instead of at G, as supposed, and if its height is O P, the low-velocity shot will miss it, while the high-velocity one will hit it, notwith- standing Uie error in the assumed range. The diliicully of obtaining the correct range is en- hanced by the movements of the ship firing and the one fired at, the combined movement con- stantly changing the distance, sometimes very rapidly. It is necessary, therefore, to have the range transmitted to the gun as ([uickly as pos- sible after being determined by the range-finder. This renders it desirable to have many range- finders — one for every group of guns, if possible. The reason why so few hits are made in a naval battle in comparison to the shots fired is largely due to the uncertainty of range. At the naval action oft' Santiago the ships were all moving quickly, ami the ranges were changing with great rapidity: Ihe result was. that the United States ships made less than 10>|ier cent, of hits, while the Spaniards probably made not nuich over 1 per cent. In lioth fleets the smoke interfered very much with the shooting: but the greatest source of error was the uncertain range. The personal error of the gun-pointer, which tends to make him habitually shoot high or low, or too soon, or too late, can only be corrected by practice at known ranges. The state of the atmosphere affects the range, but this need not be considered. The horizontal movement of ships has already been referred to. If from a ship W'hicli is not moving, the centre of a vessel 200 feet long moving at the rate of 20 feet per sec- ond ( 12 knots per hour) is fired at, the shot will fall astern of her if she is so far away that it takes more than 5 seconds for the projectile to reach her. If the firing ship is moving in the opposite direction at 12 knots, the shot will miss her if the projectile only takes 2.5 seconds. The allowance is the same sort as that made when shooting at birds on the wing or at moving ani- mals; but it must be very much more carefully estimated. The rolling and pitching of a ship are fruitful sources of error in firing, particularly with poorly trained gun-pointers. Good training and plenty of target practice reduce the errors in a great measure, and nearly eliminate' them when the angle of roll or pitch is small. The greatest effect of rolling through small angles is seen in the decreased speed of fire, for the gun- pointer of a heavy gun must 'wait for the roll' before he can fire, and if the gun is not trained correctly it will not be on the target when the sights roll past it. For this reason, and because the motion is slower then, it is desirable to fire near the end of the roll: this must always be an approximate rule, as one roll may be through an angle of o degrees and the next only through 2 or 3. Guns of 7-inch calibre and less are now fitted with elevating gear which permits them to be kept on the target througliout moderate rolls. The destructive effect of gun-tire depends upon the character of the projectile and of the ship. Against unannored ships shells with compara- tively thin walls, but containing a largf bursting charge, are used. Against armored ships armor- piercing projectiles are used, if the armor is too thick to be perforated by heavy common shell. To secure greater penetration in hard-faced ar- mor, soft steel caps are placed on shell which are to be used against armor. (See Armob Plate: also Projectile.s.) At close itingc it is possible to select a particular part of a ship for attack: but close ranges are likely to Ijc the exce])tion in naval battles, and many will doubt- less be decided before close range is reached. At long range the probability of hitting at all is not large : therefore it is not advisable to reduce this ])robability by attempting to strike par- ticular parts of the enemy's vessel: all pro- jectiles should therefore be fired to hit the centre of the target it presents. The unavoiilable er- rors will cause the projectiles to deviate more or less from this jioint, but many will hit in places where they will do much damage. Large armor-piercing shells usually have no bursting charges, because gunpowder is not strong enough to burst their thick walls, and very few high- power explosives will stand the shock and heat engendered by passing thrcnigh armor. There are a few powerful cx]ilosives that can be fired through armor: but they are so insensitive that they will not explode of themselves when beyond the armor, and it is dillicult to construct a fuze which will explode them that will not be ignited too soon. The most promising explosives for leading armor-piercing sliells are perhaps jovite and maximite: shells filled with each of the.-e eom])ositions have been fired through armor and satisfactorily exploded beyond. For common shell and armor-piercers not exceeding G inches in calibre, fine black gunpowder is used as the bursting charge. It is safer than any high-power explosive, and can be satisfactorily exploded. Moreover, it breaks the shell into a sufficient number of pieces, and its incendiary effect is be- lieved to be greater than that of any high-power explosive. 'The latter breaks the shell up into very small pieces, which are less destructive than larger ones. The damage caused by the explosion of a shell containing a bursting charge made up of a high-power explosive is very great in the immed'ate vicinity of the explosioin, but the area of destruction is generally less than from shells filled with gunpowder. In former days, if a ship could cross the bow or stern of an enemy and deliver a raking fire, it often caused suiricient destruction of life and material to decide the fight, while the vessel raked could bring few or no guns to bear in re- turn. The value of a raking position has much decreased, and is likely to be further lessened. Recent armored ships are well protected against raking fire, and a very large proportion of their batteries is available against an enemy crossing bow or stern. The different plans upon which the batteries of modern ships are arranged will cause them to try to select such positions with reference to the enemy as will enable them to use their gun power to the best effect, while that of the enemy is less fav(U'ably situated : but if the enemy is sufficiently alert, not even the posses- sion of superior speed will insure that this can 1m> done. The direction of the enemy from a ship is called the angle of presentment, and it is usu- ally measured from the beam; but as regards the striking of shell, the angle of presentment is the angle between the path of the projectile and a normal line or periicndicular to the surface hit. In both old and modern ships the broadside fire is greater than the bow or stern fire; but in modern ships the bow and stern fire is usually strong. With the exception of