GUNS. As a solution of the problem presented by the conditions of firing at great heights and at large angles in order to reach airplanes or balloons, the Krupp firm has brought out three general types of can non, each of which is adapted for a special use. In the first place, there is the more simple type of cannon with field mounting, while a second type is constructed with a view of being placed upon a motor car. For use on shipboard a third type is designed intended to be rapidly rotated in all directions by the use of a central pivot base such as is usually installed on warships for coast-defense use. On the other hand, the field gun has its wheels arranged so as to turn upon pivots, which allows of placing the wheels in crosswise direction. In order to give effective results it is found that the angle of elevation must be at least 70 degrees, and the field gun is designed to reach this angle. The automo bile and ship cannon will, however, make a greater angle, the maximum being for these two types as high as 75 degrees. In all these cases a rapid rate of firing is given by an automatic opening and closing of the breech. The calibre has been reduced as much as possible, as also the weight of the projectile, while the long bore Fives a high initial speed to the shot and dimin ishes the time required to attain the mark. Ow ing to the lessening of the calibre, greater light ness is obtained, and this is of service especially in the field and the automobile types of gun.
Sighting is carried out in the most efficient manner by the use of an appropriate form of sighting telescope in combination with a gen eral finder which covers a wider range of field. There is also•a range-finder by which the dis tance is first obtained, and afterward the indi cations are directly given so as to be able to point the gun for different heights of the air ship without loss of time, and thus the use of firing tables is dispensed with in all these cases.
The question of the kind of shot which is best adapted for firing upon balloons or airships is of prune importance; and this matter has been made the object of a number of experi ments. It is recognized that shrapnel will pen etrate the balloon envelope, but without doing much damage, at least of an immediate nature, seeing that the holes are closed again for the most part by the internal pressure of the gas, so that the loss of gas is not a rapid one and the airship is able to reach a place of safety in the majority of cases. It is found that the most effective form of projectile is a special kind of grenade, which is designed to explode in the interior of the balloon and to bring about ignition of the gas. The projectile designed by the Krupp firm is intended to accomplish this; and at the same time the path of the projectile from the time it leaves the gun can'be followed by the use of a special smoke produced carried on the shot. By observing •the trail of smoke the gunner learns whether the shot comes near the mark When the projectile leaves the gun, the smoke producer has been set working by an appropriate device. At night the path of the shot is still followed by the light which the smoke producer gives out. When it penetrates the envelope, a very sensitive device causes the detonation of the grenade.
In the case of the field cannon, which has a 6.5 centimetre bore (2.6 inches), the weight of the gun itself is 775 pounds and that of the chassis 1,150 pounds, making a total of 1,925 pounds for the cannon when prepared for ac tual service. The gun can be turned about
through a complete circle, and has a maximum vertical angle of 70 degrees. The weight of the projectile for this type is nine pounds. The in itial speed of the shot is 2,050 feet per second. With the field gun it is possible to cover a max imum range of 28,550 feet, and a maximum height of 18,800 feet.
Of a heavier build than the former, and also of greater range, is the second type of gun of 7.5 centimetre (three-inch) calibre, which is designed to be mounted upon a heavy motor car. Like the former, it is provided with hy draulic recoil brake, and in the present case there is used a middle pivot. For elevating and the gun through the required range there is used a double-toothed sector which is driven by pinion and crank. A spe cial arrangement is used for the rotation, by which a slow movement is obtained, but a quick rotation may also be given by the more rapid mechanism when it is needed to turn the gun rapidly into any desired position. It is to be noted that, owing to the high speed at which airships move, such quick movements are one of the features which need to be especially de signed in the case of guns for balloon firing. The weight of the gun itself, 990 pounds, com bined with the weight of the support, 1,550 pounds, gives a total weight of 2;540 pounds for this type of gun. We have here the maxi mum angle which is reached in the Krupp can non, or 75 degrees. The weight of the pro jectile is 12 pounds, and the initial speed 2,060 feet per second. The maximum range is about 30,000 feet, and the greatest height about 20, 000 feet. As regards the automobile car which is designed to take the present cannon, its total weight (exclusive of the gun) is three and a half tons, and it has an average speed of 30 miles an hour.
Owing to the fact that both axles are driv ing axles, with the use of the 50-horsepower motor the automobile car is able to travel over very difficult ground, and it easily mounts very steep grades. Under the front seat is a roomy chest which holds a good supply of tools and extra fittings, and special attention has been given to this point so that the car will not easily become disabled.
The Ehrhardt gun factory of Diisseldorf has also built various anti-aircraft guns, mounted on motor trucks, whose calibres vary from 50 to 105 millimetres. The most remark able of these is the 35-calibre 65-millimetre de sign which fires a 4.1 kg. projectile to a maxi mum height of 5,800 metres with an arc of elevation of 75 degrees and a muzzle velocity of 670 metres per second. This gun can fire three varieties of projectiles: (1) Ordinary shrapnel containing 150 steel balls of 9 grams each; (2) a smoke shrapnel of 170 steel balls of the same weight; and (3) a °balloon gren ade," which is especially adapted for use against airships. This gun is mounted on an armored motor car and weighs complete 6,650 kg. The Skoda Gun Works of Pilzen, Austria, also sup ply an anti-aircraft gun which has a bore of one and a half inches and is 70 calibres long. This gun has a muzzle velocity of 1,000 metres per second and fires a projectile weighing 0.8 kg. at an -elevation up to 80 degrees. It weighs complete 615 kg. and can be mounted on any suitable high-power motor car.