(a) CAVALRY PORTABLE WIRELESS CART SET.
By permission of
Marconi Co. Ltd.
(b) AEROPLANE FITTED WITH WIRELESS TELEGRAPHY.
The rapid development of aviation during the past few years has drawn attention to the necessity for some means of communication between the land and airships and aeroplanes in flight. At first sight it might appear that wireless telegraphy could be used for this purpose without any trouble, but experience has shown that there are certain difficulties in the way, especially with regard to aeroplanes. The chief difficulty with aeroplanes lies in the aerial. This must take the form either of a long trailing wire or of fixed wires running between the planes and the tail. A trailing wire is open to the objection that it is liable to get mixed up with the propeller, besides which it appears likely to hamper to some slight extent the movements of a small and light machine. A fixed aerial between planes and tail avoids these difficulties, but on the other hand its wave-length is bound to be inconveniently small. The heavy and powerful British military aeroplanes apparently use a trailing wire of moderate length, carried in a special manner so as to clear the propeller, but few details are available at present. A further trouble with aeroplanes lies in the tremendous noise made by the engine, which frequently makes it quite impossible to hear incoming signals; and the only way of getting over this difficulty appears to be for the operator to wear some sort of sound-proof head-gear. Signals have been transmitted from an aeroplane in flight up to distances of 40 or 50 miles quite successfully, but the reception of signals by aeroplanes is not so satisfactory, except for comparatively short distances. Although few particulars have been published regarding the work of the British aeroplanes in France, it seems evident that wireless telegraphy is in regular use. In addition to their value as scouts, our aeroplanes appear to be extremely useful for the direction of heavy artillery fire, using wireless to tell the gunners where each shell falls, until the exact range is obtained. In the case of airships the problem of wireless communication is much simpler. A trailing wire presents no difficulties, and on account of their great size much more powerful sets of apparatus can be carried. The huge German Zeppelin airships have a long freely-floating aerial consisting of a wire which can be wound in or let out as required, its full length being about 750 feet. The total weight of the apparatus is nearly 300 lb., and the transmitting range is said to be from about 120 to 200 miles.
Electricity is used in the navy for a great variety of purposes besides telegraphy. Our battleships are lighted by electricity, which is generated at a standard pressure of 220 volts. This current is transformed down for the searchlights, and also for the intricate systems of telephone, alarm, and firing circuits. The magazines containing the deadly cordite are maintained at a constant temperature of 70° F. by special refrigerating machinery driven by electricity, and the numerous fans for ventilating the different parts of the ship are also electrically driven. Electric power is used for capstans, coaling winches, sounding machines, lifts, pumps, whether for drainage, fire extinction, or raising fresh water from the tanks, and for the mechanism for operating boats and torpedo nets. The mechanism for manipulating the great guns and their ammunition is hydraulic. Electricity was tried for this purpose on the battle cruiser Invincible, but was abandoned in favour of hydraulic power. But though electricity is apparently out of favour in this department, it takes an extremely important share in the work of controlling and firing the guns; its duties being such as could not be carried out by hydraulic power.
The guns are controlled and fired from what is known as the fire-control room, which is situated in the interior of the ship, quite away from the guns themselves. The range-finder, from his perch up in the gigantic mast, watches an enemy warship as she looms on the horizon, and when she comes within range he estimates her distance by means of instruments of wonderful precision. He then telephones to the fire-control room, giving this distance, and also the enemy’s speed and course. The officer in charge of the fire-control room calculates the elevation of the gun required for this distance, and decides upon the instant at which the gun must be fired. A telephoned order goes to the gun-turret, and the guns are brought to bear upon the enemy, laid at the required elevation, and sighted. At the correct instant the fire-control officer switches on an electric current to the gun, which fires a small quantity of highly explosive material, and this in turn fires the main charge of cordite. The effect of the shell is watched intently from the fire-control top, up above the range-finder, and if, as is very likely, this first shell falls short of, or overshoots the mark, an estimate of the amount of error is communicated to the fire-control room. Due corrections are then made, the gun is laid at a slightly different elevation, and this time the shell finds its mark with unerring accuracy.
The range of movement, horizontal and vertical, of modern naval guns is so great that it is possible for two guns to be in such relative positions that the firing of one would damage the other. To guard against a disaster of this kind fixed stops are used, supplemented by ingenious automatic alarms. The alarm begins to sound as soon as any gun passes into a position in which it could damage another gun, and it goes on sounding until the latter gun is moved out of the danger line.
Since the outbreak of war the subject of submarine mines has been brought to our notice in very forcible fashion. Contrary to the general impression, the explosive submarine mine is not a recent introduction. It is difficult to say exactly when mines were first brought into use, but at any rate we know that they were employed by Russia during the Crimean War, apparently with little success. The first really successful use of mines occurred in the American Civil War, when the Confederates sank a number of vessels by means of them. This practical demonstration of their possibilities did not pass unnoticed by European nations, and in the Franco-German War we find that mines were used for harbour defence by both belligerents. It is doubtful whether either nation derived much benefit from its mines, and indeed as the war progressed Germany found that the principal result of her mining operations was to render her harbours difficult and dangerous to her own shipping. Much greater success attended the use of mines in the Russo-Japanese War, but all previous records shrink into insignificance when compared with the destruction wrought by mines in the present great conflict.