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1210 war high-angle armaments were called for at short notice and in large numbers. There was no opportunity of carrying out prolonged pro- grammes of trials and consequently the ammunition used at first was faulty. Experience improved the material and the methods of using it, and by the end of the war the anti-aircraft guns were a factor to be seriously considered by the aircraft, although the prob- lem at sea remains a very difficult one.

In 1914, a 3-in. Q.F. semi-automatic gun on a mounting capable of 85 of elevation had been completed for the British navy. This equipment, in slightly varying forms, became the chief anti- aircraft gun used in the British service, both ashore and afloat, during the first 3 years of the war. The gun is mounted on a roller- path mounting of the central pivot type, the trunnions being carried high enough to allow the gun to be fired at extreme elevation without the breech fouling the deck on recoil. The semi-automatic gun, with the cartridge and shell fixed together as one element, is used in order to obtain an extremely rapid rate of fire. Several modifications have been made to the original mountings to enable them to be used in small vessels such as destroyers and submarines. In these mountings the sight and the recoil and running-out cylinders are placed below the level of the gun and the mounting itself is simplified and made suitable for submersion in salt water by using non-corrosive metals. The running-out springs of all high-angle mountings have to be considerably strengthened to deal with the increased stresses at high angles of elevation and in some cases pneumatic recuperators are used instead of springs.

At the outbreak of the war, in order to provide a high-angle arma- ment of some sort, a large number of gun mountings was rapidly converted so as to be able to fire at high angles of elevation. Within a few months all important ships in the British fleet were provided with two H.A. guns each, either proper equipments or conversions. The latter were, in no case, satisfactory and they were all replaced by proper H.A. guns as soon as these became available. In 1916 the increased activity of the enemy aircraft, and their more frequent appearance at sea, led to a demand for a larger H.A. gun than the 3-inch. The 4-in. Q.F. gun was brought into use, and was at first mounted on mountings designed for the 3-in. gun, which were suitably strengthened. The 4-in. H.A. Mark II. mounting was eventually introduced for the Q.F. Mark V. gun and this is at pres- ent the standard H.A. armament for all capital ships of the British navy. The mounting is, in general arrangement, a large edition of the original 3-in. H.A. mounting.

The indications are that the size of anti-aircraft guns will tend to increase. The first essential, however, of an efficient anti-aircraft gun is extreme rapidity of fire, and a limit is imposed on the ize of the gun by the weight of the ammunition. A round of " fixed " ammunition for a 4>7-in. gun weighs about 80 Ib. and this is as much as can be handled by one man with any degree of rapidity. It does not appear, therefore, that H.A. guns will increase much above this calibre, unless a complicated power-worked mounting is adopted. The chance of hitting the aircraft must be improved, and the extent of the menace of the aircraft to the capital ship will have to be more clearly defined before it can be anticipated that this step will be taken by any navy.

Fire Control. The installation used for the control of the gunfire of warships had become increasingly intricate in the years before the war, and the experience gained during the war has made the addition of further complications necessary. Little can be said as to the details of the many instruments used, as the majority of them are confidential, and the functions, and even the existence, of some of them are kept as secret as possible. All nations are very reticent as to the actual systems employed in their ships. But the main prob- lems are the same for all, and can be considered in 3 divisions: (i.) the communications between the control stations and the guns, (ii.) the apparatus for obtaining the range and deflection and keeping them both correct, (iii.) the arrangements for firing the guns and observing the fall of the shot. These 3 sections must work in unison to form a perfect organization, and the system that is em- ployed to make them do so must be able to withstand the stress of action conditions without breaking down. The methods employed to attain this are kept secret by all navies, and these methods are continually being altered and improved in detail, as the result of experience gained in practice and by the invention of new apparatus. In the following paragraphs a brief outline will be found of the principal instruments used in each section.

Communications. The positions between which communication must be maintained are the observing positions aloft, the principal control position, which is usually in the vicinity of the conning tower, the turrets or other gun positions and the transmitting station. Com- munications must be rapid and sure as most of the information sent is only of value at the moment of transmission and loses its signifi- cance if any delay occurs. Hence several lines usually exist between important stations, any of which can be instantly used in the event of breakdown in the others. All lines of communication are usually concentrated from the outlying stations into the transmitting station. This station is situated in the centre of the ship, below the armoured deck, in the quietest position that can be selected and it forms the centre of the whole control organization.

Voice pipes are used to a great extent between stations that are permanently manned and are moderately clse together. Their

acoustic, properties, however, become poor when the distances are increased beyond certain well-defined limits for each diam. of pipe or when there are bends in the lead of the pipes. Voice pipes are also difficult to make watertight or gastight.

The telephone is generally used between all stations, often in addition to the voice pipe. There is usually a telephone exchange, either in or near the transmitting station, for the sole use of the fire-control organization and independent of the general telephone system of the ship. Between important stations direct telephones, not connected to the exchange, are sometimes used. The actual transmitters and receivers are of many patterns, specially designed for operators who have other duties to perform or who may have to use the instruments in positions exposed to the weather. Electro- mechanical transmitters and receivers are used for passing range, deflection, bearing, orders and other information of a standard character between the control positions and the guns. There are several different patterns of these instruments, the most commonly used being the Barr and Stroud " step by step " and the Vickers " counter " types, both of which are in use in the ships of all navies. Frequently, with both these types a single transmitter is arranged to work a number of receivers in outlying stations and the uses to which the instruments can be put are manifold. A development of these instruments is found in the " follow the pointer " method, which is commonly used for transmitting ranges from the trans- mitting stations to the guns. Here the transmitter is in the form of a sight dial upon which the desired range is set by moving a pointer to the required setting. The motion of the pointer is transmitted electrically to a pointer on the gunsights. A mechanical pointer, geared to the mechanism which works the sight, is kept in line with the electric pointer and the sight is thus kept set without the sight- setter having to watch the movements of a separate instrument. This greatly simplifies the work of the sight-setter and eliminates errors. The large clock-faced dials and other similar arrangements that are often seen about the upperworks of warships are used for communicating the range and deflection in use to consorts who may be firing at the same target. Their place will probably be taken in the future by wireless telegraphy or telephony.

Range Finding and Keeping. The transmitting station forms the centre of the whole control organization. In it are situated the majority of the calculating instruments, and through it are passed all the orders from the control officer to the guns. The functions of the majority of the instruments in the transmitting station and their details are, naturally, confidential. Broadly, they consist of arrange- ments for deducing the course and speed of the enemy from such data as may be available, and for calculating from this the change of range and deflection that should be applied to the gunsights. In the British service a calculating table, invented by Capt. F. C. Dreyer, is in general use, and to this improvements are continually being added to meet the changed conditions brought about by the increasing range at which the guns are used. The principles upon which this table is worked are secret, but there are other sets of apparatus, notably the Argo and the Ford, which have been patented and which aim at achieving the same results. Apart from the calculating apparatus, some form of which is in use in all navies, there are certain instruments employed generally for obtaining the required data, and a few of these can be mentioned.

Range- Finders. The range-finder most commonly used in all navies is the Barr and Stroud coincidence instrument which has been in existence for a number of years (see RANGE-FINDERS). In the British navy this instrument proved its value during the war. To obtain greater accuracy at long ranges the length of the base of the range-finder has been increased from the original one metre to as much as 30 ft. The one-metre instrument is now employed only for navigational work and a 45 or g-ft. instrument is used in destroyers and other small ships. In light cruisers 9-ft. and 12-ft. instruments are used, and the 15-ft. instrument is in general use in capital ships. In some of the latest ships the base length has been increased to 30 ft., these instruments being usually mounted in turrets. The Barr and Stroud range-finder has been found to give generally satis- factory results, and any man with normally good eyesight can be trained to obtain accurate observations with it. In this it has a great advantage over the range-finders constructed on the stereo- scopic principle, as used in the German and in some other navies.

To use one of these instruments it is necessasy for the observer to have stereoscopic vision, a rare gift and one which varies in quality from day to day. A range-finder constructed on the sextant prin- ciple (Waymouth-Cooke) has been used to a considerable extent in destroyers. The instrument is small and handy, but the results obtained have been far from accurate and it is being superseded by the short-base Barr and Stroud instrument. At present there are at least 6 range-finders mounted in a capital ship for the use of the gun- nery control, and this number is reduced proportionately in the light cruisers and smaller ships. In a capital ship one instrument is mounted in each turret and 2 others in positions aloft or above the level of the guns. The results of the observations of all the instru- ments are transmitted electrically to the transmitting station, where apparatus exists for rapidly obtaining a mean of the observa- tions, thus giving what is called the " mean range-finder range." To this it is necessary to apply corrections for the density of the air, the effect of wind, the temperature of the charges and the nature of the