Page:Encyclopædia Britannica, Ninth Edition, v. 11.djvu/326

Rh 310 GUNNERY somewhat similar to Palliser projectiles, for penetrating masonry ; also with common and shrapnel shell. The howit zers rarely use shrapnel shell. On first attacking a fortress at a long range, the duty of the guns is to cut down the defender s parapets, dismount his artillery, dismantle his ramparts, and subdue his fire, so as to facilitate the con- FIG. 32. 8-inch Howitzer, 46 cwt. (section). stmction of batteries nearer the place. In the meanwhile ths howitzers lob heavy shell into his works, and bombard the town, if necessary. As soon as practicable, breaching batteries are thrown up in such spots as may be found suitable for the attack of a weak point. It is rarely possible to breach by direct fire in the case of works of modern Fio. 33. 8-inch Howitzer (section of groove). design. Here it is that curved fire is so effective, and here it is that the accuracy of rifled howitzers becomes so neces sary. In order to make a practicable breach up which an assault can be delivered, the masonry at B (fig. 34), must be cut away, and owing to the height of the cover at A the fire must be curved to reach a point sufficiently low. Direct fire tir a plein fouet, as the French express it would strike too high up. Sometimes a work is so constructed that it is necessary to strike a point half-way down the masonry revetment to form a practicable breach. As it is desirable Breach- to strike with as much force as possible in breaching, it is i n o- evident that where the profile of the work requires the angle of descent of the shell to be considerable, it is necessary Fio. 34. Profile of Work. to select a spot for the battery at the longest range com patible with accuracy. For, given a certain angle of descent, the longer the trajectory (ccet. par.} terminating in that angle, the greater will be the remaining velocity. Sometimes the guns of the siege train are employed with an army in the field to hold certain valuable ground against attack. They are then called guns of position, and are so placed as to com mand the approaches most effectively, and yet, if possible, to be dragged away at the last moment in case of retreat. They will usually fire shrapnel shell when thus employed. 4. The all-important qualities of field guns (figs. 35, 36, 37) are mobility and shrapnel -thro wing power. They must be able to make long marches rapidly, to change position with celerity, to crush troops and the enemy s artillery with accurate, well-sustained fire at high velocities, and to support rough usage without detriment to their efficiency. They are supplied with shrapnel and common shell, and case shot, of which shrapnel form by far the largest proportion. 5. T:iz mountain-train guns are both 7-pounders; they fire Mom the same shell, but the heavier one uses a 12-oz. cartridge, taia while 6 ounces is as much as can be fired from the lighter S unSi rr.-.-i- 84 . LENGTH OF BORE FIG. 35. 13-pounder of 8 cwt. (section). one. Both guns are intended for mule transport, one mule taking the gun, another the carriage, and a third the wheels, &c.; but at the Cape of Good Hope the heavier 7-pounder is mounted on a light high field-carriage for transport as well as for firing, while in Ashantee the lighter 7-pounders were dragged on a kind of sleigh. The lighter gun is tolerably effective for nearly a mile, and the heavier for about a mile and a half. Some jointed guns, proposed by FIG. 36. 13-pounder of 8 cwt. (front view). FIG. 37. 13-pounder of 8 cwt. (section of groove). an artillery officer, are now under trial. They are composed of two pieces screwed together, and, being carried separately, form a gun of about twice the weight of the ordinary mountain gun. Great increase of power is expected from this method of construction. Mountain guns are principally employed to throw time-fuzed shrapnel at troops, and per cussion-fuzed common shell into hill works and woods occupied by the enemy. In Table V. the principal sea-service rifled guns are shown. Nava Three kinds of work are performed by them, viz., to pierce g !ls - ironclads and armoured forts, to attack unarmoured vessels, and to keep up a fire on troops on shore or on approaching boats. The heavy armour-piercing guns are well provided with common shell, as well as with chilled projectiles, so as to perform the first and second duties, but they have a very small proportion of shrapnel shell, which is intended to be used by them against troops or boats only on emer gency. The 7-inch and G4-pounder guns are supposed to be quite sufficient in ordinary cases for the second and third duties, assisted in the third case by the smaller boat guns. All these are well furnished with common shell and shrapnel. Gun Carriages. The development which has taken Cam. place of late years in the power of artillery has necessitated corresponding changes in gun carriages. Formerly, every carriage was capable of travelling to some extent ; even the heaviest guns were mounted on carriages fitted with trucks, which permitted motion on the ramparts or about a deck. Later on, sloping traversing platforms were intro duced, up which the gun carriage recoiled on firing. Extra means of checking recoil became necessary as the power of the guns grew ; compressors, or friction plates, were introduced, and are now only partially superseded by the hydraulic buffer. Mobility of carriage has almost entirely been given up, except for field and mountain artillery. The heavier siege guns travel on platform waggons, not on their firing carriages ; and it is possible that the traversing plat form and slide principle will extend yet further. Tables IV. and V. show how the various pieces in the British service are mounted. Differences of detail exist, but the general system is the same for all European