Page:Encyclopædia Britannica, Ninth Edition, v. 11.djvu/321

Rh GUNNERY 305 .fe &amp;lt;2 / % 1 1 C$ Fio. 18. Palliser shell. greater thickness, but the damage done by the fragments of the Palliser after perforation is more serious. The cost of the steel shell is about five times that of the iron ones. The bodies are cast in sand, because extreme hardness is not tkere required, and a sounder casting is thus obtained. No fuzes are used with these shells ; they are burst by the shock of impact on armour which explodes the powder charge. It is doubtful if they would explode on striking iron vessels not armour-plated, and they would fail to burst on striking wooden ships. They are effective in destroying masonry, and have been driven through great thicknesses of stone. They hold about a quarter as much powder as common shell of the same diameter. The greatest pene tration of armour yet known was obtained by the 80-ton gun at Shoeburyness in 1877. The target consisted of four 8-inch wrought-iron plates, sandwiched with three 5-iuch layers of teak, the whole put to gether with immense strength. The pro jectile perforated three plates and the teak, digging its nose about half-way into the last plate, which was much cracked and bulged. The 100-ton gun has perforated with ease 22 inches of solid wrought iron plate strongly backed, but failed to drive a hole through a similar target when the plate was of steel. Very recently extraordinary penetration has been obtained by a 6-inch 70-pouncler made by Sir W. G. Armstrong & Co. Fired with a velocity of nearly 2000 f. s., this small projectile pierced about 11 inches of wrought iron. The subject of penetration is treated under GUNMAKING. A description of some of the fuzes and firing tubes used in gunnery will be found under AMMUNITION. The general principle guiding the selection of time or percussion fuzes is that when a shell is required to burst in the air a time fuze is employed, when on striking an object a percussion fuze is chosen. In muzzle-loading guns (not using gas- checks), time fuzes are ignited by the flash of discharge ; otherwise the shock is taken advantage of to light the coin- Fuzes, position by exploding a detonator. Percussion fuzes are sometimes found to act too rapidly; where it is desired that penetration to a certain depth in earth or other material shall take place before explosion, it is found necessary to slow the fuze by interposing a small column of composition, burning for, say, a quarter of a second, between the deton ator and the bursting charge. In firing a heavy shell with nig 1 ! velocity at a weak vessel, the resistance of the side is so slight that it may happen that the fuse either fails to act (the shell not being sufficiently retarded to set it in action), or explodes the shell after it has passed through both sides. To meet this case a specially sensitive and rapidly-acting fuze has been devised. Guns were formerly primed with loose powder and fired by a match, next by common quill tubes filled with com position and ignited by a portfire, then by detonating tubes exploded by a hammer. Now friction tubes have superseded these methods for ordinary service. When it is desired to fire a gun from a distance, or to fire a number Electric of guns absolutely at the same moment, Abel s electric tubes are employed. In them two fine copper wires pass down through the head, insulated by gutta percha, except at the ends, which are separated by y^th of an inch of a composition of subphosphide and subsulphide of copper with chlorate of potash. The other ends of the wires are in contact with the copper lining of two holes in the head. The wires from the battery are placed in these holes ; when the current passes, the composition is heated to ignition and explodes the tube. Service of Ordnance. The general principles guiding Ihe tubes. employment and manipulation of artillery are applicable to the schemes of warfare of all civilized nations. Slight differences exist in calibres and weights ; but it may be taken that the considerations which regulate the service of English guns have the same force elsewhere. The details of manufacture, the systems of loading, and the methods of rilling, are the chief points regarding which artillerists differ ; these matters are treated under GUNMAKIKG. Of two pieces constructed with equal skill to perform the same kind of work, the heavier will always be the more powerful. Thus weight is the chief controlling element in the employ ment of guns, though cost and convenience of manipulation have often to be taken into account. The artillery of the present day is the outcome of a long series of improvements, and the whole system of this important arm bears traces of frequent modification and continual compromise. The first introduction of firearms appears to have taken place in England in the reign of Edward III. On the Continent it was probably somewhat earlier, but the actual date and the circumstances attending their introduction are involved in obscurity. It is said that cannon were used in the English expedition against Scotland in 1327, and at the battle of Crccy in 1346. In 1360 there were four copper guns in Earl the Tower. For about two centuries cannon continued to orcu: be manufactured of copper, brass, or bronze, good castings of which were made long before the art of smelting iron ores was perfected. In the early part of the 16th century guns were sometimevS made of wrought iron plates put together longitudinally and hooped with wrought iron. In 1545 cast iron ordnance were manufactured in England, and supplanted pieces of all other materials for a time. The growing needs of warfare, however, soon demanded guns possessed of fair mobility to accompany armies in the field, and the cast iron pieces used being found excessively cumbrous, bronze was once again resorted to for field artillery. From about the middle of the 17th century till the introduction of rifled cannon, all the heavier natures of ordnance fortress, siege, and ship guns were made of cast iron ; and all the lighter field and boat guns of bronze. In 1717 the bronze foundry was established at Woolwich, and most of the smooth-bored field pieces, howitzers, and mortars used in the service were made there. The heavy cast iron guns were supplied by contractors, and proved by Government officials. The long peace which suc ceeded the Napoleonic wars was highly unfavourable to the progress of gunnery, but a great development took place in the arts and sciences, so that, on the breaking out of the Crimean War, the latest discoveries in metallurgy and the excellence attained in machinery at once enabled inventors to make a great advance in artillery. At the transition period, a few wrought iron smooth-bores, throwing spherical shot of 150 and 100 R), were manufactured to overcome the resistance of iron plates then recently introduced for armour ing ships. These pieces were speedily discarded for rifled guns; and practically it may be said that the adoption of steel and wrought iron for guns coincided with .the change from smooth-bores to rifles, both steps of progress being thoroughly established about 1860. In spite of the great superiority of the new ordnance, it cannot be said that the old pieces are yet superseded ; vast numbers of them exist over all parts of the world, and often form the only defence. Even the fortifications in England are still largely armed Sm&amp;lt; with them on land fronts ; and though they are gradually k ri disappearing, they yet claim notice. Bronze guns are now orj: obsolete in the British service. Figs. 19 to 24 show typical kinds of cast iron ordnance. Those denominated acccording to the weight of their projectile are made strong enough to fire solid shot or shell ; those called by the diameter of tho bore fire shell only. It must be remembered that, with spherical projectiles, the solid must be heavier than tho XL _ 39