From experiments made in France it was ascertained that hollow shot, being with equal weight greater in diameter than such as are solid, when fired with low charges of powder against ships, pro duced most dangerous breaches in their sides; and, in consequence, certain heavy iron howitzer-guns for discharging such missiles were introduced in the French navy. Similar experiments, attended by like results, were in 1828 made in this country by the late General Millar, with a short and massive 12-inch gun which he invented on the occasion. The hollow shot projected from this piece of ordnance weighed 120 !pounds, and being impelled by 11 pounds of powder, producing au initial velocity of 1000 feet per second, it pierced, at the distance of 400 yards, a strong frame-work of timber, making an opening which would have seriously compromised any ship so struck. A conviction of the necessity of using these powerful arms in a future war led the British government to adopt 8- and 10-inch guns in the royal navy, and now the ships of war always carry a certain number of such guns.
Various experiments were made in France, England, and America, on the effect of shells fired into and exploded in ships, the fuses being cut of such a length as to explode the shell after striking ; or, still Letter, by means of concussion fuses. The destructive effects were so great that shells and shell guns were at once adopted in the navy, and form a large portion of the armament, though the existence of loaded shells on board of ships has been objected to on account of the danger which might ensue from the accidental ignition of their fuses. This danger, however, may be much lessened by keeping each shell in a separate box, and by covering the fuse with a metallic cap till the moment when it is required to be put in the gun.
The carriages for guns vary much according to the calibre of the gun and the objects to which they are to he applied, or the mobility required.
The field gun carriage, in which great lightness and mobility com bined with strength are required, is composed of one large solid piece termed the trail, to which two small brackets are attached, one on each side. The trail rests at one end on the axletree of a pair of high wheels. The tninnion holes are cut in these brackets : as it is necessary to come into action very rapidly there is only one set of trunnion holes in a field gun carriage, and they are placed far back on the carriage over the rear of the axletrec, which has been found to be the best position both on account of the reduced strain on the carriage when fired, and of the ease with which the trail can be lifted to limber up or unlimber the gun. When the gun is in action the rear extremity of the trail rests on the ground, but when it is required to Le moved, the end of the trail which is fitted with an eye is raised and placed on a hook in the limber.
The limber is a bed, with shafts, mounted on two wheels, and carrying two ammunition boxes for the service of the gun ; the horses are harnessed to the limber, and the gun with its carriage is drawn after the latter. An ammunition waggon also accompanies each piece of ordnance, and there are others always in reserve.
Field howitzer carriages and their limbers are similar to those just mentioned, but stronger.
Carriages of a light construction are employed for the small artillery which is used on service in mountainous countries.
The travelling carriages for siege-ordnance are made wholly of oak, amp the limber carries no ammunition ; the great size and weight of the gun-carriage trail not permitting, when it rests on the limber, the boxes to be placed there. The trail of siege-carriages is made of two cheeks or side pieces firmly attached together by means of transoms, and resting on the axletree of the wheels, instead of in a single piece or block trail, as with field gun-carriages.
Carriages for garrison service and for the navy consist of two short cheeks or brackets, connected by transoms, and they move on four truck-wheek Garrison carriages are now often made of cast-iron, which is more durable than wood, particularly in tropical climates. Iligh platform,' of timber or cast-iron arc also occasionally placed at the salient angles of fortresses ; they are made to turn at one extremity upon a vertical pivot, the other extremity-traversing through ninety or a greater number of degrees. The usual garrison carriage is mounted upon this platform, and thus the piece can he fired over the parapet in any direction at pleasure. There is also a species of mounting for guns, termer; a traversing platform, by means of which the gun may be made to pivot on any centre, and be directed with great ease in various directions. Traversing platforms are principally used for heavy guns, 68-pounders, and 8- and 10-inch guns on board ships and in casemates.
Mortara are placed upon solid beds of wood or iron, which are made as heavy as is consistent with the power of transporting them from place to place, and for the sake of obtaining steadiness when the piece is fired. The larger kinds of mortars and their beds are removed on platform carriages. Sea mortar-beds are made of strong timber •, they have a hole in the middle for receiving the iron bolt on which the bed turns round, and they are placed on strong wooden frames fixed in the vessels by which they are carried.