With the armor trials for the plating of the batteries used at Kinburn, in which the superi ority of the solid plate was shown, the steady de velopment of armor commenced. Before the appli cation of armor to sea-going ships, which began with the Couronne and Ii/oire, time investigation of its qualities naturally lacked impetus, but heneeforward its improvement was steadily sought, and its manufacture soon became a sepa rate industry. The quality of the early plates was very poor. showing lack of facilities for manufacture and experience in producing pure and homogeneous metal and in working it. This condition of a ffairs was speedily altered; heavy hammers and rolls were rapidly brought into use, and by 1562 the manufacture of homogeneous wrought-plate was brought to the highest state of perfection, both in England and France. In the meantime gun and projectile makers had not been idle. The 32-pounder and OS-pounder smooth bores using solid cast-iron projectiles were the standards for armor testing: the S-inch, fl inch. and 10-inch shell guns were brought out long before the application of armor to sea going ships. but shells from these guns were too light, and the shot of too low velocity, to render them superior to the longer pieces mentioned.
Rifled guns began to be used commonly about 1560; France, Prussia, and Russia adopted them in 1858, the two latter deciding upon the breech loader. France retained the muzzle-loading sys tem until 1864; the (Mire was armed with a battery of muzzle-loading rifles in 1859, though her designed armament consisted of smooth bores. In 1855 Armstrong brought out a breech loading piece of small calibre, and Whitworth submitted to the Government in 1856 designs for breech-loading and muzzle-loading guns of all calibres. The Armstrong system was adopted for use in the British Navy, but repeated acci dents led to an outcry against the breech-loading system, and in 1863 the Committee on Designs for Artillery conducted experiments with muzzle loading guns which led to the adoption of the Woolwich type of muzzle-loader. But whether breech-loading or muzzle-loading, the guns were all rifles, and the increased penetrative power ren dered all armor so far produced easily vulner able. The armor makers endeavored to meet the new situation in various ways. The thickness of the plate was increased; steel plates of various kinds were tried, as were plates made up of layers of steel and iron. The steel plates resisted perforation better than wrought iron, but were so easily cracked and destroyed that they failed to gain favor. Whitworth, always in the van in the development of ordnance, made and used forged steel projectiles in 1862. but their value was not generally realized, because the soft iron armor then in vogue was equally penetrable by the east-iron shot. As the thickness of the wrought-iron plate increased, the difficulties of its manufacture grew rapidly. Neither rolls nor hammer could successfully handle the thickness demanded by ship designers. Resort was had to welding, but this was not satisfactory; first, because it could not be effectively done except by machining the faces to be joined, which added greatly to the expense; and secondly, because even then the weld was usually imperfect. The
next step was to 'sandwich' several plates with a layer of wood between them. The result was found to be inferior to that obtained from a sin gle plate, but the plan was for a time accepted as the best available one. In 1866. Grnson in Germany and Palliser in England brought out cast-iron shell with hard, chilled points. These further increased the penetrative power of the gun.
The question of the backing of armor received attention from time to time, and the results obtained are interesting even now. With the low velocities in use up to 1880. wood-backing played a very important part, but its importance has diminished in recent years: all thick armor is still backed with wood, but its thickness is about a quarter of that considered desirable in the days of wrought-iron plate. The backing of the Warrior's 4.5-inch armor was of teak, 20 inches thick, in two layers of 10 inches each. A less thickness of backing and 5 inches of armor gave inferior resistance to penetration. As projectiles improved in quality and acquired greater ve locity, the advantage of thick backing was less apparent ; indeed. except for the purpose of re ducing the shock to a ship 's framing it is now regarded as disadvantageous, for the same weight added to time plate to increase its thickness will give greater resistance to penetration.
Notwithstanding the confessed weakness of homogeneous wrought-iron plate, a successful competitor was long in coining, though both compound and steel plates early appeared in the competition, as has already been stated. In 1359 the Mersey Works in England submitted 2.5-inch plates made up of three layers, the outer ones of wrought iron welded to a middle one of steel: the welding was imperfect and the brittle ness of the steel affected the outer layers: more over, they were constructed on a wrong principle, as will he seen presently in connection with capped projectiles. In 1861 compound and steel plates were tested in England ; while a long series of tests with steel was carried on in France from 1S57 to 1361. The theoretical ad Nantages of steel and compound armor were thoroughly understood at this time, hut brittle ness defeated one and imperfect welding com bined with brittleness precluded the use of the other. The preeminence of wrought-iron plate continued practically undisputed until 1S76. In 1875, the Italian Government called for test plates of 22-inch solid armor from all the prin cipal manufacturers in the world. Four re sponded—Brown & Co. submitted two solid iron plates; Cammell & Co. one solid plate and one sandwich target; Harrell et Cie. presented the same: and Schneider et Cie. presented for test two solid steel plates. The trials took place at Spezia in 1876, and the re sult was overwhelmingly in favor of the steel plates; though these cracked more than the others, the difference in resistance to penetra tion was great. As a result of the Spezia test, wrought-iron plates were hilly discredited. In England, where the prejudice against steel was fostered to sonic extent by national jealousy of a French manufacturer's success. compound ar mor was rapidly developed. This consisted of a Bard steel face welded to a wrought-iron back.