Gunpowder, however, after a reign of more than five hundred years, has been dethroned. The “villainous saltpetre” of the monk, with its allies, charcoal and sulphur, yields now to nitro compounds, which produce not only far greater energy, but are as well smokeless. The sea-fights of our war with Spain saw the last contending fleets to be wrapped in a cloud, lingering and baffling, of their own making. Cordite, one of these compounds in use abroad, is prepared in long “cords” from di-nitro-cellulose and nitro-glycerine. The new smokeless “powder” of the United States navy is made from nitro-cellulose dissolved in ether alcohol. France was the first in employing explosives such as these, which, in their offensive and tactical advantages, form one of the signal triumphs of the century’s last years.
The long gun of modern days is of necessity breech-loading. The development of other elements gave, as a resultant, great length; and this, in turn, required a system of charging which would permit protection for the men while loading, and would obviate the intolerable inconvenience of ramming home powder and shot in a long muzzle-loader—an operation which was, in fact, impossible beyond a certain limit of length. The advocates of the older construction, especially in England, urged long and earnestly its simplicity and the superior strength of a solid breech; but the logic of events was against them, and the breech-loader won a complete triumph. It is worthy of note that it, like rifling and the principle of building up, was but a revival. From the warship Mary Rose, sunk in 1545 in action off Spithead, there were recovered in 1836 a number of guns, some of which are of wrought iron, built-up and breech-loading. There are in use two methods of closing the breech when the gun is loaded from the rear. In French, English, and American ordnance an axial screw-plug is inserted; in the Krupp system a cylindro-prismatic breech-block slides in a horizontal opening cut across the bore. The former, or interrupted screw mechanism, was first set forth in the United States’ patent of 1849 to Chambers.
In projectiles the tendency of the modern era has been towards simplification. Bar-shot, chain-shot, and grape have disappeared, while canister and solid shot are becoming obsolete. There remain shrapnel as the “man-killer” of this age, and explosive shell, differentiated into armor-piercing and that for attack on unarmored structures. Lieutenant Shrapnel, in 1796, invented the projectile which bears his name. In its modern form, it consists of a steel case containing lead or iron balls and a light bursting charge of powder, ignited by a time-fuse carried in the head. This projectile is most formidable against bodies of men, boats, and the embrasures of forts, since, when it is ruptured, the balls are dispersed, covering a wide area.
The use of explosive shell in high-angle discharge dates back to the fifteenth century. From Paixhans’ works, “La Nouvelle Arme,” published in 1821, came the stimulus to its development and to its deadly service, in our time, in horizontal fire. The “common shell” for the United States 13-inch rifle is made of forged steel, weighs 1100 pounds, and carries within it a bursting charge of 50 pounds of powder, ignited by a percussion fuse set in its base. It will penetrate 6 or 7 inches of armor and then explode within the ship. The United States “armor-piercing shell” is manufactured from crucible steel, alloyed with chromium; it is tempered to extreme hardness at the point, which carries a cap of soft metal. The function of the latter would appear to be that of a support to the shoulder of the projectile, or as a lubricant thereto, since, without the cap, the shell is broken or deformed in the attack on armor of surface hardened steel. To resist the crushing strain in its passage through massive plate, the walls of this shell must be so thick that no charge of gunpowder will burst it. Hence, as a rule, the shell is fired unloaded, although recently there have been adopted to some extent bursting charges of some high explosive, such as gun-cotton, joveite, or picric acid.
In closing this brief review of the progress of ordnance, but passing mention can be made of matters minor, but in themselves of much importance. Gun carriages, or mounts, are now intricate mechanisms, practically the whole service of large ordnance being performed by electric and hydraulic machinery. The rapid fire principle has been extended to pieces of 6-inch calibre, and bids fair to pass beyond that limit. Its success in increasing largely the number of shots within a given time lies in special breech-blocks, aiming devices, and prepared cartridges. Machine guns of rifle-calibre, partly or wholly automatic, have been so developed as to be capable of firing 1200 rounds per minute. The discharge of high explosives in large quantity was effected with success by the United States steamer Vesuvius off Santiago. The torpedo-gun afloat, however, would appear to be still in a tentative condition.
A brief lapse into technical terms may be permitted in summarizing the gun’s growth in power. The term “muzzle energy” is used to describe the work which the projectile is capable of performing when it leaves the bore. It is expressed in foot-tons, i. e., the number of tons which the energy stored in the shot would lift to a height of one foot. The figures as to this for the 32-pounder of the century’s beginning, for the United States 13-inch rifle and for the 111-ton English gun, are, respectively, 642, 33,627, and 54,690 foot-tons. Again, the round shot from the 32-pounder lost from the resistance of the air, in a range of 1200 yards, 76 per cent of its energy; while this loss, with the United States 13-inch, in a range of 1000 yards, is but 11 per cent. Finally, if the cast-iron shot of the 32-pounder were fired against armor-plate, it would lose, in breaking itself up, two thirds of its remaining energy, leaving at 1200 yards but 51 foot-tons for effective work; while with the modern armor-piercing shell the entire energy left at the end of the range is expended upon the armor-plate.
It will be seen then that the immeasurable superiority of modern guns is owing both to their great increase in energy and to their wiser disposition of that which has been attained. The gun has maintained fully during the century its primacy among naval weapons. It is true that, in theory and on paper, its supremacy has at times been questioned; but as to its two rivals, the ram would seem to be rather the weapon of accident than action, and the torpedo has yet to score in battle against ships in motion, while the precision, rapidity, and power of the gun grow more deadly with every passing year.
VI. THE DEVELOPMENT OF ARMOR.
Armor and the gun are natural and now hereditary foes. The function of the one is to resist, that of the other ever to attack. Since the beginning of the modern era in navies, there has been ceaseless strife for mastery between these two elements of warship design, the gun ever becoming more powerful, and the armor—at first through growing thickness and later through improved material—opposing a steadily more stubborn front. The official report of an English committee made in the year 1860 states that,—
“Vessels clothed in rolled-iron plates of four and a half inches’ thickness are to all practicable purposes invulnerable against any projectile that can be brought to bear against them at any range.”