Stevens, in the course of his experiments, made the important discovery, that a single plate of boiler-iron, five-eighths of an inch in thickness, and weighing less than twenty-five pounds to the superficial foot[A], when nailed to the side of a ship, was impenetrable by shell and red-hot shot, the two missiles most dangerous to wooden walls. When a solid shot strikes the side of a wooden ship, it passes in and usually stops before it reaches the opposite side. The fibres of the wood yield and close up behind it, and it often happens, from the reunion of the fibres, that it is difficult to find the place perforated by the ball, and if found, it is often easy to remedy the injury by a simple plug. But if a red-hot shot enter the ship, it may imbed itself in the wood or coils of cordage or sails, or reach the magazine, and thus destroy the whole structure, while the shell may explode within the ship and carry destruction to both men and vessel. If, then, the iron-plate had answered no other purpose, the discovery by Stevens of its capacity to resist the two most formidable weapons of his day would alone have been of great value to the country; but he went farther, and demonstrated by actual construction the idea of Montgery, that successive plates of iron would resist the cold spherical shot thrown by the best artillery, and his floating battery or frigate is protected by plate within plate of iron armor.
[Footnote A: Sheet-iron plates of one inch in thickness weigh forty pounds per superficial foot.]
While our Government slept upon its unfinished frigate, and forgot the honor and interest of the country in the lap of the siren of the South,—of that South which sixty years since broke down the navy of John Adams, and left us to encounter the embargo and war with England without a navy, or, at most, with a few frigates which sufficed to show what the navy of Adams might have effected,—the honor of launching the first iron-clad steamer, the Gloire, was resigned to the French. The first Napoleon made the army of France the best in Europe, if not in the world; the third, while he maintains the standing of the army, aspires to give the same position to her navy.
In 1854, Napoleon, who had long studied the art of war, and during his stay in New York had doubtless seen or heard of the floating battery, determined to construct two such batteries, and accordingly built the Lave and Tonnerre. With one of these, the Lave, during the Russian War, he assailed and destroyed in the brief space of one hour the strong fortress of Kinburn, near Sebastopol; and in striking contrast to this success, a large British steamship, heavily armed, but constructed of wood, was actually captured near Odessa by a small party of Russians with two or three thirty-two-pounders worked through a gap in an embankment.
The invulnerable battery of France anchored close under the fortress. Before its cannon, granite walls are shivered into fragments most dangerous to the gunners, while the shells, burying themselves two or three feet deep in the brickwork, by their explosion shake the walls to pieces. Iron, protected by iron, triumphed over both bricks and granite, which had defied the fleet of England.
The Emperor was not slow to realize the result of the problem he had solved. He at once proceeded to test the strength of the best kinds of plate made in his dominions, and found, by actual trial, that plates of the best iron, but four and three-fourths inches in thickness, were able to resist repeated shocks of solid balls fired at the distance of twenty metres (less than four rods) from his sixty-eight-pounders, and from rifled guns throwing shot of nearly the same calibre,—and this, too, when the balls were impelled by more than one-fourth their weight of powder. But ships rarely engage at such close quarters either with vessels or fortresses, and the effect of the ball is greatly diminished by distance, a single inch plate sufficing to stop a spherical shot at a long distance.
As the result of these experiments, the Emperor proceeded to construct the Gloire, an iron-clad frigate, which has been completed, has made several voyages, been tried in a severe gale, for nearly a year has been the pride of the French navy, and has recently run from Toulon to Algiers in the brief space of sixty-six hours.
The Gloire is a steam-frigate cased in five-inch plates; she is two hundred and fifty feet in length by twenty-one in width, mounts thirty-eight rifled fifty-pounders, is moved by engines of nine hundred horse-power, is manned by six hundred men, has a speed of twelve and a half knots, and a capacity for five days' coal,—a capacity which might be easily increased by a little more breadth of beam, but which is sufficient for a passage to Algiers, or along the coast of Spain, England, or Italy. This vessel is considered invulnerable by balls discharged from rifled cannon at the distance of four hundred yards.
Encouraged by his continued success, the Emperor at once ordered the construction of nine such frigates, several of which are already finished. He has since ordered ten more iron-cased frigates and gun-boats, which are now in course of construction. Before the present season closes, his iron navy will be composed of twenty steamships and four floating batteries.
During the contest with Russia, England would not venture to expose her wooden ships of the line to the close fire of the batteries either at Cronstadt or Sebastopol, and found it safer to shell them at a respectful distance and with indifferent success. She was deeply impressed, however, with the performance of the Lave and Tonnerre at Kinburn, and seriously disturbed by the completion of the great naval station at Cherbourg, armed with more than three hundred cannon, and directly opposite her coast.