marines, and every thing destructible are under cover. What is to be done when such ships, if hostile, meet? Are they to salute and retire in search of smaller fry, or are they to fight? If they fight, it would be the combat of two Achilles, without even vulnerable heels. If these ships are all that is claimed for them, there are but two ways for them to engage each other; either to sheer off, and, like two knights at tournament, charge each other, when the probability is that both would go down; or else to close and board, when victory would depend not upon the invulnerability of the ships, nor upon the caliber of their guns; and yet that is what these ships are built for. It follows that a steel-clad ship could not protect a convoy of ordinary transports against the attack of another steel-clad ship. The protector_could do nothing but witness the destruction of his convoy. It results, then, that a steel-clad ship is useful only as opposed to wooden ones or fortifications.

STEEL-CLAD SHIPS FOR THE PROTECTION OF HARbors.

It seems, then, that the peculiar province of steel-clad ships is the protection of harbors. The enemy could never make a landing in their presence, unless we suppose the whole of his forces to be embarked on similar vessels, which is impossible with the most wealthy nation, or unless we suppose the force to be a very small one. A single steel-clad ship issuing from a harbor and encountering a fleet of transports, however well protected, could destroy them. For the defence of a harbor, if a steel-clad ship encounters a similar one, the combatants who possess the shore would have an immense advantage, in the ability which they would have to put such masses of men on their ships as to overpower all resistance in an attempt to board the other. It is easily seen, then, that the protection of harbors and coasts is the true sphere for the action of steel-clad ships. We cannot be too eager to provide this protection. Government has so far had its attention entirely taken up with a pressing need for gunboats. It has done well-it has done wonders; but another need as pressing has arisen for steel-plated ships for our harbors. Let us have forts, but let us have floating steel forts, too. They are forts that do not require workmen to be sent to a certain point to erect them, but forts built wherever men and material are at hand, and to be stationed wherever needed. Such forts might sail soon enough to hold a southern harbor, when there would not have been time to gain a foothold to throw up more than a single breastwork. With such forts the harbor of Charleston can be taken, and only by such forts.

IRON PLATES FOR CASING WAR VESSELS.

A government agent lately left this country for Europe, for the purpose of obtaining some reliable data in regard to iron plates for casing war vessels. In this country, since the rebellion broke out, a number of inventions have been brought forward, both of improved armor plates, and of improved methods of securing them to the frame of the vessels. Some of them would seem to possess merit, and have been awarded patents. For instance, a patent has been secured for constructing armor plates, each having three or more ribs, which are afterwards cut by a lathe, so as

to dovetail (by means of tongues and grooves) into each other. When placed upon the vessel's frame, they are wedged together with keys, driven between them from the inside.

A patent has also been granted for a plan of rolling the plates with flanges on their inner sides, so that they may be secured in position without the necessity of punching bolt holes through the plates. Their edges are so recessed that each fits into the edge of the plate immediately below it.

Letters patent have likewise been issued for a method of constructing and arranging the plates in such manner as to obtain the benefit of their maximum strength and resistance so as to render unnecessary the expense of a heavy wooden framework. The plates proposed are of the box form, and clasp the vessel's frame.

HARBOR DEFENCES.

The introduction of iron armor for ships of war necessitates the use of far heavier artillery than has hitherto been deemed sufficient for harbor defences. None but the most powerful guns possible of construction can be expected to cripple or sink such vessels. Fortunately for us if the opinions of military authorities can be depended upon we have a monster fire-arm, capable of crushing in the sides even of a Black Warrior or La Gloire. It is the Rodman gun, which throws a ball of 420 pounds, and which General Bernard says will smash in any steel-clad ship of war. He recommends this tremendous weapon for the defence of New York. It should be furnished for all our principal seaports. He also proposes to cut down and make shot-proof the old seventy-fours, no longer of any service, and use them as floating batteries. They would be towed to and from their moorings, and would need no intricate, heavy, and expensive machinery. They would need no store of provisions; no crew but the trained artillerists needed to serve the guns; none of the ponderous lashings needed to secure heavy ordnance in sea-going ships. Heavier guns could be used on such hulks than any ship will ever dare take to sea, except as cargo. Labor-saving machinery could be applied to the handling of the heavy shot and shell, which would not work in a sea-Wolumn of water being inThe Rodman gun is cast hollow, a

troduced into the core, which forms the mould of the bore. To insure that the cooling shall be exclusively internal, the exterior of the mould is kept heated during the whole process. By this means the inventor is enabled to cast a larger effective gun than is used by any other nation. They are cast as large as fifteen inches bore, and Mr. Rodman says they may be cast of thirty inches. A fifteen-inch gun is of the enormous weight of 49,100 pounds, and the solid shot thrown by it weighs 420 pounds. A thirty-inch gun would throw a projectile weighing 3300 pounds! The shells that would probably be used with these guns would weigh respectively about 800 and 2500 pounds. General Bernard says,

When these iron-clad ships come to engage at breaching distance our earth or stone forts, we do not try to punch holes in them, we wish to stave in the whole side. For this purpose, masses of large diameter, moving with moderate velocity, are

Indispensable. The fifteen-inch shell would probably be effectual against the inclined-sided battery, and would be likely to convert Captain Cole's cupolas into shooting caps indeed. Penetrating and exploding in an iron-clad or wooden vessel, a single one would probably suffice. The inclined side of these newly-proposed ships would not, perhaps, be easily penetrated (though the side would doubtless be stove) even by such a shell. But it must be recollected that about one half of such a ship is not invulnerable

the citadel, or protected portion, occupying only the midships; and the effect of such an explosion in the bow or stern would tell fearfully upon the ship, and upon such of the crew as were not in the citadel. Fifteen inches is the caliber of the gun made as an experiment to test the practicability of casting guns of extraordinary caliber, and their efficiency. The result has convinced our ordnance officers that it is not an extreme limit. A twenty inch gun can probably be made, and not only made, but used with facility and efficiency. Enormous and expensive as they are, such guns may have their mission,' and a few of them in our important sea-coast batteries will probably be hereafter deemed an essential part of their armament."

THE MONITOR.

(See engraving, page 63.)

The iron-clad steam battery Monitor, which rendered such timely and efficient service in the naval engagement at the mouth of James River, is one of the steamers built under an act of Congress passed last summer, authorizing the Secretary of the Navy to advertise for proposals for the construction of iron-clad vessels of war, those making proposals in all cases to furnish their own plans. One of the designs accepted was from Captain Ericsson, the well-known engineer. The work on the battery assigned to him was rapidly completed, and she was launched at New York on the 30th of January last. The following description has been given of her, and we reproduce it as of interest at this time :

The vessel is described as a broad, long, flat-bottomed vessel, with vertical sides and pointed ends, requiring but a very shallow depth of water to float in, though heavily loaded with an impregnable armor upon its sides, and a bomb-proof deck, on which is placed a shot-proof revolving turret, fitted to two very heavy guns. It is so low in the water as to afford no target for an enemy, and every thing and every body is below the water line, with the exception of the persons working the guns, who are protected by the shot-proof turret. The sides of the vessel are first formed of plate iron, half an inch thick, outside of which is attached solid white oak twenty-six inches thick; outside of this again is rolled iron armor five inches thick. The bomb-proof deck is supported by heavy braced oak beams, upon which is laid planking seven inches thick, covered with rolled plate iron one inch thick.

The turret consists of a rolled plate iron skeleton, one inch thick, to which are riveted seven thicknesses, of one inch each, of rolled iron, all firmly bolted together with nuts inside, so that if a plate is started it can be at once tightened again. Upon the sides of the turret that has the port holes through which the guns are discharged, the thickness is increased by an additional

plating three inches in thickness, making the sides of the turret which will be presented to the enemy eleven inches. No cannon shot or bolt has ever yet been driven through such a mass of wrought iron. The turret is pierced in different places with four holes for the insertion of telescopes, and just outside of the holes reflectors are fixed to bend the ray of light which comes in a direction parallel with the guns through the axis of the telescope, which is crossed by a vertical thread of spider's web through the line of collimation. The sailing master takes his position in the turret, with his eye to the telescope and his hand upon the wheel that governs the motion of the small engine, and turns the turret so as to keep the guns always directed with absolute precision to the object against which the fire is directed. A scale is also arranged for adjusting the elevation of the guns with similar engineering precision, and it would seem that the firing should be directed with unprecedented accuracy. The top is covered with a bomb-proof roof perforated with holes. The lower part of the gun carriages consists of solid wrought iron beams. These are planed perfectly true, and are placed parallel in the turret-both of the guns pointing in the same direction. The ports through the side of the tunnel are only large enough to permit the muzzle of the gun to be thrust through. Inside of them are wrought iron pendulums, which close them against the enemy as soon as the gun recoils. Two of the largest Dahlgren guns are placed in this turret. The whole is made to revolve by a pair of steam engines placed beneath the deck.

To give the upper portion of the vessel the proper powers of locomotion, there is suspended beneath it another one of less strength, sufficiently narrow and sloping at the sides that if the enemy's balls should pass below the shot-proof upper vessel, these sides can only be hit at such an acute angle that no harm shall ensue, and in its length approaching the bow only so far that its raking stem may receive the shot fired from directly ahead in the same way, and at the stern giving sufficient space to permit the shot coming directly aft to pass under the shot-proof end without hitting the rudder, which is abaft the propeller. The lower vessel is of iron, one half inch thick, and made in the usual manner. It will carry the machinery, coal, &c., aft, and forward the officers' quarters, ammunition and stores. The two partitions of the vessel are separated by a wrought iron bulkhead. The machinery consists of two horizontal tubular boilers, and two horizontal condensing engines of forty inch diameter of cylinders and twenty-two inch stroke of piston.

The pilot house is only a few feet above the deck, the man standing on a platform below it. It and the turret are the only things above the surface of the deck. With all her armament, coals, and provisions on board, the Monitor draws 9 feet 9 inches, leaving 21 inches height above the water-line. On the trial trip in New York harbor, her speed, by the chip-log, was 61 knots an hour, with 65 revolutions of the engines. The boilers, being new could not be worked up to their maximum speed. The real speed of the Monitor is 7 knots, while that of the Merrimac is only 5. The Merrimac is five times as large, and carries four times the armament.

The dimensions of the upper vessel are, length, 174 feet: breadth of beam, 41 feet; depth, 5 feet; and of the lower vessel, length, 124 feet; beam at top, 34 feet; at bottom, 18 feet; depth,