Protection at, and extending several feet below the water-line, is obviously indispensable around the battery of a vessel. It is valuable at other points, but not indispensable, provided the vessel has numerous horizontal and vertical bulkheads to prevent too great a loss of buoyancy when the vessel is seriously damaged between wind and water. Harbor-craft may be very low on the water, so that only a little height of protection is required. But it is generally supposed that sea-going vessels must be high out of water. Mr. Ericsson's practice, however, is to the contrary; and it may turn out that a low vessel, over which the sea makes a clean breach, can be made sufficiently buoyant on his plan, If high sides are necessary, the plan of Mr. Lungley, of London, may be adopted,—a streak of protection at the water-line, and another forming at the top of the battery at the top of the structure, with an intermediate unprotected space. A shot-proof deck at the water-line, and the necessary shot-proof passages leading from the parts below water to the battery, would of course be necessary.
Considering the many expedients for vastly increasing the thickness of armor, the idea, somewhat widely expressed, especially in England, that, in view of the exploits of Armstrong, Clay, and Whitworth, iron-protection must be abandoned, is at least premature. The manner in which the various principles of construction have thus far been carried out will be noticed in a brief.
Description of Prominent Iron-Clad Vessels. CLASS I. Classified with reference to the protection, the dimensions of the English Warrior and Black Prince are, length 380 feet, beam 58 feet, depth 33 feet, measurement 6,038 tons. Their armor (previously described) extends from the upper deck down to 5 feet below water, throughout 200 feet of the length amidships. Vertical shot-proof bulkheads joining the side armor form a box or casemate in the middle of the vessel, in which the 26 casemate-guns, mostly 68-pounder smooth-bores, are situated and fired through port-holes in the ordinary manner. Their speed on trial is about 14 knots,—at sea, about 12. The Defence and Resistance, of 275 feet length and 3,668 tons, and carrying 14 casemate-guns, are similarly constructed, though their speed is slow. All these vessels are built entirely of iron.
CLASS II. This differs from the first mentioned in having protection all around at the water-line. The New Ironsides, (American,) of 3,250 tons, 240 feet length, 58-1/2 feet beam, 28-1/2 feet depth, and 15 feet draught, and built of wood, has 4-1/2-inch solid armor with 2 feet backing, extending from the upper deck down to 4 feet below water, with vertical bulkheads like the Warrior, making a casemate 170 feet long, in which there are sixteen 11-inch smooth-bores and two 200-pounder Parrott rifles. A streak of armor, 4 feet below water and 3 feet above, runs from this forward and aft entirely around the vessel. Her speed is 8 knots. The Stevens Battery, (American,) 6,000 tons, constructed of iron and nearly completed, is 420 feet long, 53 feet wide, and 28 feet deep from the top of the casemate, and is iron-clad from end to end along the water-line. As proposed to the last Congress, the central casemate was to be about 120 feet long on the top, its sides being inclined 27-1/2 degrees from the horizon, and composed of 6-3/4 inches of iron, 14 inches of locust backing, and a half-inch iron lining. Upon the top of it, and to be loaded and manoeuvred from within it, were to be five 15-inch smooth-bores and two 10-inch rifled guns clad with armor. The actual horse-power of this ship being above 8,000, her speed would be much higher than that of any other war-vessel. Congress, declining to make an appropriation to complete this vessel, made it over to Mr. Stevens, who had already borne a considerable portion of its cost, and who intends to finish it at his own expense, and is now experimenting to still further perfect his designs. The Achilles (English) now building of iron, about the size of the Warrior, and of 6,039 tons, with a casemate 200 feet long holding 26 guns, belongs to this class. The Enterprise, 180 feet length, 990 tons, 4 casemate-guns, and the Favorite, 220 feet length, 2,168 tons, 8 casemate-guns, are building in England on the same plan. The Solferino and Magenta, (French,) built of wood, and a little longer than the Royal Oak, (see Class III.,) are iron-clad all round up to the main deck, and have two 13-gun casemates above it.
CLASS III. The Minotaur, Agincourt, and Northumberland, 6,621 tons, and 390 feet length, resembling, but somewhat larger than the Warrior, in all their proportions, and now on the stocks in England; are built of iron, and are to have 5-1/2-inch armor and 9-inch backing extending through their whole length from the upper deck to 5 feet below water, forming a casemate from stem to stern, to hold 40 broadside-guns. Five vessels of the Royal-Oak class, 4,055 tons, building in England, 277 feet long and 58-1/2 feet wide, are of wood, being partially constructed frigates adapted to the new service, and are iron-clad throughout their length and height to 5 feet below water. They are to carry thirty-two 68-pounders. The Hector and Valiant, 4,063 tons, and 275 feet long, are English iron vessels not yet finished. They are completely protected, and carry 30 casemate-guns. All the above vessels are to carry two or more Armstrong swivel-guns fore and aft. Four vessels of La Gloire class, (French,) 255 feet long and built of wood, resembling the Royal Oak, carry 34 guns, and are completely clad in 4-1/2-inch solid armor. Ten French vessels, of a little larger dimensions, are similarly constructed. The Galena (American) is of this class as to extent of protection. The quality of her armor has been referred to.
CLASS IV. Ships with Revolving Turrets. The Roanoke, (American,) a razeed wooden frigate of 4,500 tons, is 265 feet long, 521/2 feet wide, and 32 feet deep, and will draw about 21 feet, and have a speed of 8 to 9 knots. This and all the vessels to be referred to in this class are iron-clad from end to end, and from the upper deck to 4 or 5 feet below the water-line. The Roanoke's plates (solid) are 4-1/2 inches thick, except at the ends, where they are 3-1/2, and are backed with 30 inches of oak. She has three turrets upon her main-deck, each 21 feet in diameter inside, 9 feet high, and composed of 11 thicknesses of 1-inch plates. Her armament is six 15-inch guns, two in each turret. Of the Monitors, which are all constructed of iron, two now building are to be seagoing and very fast, and are to act as rams, like several of the other vessels described. One of these, the Puritan, is 340 feet long, 52 feet wide, and 22 feet deep, and will draw 20 feet. The armor of her hull, 10-1/2 inches thick, composed mostly of 1-inch plates and 3 feet of oak backing, projects beyond her sides by the amount of its thickness, and overhangs, forming a solid ram 16 feet long at the bow. The whole upper structure also overhangs the stern, and protects the screw and rudder. This vessel will carry two turrets, 28 feet in diameter inside, 9 feet high, and 2 feet thick, composed of 1-inch plates. Each turret contains two 15-inch guns. The other vessel, the Dictator, is similarly constructed, except that it has one turret, two guns, and 320 feet length. The upper (shot-proof) deck of these vessels is 2 feet out of water. The 18 smaller Ericsson vessels, several of which are ready for service, are 18 inches out of water, of light draught, and about 200 by 45 feet. Their side-armor, laminated, is 5 inches thick, upon 3 feet of oak. They have one turret, like those of the Roanoke, and carry one 15-inch gun and one 11-inch smooth-bore, or a 200-pounder rifle. The original Monitor is 174 by 44-1/2 feet, with 5-inch side-armor, and a turret 8 inches thick, 20 feet in diameter inside, and armed with two 11-inch guns. These vessels of Ericsson's design are each in fact two vessels: a lower iron hull containing boilers and machinery, and an upper scow overhanging the ends and sides, forming the platform for the turret, and carrying the armor. The Onondaga, now constructing, is an iron vessel of 222 feet length, 48 feet beam, and 13 feet depth, with 4-1/2-inch solid armor having no backing, and without the overhanging top-works of the Monitors. She has two turrets, like those of the Roanoke, and four 15-inch guns. Nearly all the vessels of Class IV. are without spars, and have a pilothouse about 6 feet in diameter and 6 feet high on the top of one of the turrets.
The English Royal Sovereign, 3,765 tons and 330 feet length, and the Prince Albert, 2,529 tons and the same length, are razeed wooden vessels. The former carries 5, and the latter 6 of Captain Coles's turrets with inclined sides, each turret designed for two 110-pounder breech-loading Armstrong guns. The class of iron vessels constructing to carry two of Coles's turrets are 175 feet long, having 42 feet beam, 24 feet depth, 17 feet draught, and 990 tons displacement. All these English vessels are much higher out of water than Ericsson's.
Besides these classes, there is the variety of iron-clad vessels called turtles, from their shape,—among them, the Keokuk (Whitney Battery) 159-1/2 feet long, with two stationary 11-inch gun turrets,—and a class of Western river vessels of very light draught and some peculiarities of construction. The latter resemble the Stevens Battery in the shape and position of their armor, but carry their guns within their casemates.
The Stevens Battery, the Onondaga, and the Keokuk have independent screw-propellers, which will enable them to turn on their own centres and to manoeuvre much more rapidly and effectively in action than vessels which, having but one propeller, cannot change their direction without changing their position, and are obliged to make a long circuit to change it at all. This subject is beginning to receive in Europe the attention which it merits.