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Iron-Clad Vessels.
On the 16th of September, 1861, the Commmittee of Naval Constructors appointed to examine the various plans presented for the building of iron-clad vessels made their report to the Secretary of the Navy. Plans and specifications were submitted to them for vessels ranging from 83 to 400 feet in length, to cost from $32,000 to $1,500,000. Of these they recommended three for adoption: the Galena; the Ironsides, now building at Philadelphia; and Mr. Ericsson'sMonitor. Their approval of the Monitor was cautiously worded. They say:
"This is novel, but seems to be based upon a plan which will render the battery shot and shell proof. We are somewhat apprehensive that her properties for sea are not such as a sea-going vessel should possess. But she may be moved from place to place on our coast in smooth water. We recommend that an experiment be made with one battery of this description on the terms proposed, with a guaranty and forfeiture in case of a failure in any of the points and properties of the vessel as proposed."
This Committee could not have anticipated
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that their report was the most important military event of the century; that in its results it was to annihilate not only the "wooden walls" of England, and to put an end to the building of British Warriors and French Gloires, but also to introduce an entirely new element into coast defenses not less important than the costly and elaborate fortifications with which all maritime nations have heretofore protected their harbors and great depots. Novel as the plan was of necessity to the Committee, it was no sudden conception of the inventor. It had been thought out to the minutest detail, and existed in the teeming brain of Mr. Ericsson, and had been constructed in drawings and models by his busy hand, years before the first actual blow had been struck upon her iron sides.Of the Monitor herself and her achievements we do not now propose to speak at length. Every body knows the appearance of the low black raft, rising scarcely 18 inches above the water, with its harmless-looking "cheese" in the centre of its smooth deck. Certainly to the eye of the nautical critic she is not a beautiful vessel; but her inventor knew too well the work which she was to do to sacrifice invulnerability to wave lines. Speed even, though a very desirable thing, was secondary. He was to build a floating battery, not a clipper which could cross the Atlantic in nine days, or round Cape Horn to San Francisco in three months. The object which he proposed was immediate and pressing, and the result crowned the work.
It was fortunate for him, but still more so for the country, that the practical carrying out in iron of his plan fell into capable hands. The contract for building the hull was undertaken by Mr. J. F. Rowland of the "Continental Works," and the work was pushed forward with such rapidity that in just ninety days after the contract was signed the Monitor, with her engines on board, and in actual working order, was launched. Mr. Rowland modestly disclaims any credit beyond that of faithfully and successfully carrying out the ideas of the inventor. "Mr. Ericsson," said he, "was in every part of the vessel, apparently at the same moment, skipping over planks and gangways, and up and down ladders, as though he were a boy of sixteen. It seemed as though a plate could not be placed or a bolt struck without his making his appearance at the workmen's side." We think the proprietor of the "Continental Works" was over-modest. The administrative skill and energy which could set hundreds of men at work upon tasks new to them — could devise means and implements, almost upon the spur of the moment, by which ideas which only existed in lines upon paper and wood were wrought into solid iron — is of no common order. And we are glad to see that the construction of at least four of the new Monitors, which our Government ordered immediately after the triumphant success of the first, has been placed in the hands which so successfully executed the original. One thing, which was mentioned to us almost incidentally, shows the prompt adaptation of means to ends. The Monitor, while on her "ways," was quite generally regarded as an experiment that would be sure to fail. She was deficient, it was said, in this point and that. She could not carry her weight of armor; her turret would not revolve properly; no living men could work her guns in that narrow space; and, first of all, in the judgment of experienced ship-builders, she could never be launched. If any one will look upon the illustration which heads this paper, he will see that there was plausibility in this opinion. The raft-like upper hull, projecting far beyond the lower one, was so loaded with armor as to be far heavier than water, and besides there was the weight of the ponderous turret and the heavy machinery. This would strike the water first, with nothing to sustain it, and so when the vessel slid from her inclined ways, she would go straight down to the bottom like an iron bar. "If Ericsson ever finds his battery after she is launched," it was said, "he will have to fish her up from the mud into which her stern will surely plunge." And so he would have done had she been sent alone from her "ways." But this casualty had been foreseen and provided for by Mr. Rowland. Two great wooden tanks had been prepared, which, before the launch, were chained to the almost solid overhanging stern of the upper hull, buoying it up as they touched the water until the lower hull came into the stream. Valves in the tanks were then opened the water rushed in, sinking them down; then they were disengaged, floated off, and in a quarter of an hour the Monitor rested upon an even keel. As we have said, she was launched, contrary to the usual custom, with her engines on board. These had been put in working order beforehand; and as far as the builders were concerned, the battery might have put to sea in half an hour after her launch.
We shall revert to the general construction of the vessels of which the Monitor is the type in the course of this paper, when we describe our visit to the "Continental Works," to note the process of building the new vessels of her class. In the mean while we propose to describe the processes of the manufacture and adaptation of the solid iron plates which, where applied to ordinary wooden vessels, convert them into what our French neighbors call Vaisseaux en cuirass — or, as we say, "iron-clad vessels." In our Magazine for April of this year we described the "Building of a Ship" of wood. Such a vessel was the Merrimac, now no more. Such is the Roanoke, built upon the same lines, which is now at the Brooklyn Navy-yard, undergoing the process of being converted into a mail-clad vessel, by covering her wooden sides with solid plates of iron. These plates are in all essential respects the same which are made for the Ironsides, now building at Philadelphia. The manufacture and fitting of these plates for the Roanoke are performed at two establishments in New York, the "Franklin Forge" of Tugnot, Dally, and Co., and the "Novelty Works," of
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which we gave a full description in this Magazine for May, 1851. In both the courtesy of the proprietors gave us every facility for observation, with the privilege of making drawings of every thing which would aid in the elucidation of the subject. We were also accompanied by a friend,There are two methods of producing plates of iron. By one they are "rolled;" by the other "hammered." Long discussions have been held in scientific circles as to the relative advantages of the two methods. We have not space to enter into these; but the general result of all seems to be that, for armor composed of successive layers of comparatively thin plates, rolled iron — on account of the greater speed of its manufacture — is the best upon the whole; while for solid plates that which is hammered is preferable — the close interlacing of the fibres of the metal under the hammer more than compensating for the increased labor. The plates whose manufacture we are about to describe are hammered.
To see the production of these we go first to the "Franklin Forge," on the First Avenue, near Twenty-fifth Street. The main business of this establishment is the execution of large forgings. Here was forged the shaft of the
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Adriatic, larger than any one upon the Great Eastern. As we enter every thing shows the ponderous character of the work done here. Huge engines, steam-moved, are shaping, carving, and boring enormous masses of iron. At the outset we notice the great hammers which perform the forging. They differ in every respect from those used ten years ago, when the "Atlantic Forge" of the Novelty Works, a representation of which we reproduce, was capable of doing the heaviest work required. In an out-of-the-way corner of the "Franklin" we saw a forge of this kind laid aside as useless. The forges now used for heavy work are the "Steam Hammers," which appear in the subsequent illustrations. The hammer is raised like the piston of a steam-engine, and falls by its own weight. The largest of these forges faces the entrance, and is represented in the illustration "Forging a Plate." It looks at first view much like the gateway of a Gothic church. The hammer, which we shall soon see in operation, weighs seven and a half tons. We wish to commence at the beginning, and so, leaving for a time the forges, we pass on to the rear, where is heaped up the raw material which is to be wrought into plates. This is "scrap iron" — iron of every form and use, which, having performed its functions in one shape, has been brought here from a thousand quarters to undergo a new transmutation. In the economy of manufactures, as in that of nature, nothing is absolutely lost. In one heap we see piled up fragments of steam-engines, reaping machines, and the like; close by is a pile of the worn-out fragments of smaller wares. We took the trouble to note some of the articles in this pile of old iron. There were locks and padlocks, rusty keys, kitchen pokers, knife-blades, screws, steelyard beams, skate irons, curling-tongs, halves of shears, sofa springs, cork-screws, shovel-blades, tong-handles, pot-hooks, spoons, ladles, bridle-bits, and above all horse-shoes. Not a bit or fragment of iron is lost. Every ounce has its value, transmutable, if not into gold, into copper and silver when brought to any foundry. The larger pieces have to be cut up437
in order to get them into manageable size. This is done by the "Cutting Machine" — an instrument not unlike, in general appearance, the "straw-cutters" used by farmers, in which the knife descends perpendicularly. The thickest boiler-plates are shred by it as easily as a child cuts a sheet of paper with her scissors; bars as large as a man's ankle are cut apart with no more apparent effort than is required to slice a radish.These scraps are piled up into "fagots" about two feet square, and thrust into the furnaces of which we see a row, looking not unlike bakers ovens, and in fact scarcely larger. The draft of these is supplied by a fan, which revolves 1800 times in a minute, creating the most intense heat; tongues of white flame shoot out from every crack and crevice. In about an hour the loose fagot is brought to a welding heat. One workman raises the furnace-door, while another grasps the ductile fagot with a long pair of tongs, and by means of a chain suspended from a movable pulley, wheels it around and places it on the anvil of the forge. It is of an intense cherry-red, so bright that the eye can hardly look upon it, and apparently as ductile as wax. The end of a long iron rod, with a crank-like bend in the handle, is laid on the fagot. Down comes the ponderous hammer; the first blow shrinks the glowing mass to half its former dimensions, and welds it firmly to the handle, by which the stalwart workman turns it over and over. The blows fall thick and fast, and in two minutes the fagot is reduced to a solid mass, looking like a rough fragment of joist, some four feet long and six inches square. This is called a "bloom," and is a homogeneous mass of iron; the locks, bolts, boiler-plates, pokers, screws, and horseshoes of which it was composed having lost their personal identity. A long-handled knife is then applied; one blow of the hammer upon this severs the rod from the bloom. This is grasped, still red-hot, by another workman with a pair of tongs, placed upon a truck, and wheeled away to cool.
These blooms are to be welded and hammered into plates. As we passed the great seven-and-a-half-ton forge at the entrance, we saw behind it a row of oven-like furnaces, into the mouth of each of which was thrust a round beam of iron, some 15 feet long and as large as a man's body, suspended by a chain and pulley from the arm of a huge crane. This bar is simply the handle for managing the plate during the process of forging it from the blooms. The process is this:
The end of the bar is flattened out, something like a shovel; upon this a pile of the blooms is placed, in four or more layers, crossing each other, as one "cords up" the end of a pile of wood. This is thrust into the furnace, and under the intense heat in two or three hours the mass becomes ductile. While watching the forging of the blooms we are told that they are about to begin forging a plate. We hurry back to the place, and hear a signal given. A score of stout men, whom we have seen apparently resting about, rush forward: one with a long bar pulls
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away the loose fire-brick which close the mouth of the furnace; another climbs the stairs, a tall story high, to the top of the forge, and lays hold of a lever which governs its action; a half dozen more manage the crane; while the remainder lay hold of the handles which are clamped about the solid round bar. The crane swings round; the bar is withdrawn from the furnace and wheeled under the hammer. This comes down with a heavy thud from its full height, with its 15,000 and more pounds weight. These blows are too much for even the stubborn blooms; they seem to glow with impotent rage, and send out fiery sparks as the huge weight falls upon them and subdues them to its will. It is wonderful to see the facility with which the dozen stout, swarthy Titans manage the huge bar of iron, which is delicately balanced upon its suspending chain. They tug at the handles until every muscle of their arms and chests stand out like whip-cords; they turn it over and over, presenting now this side, now that; now one edge, and then the other to the blows of the hammer. In a few moments the piled-up blooms are blooms no more, and have been converted into a portion of a plate. This process is repeated, fresh piles of blooms being heaped up upon the end of the plate, heated and hammered out, until the required length has been attained.The plate thus built up is still rough and covered with scales. It has to be smoothed off. This is done by the same forge which shaped it. It is again heated and water thrown upon it as it comes under the hammer. This does not, as one would suppose, flash up at once into steam, but rolls in globules. The hammer falls upon these, they explode with a noise like the firing of a platoon of musketry, carrying off all the scales, and leaving the plate as smooth as a newly-planed board.
The dexterity with which this heavy hammer is managed by the workman on his high platform is something wonderful. He can give at will a blow of the full force of the ten-feet fall of the seven-and-a-half-tons hammer, aided by the expansive force of the steam let in above the piston, or a stroke as light as the tap of a lady's fan. " We can chip an egg by this hammer without crushing it," said Mr. Tugnot to us. We did not see the experiment tried; but as we watched the blows, now heavy, now light, as the sides or edges of the plate were presented, we had no doubt that the statement was literally true. We may say, in passing, that a couple of years ago one of the proprietors of the " Franklin Forge," while in Great Britain, visited the leading mechanical establishments, and found nothing equal to his own. "I would not give shop-room to their machines!" he said.
There is no limit to the size of the plates which may be made by the processes which we have described except that imposed by the facility of handling. As they leave the forge the usual size of our Roanoke plates is about three feet wide, twelve or fifteen long, and four and a half inches thick. The thickness of the plates, as it happens, is just that of the width of a page of this Magazine. Such a plate weighs from 4000 to 7000 pounds, according to its size. As it leaves the forge it is a solid plank of iron,
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attached to the heavy "handle" of which we have spoken. It is cut off from this by a machine, which squares both ends. The plates of irregular shapes, which are required for special parts, are fashioned by appropriate machines. Beyond this, the whole of our Roanoke plates are wrought by the hammer. They are simply planks of iron, and with the production of these the work of the Franklin Forge ceases. Now as no part of the sides of a ship is a plane surface, these plates must all be bent to special curves, and the holes drilled in them for the bolts which are to faster, them to the sides of the ship. This work is performed at the "Novelty Works," to which we will follow our plates.Pending the arrival of our plates we will explain what is to be done. The holes for the bolts have already been bored in the ship's side by the carpenters, and the lines have been drawn upon her by which the size and shape of our plates has been determined. Now in order to have the holes in our plates come exactly over those bored in the wooden body we must have a facsimile, or "templet," as it is called in carpenter's work, of every part of the hull. This is easily done by taking a piece of thin board and marking the holes in it through the vessel's side. The whole series of templets will cover the whole of the ship's sides which are to be covered with plates. Now lay "templet No. 1, bottom course," upon "plate No. 1, bottom course," marking upon it the precise place for the bolt holes, and we are ready to go on with our work of drilling. There must be the utmost precision in this. Suppose, for example, that our templet is not marked quite right, that instead of the holes coming, as they should, exactly over the ones in the frigate, one or two of them come half-way over the hole or to one side of it, it will be a difficult thing to remedy. One of two things must be done: either the wood must be cut away to suit the plate, or else the plate must be made to suit the ship, otherwise the bolt could not pass through. As our armor is four and a half inches thick, you will see that it is not a desirable task to cut through so far in so small a hole; on the other hand, the bolts must fit water-tight in the ship, and if the carpenter plugs the hole and makes a new one, we may spring a leak in action and so lose the vessel. Having seen the necessity of caution we will mark off our plate, which has now arrived at the shop.
Let us then chalk our piece of armor all around the place where the holes are to be drilled, lay the facsimile of the ship's side upon it, and mark through with a steel point; now remove the templet, and you will see a number of little circles which you are to follow in drilling. Now call some of those strong-armed laborers, and they with the aid of the crane will transport the mail to the shop where it is to be drilled. Here they will place it on a long bed, which is provided with rollers so that it can move easily. The drill is set revolving, and in a short time the hole is bored through the plate. This hole must also be "countersunk." As you may not know what that is, I will tell you that it is a depression in the shape of an inverted cone, so that the head of a common wood-screw would fit in it, except in ours it is many times larger. You will look at the top end of the drill now, and where it enters into the machine will see that there is a V-shaped part. This is the countersink; it being flat and having sharp edges, revolves in the hole which the drill has made first, and so leaves its own impression there. It is not customary to have the drills made in this manner; but we have many holes to drill, and can not wait to change it for another. We have counter-sunk our plate, so that the bolts which go in the holes may sink in even with the outer surface.
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If they were square on the head outside, when shot struck them they would be broken off and the plate would become loose. Now, if an enemy will only hit one of these countersunk bolts, we should be very much obliged to him, as we could then screw up the nut on the other end of the bolt, and so make the armor more secure. The drill is "fed" through the plate by means of a screw, and you will see the iron starting out from it in a thin spiral. It is supplied with soft soap and water, not because it is dirty, but to keep it cool: were it not for this it would speedily become hot with friction, lose its temper, and do nothing. We have now got our first plate drilled and countersunk according to our templet. The plate must now be made to conform to the ship's side. It is merely a straight flat piece; but the vessel has a beautiful curve throughout its length except in the middle, where the curvature is slight, and to this the solid plates must be made to fit as closely as a glove does to the hand.
As it happens they are not quite ready to show us the operation of bending these solid plates, but in the mean while we are asked to see the mode of building a "turret," like that of the Monitor; for our ship, the Roanoke, is to have three of these turrets. These are made of a series of plates of rolled iron, eleven in number, each an inch thick. As they come here from the mills where they are rolled they are simply iron boards, nine feet long, three wide, and an inch thick. Each of them is to be bent into the shape of the segment of a circle, twenty-three feet in diameter, which is to be the size of the turrets. For this purpose a massive press has been prepared. The bed, which is movable up and down, has its upper surface turned to the precise curve of the turret. This is raised by a hydraulic ram capable of giving a pressure of 1400 tons against a stationary plate, whose lower surface has the same curve as the bed. The flat turret plate is slid into this press, the ram is worked, the bed rises, and the plate is bent to the curve of the mould. This is done without heating the plates, the enormous pressure being sufficient to give them the form required, without the necessity of rendering these inch plates ductile by heat. They are now taken to an adjacent building and temporarily set up into a turret. Here a circle of solid oak timber has been laid down as a foundation. Upon this a frame-work of boards lias been built of the shape of the turret, to support the plates in the position which they are to assume. This looks much like the skeleton of a gigantic cistern. Against this frame the plates of the first course are placed, the necessary holes for the bolts having been meanwhile punched in them. Then the second course is set up against this, the bolt holes of which must be made to correspond exactly with those of the first. This is done by a simple process. The end of a pine stick, of the size of the holes in the first plate, is covered with paint, thrust through the holes, leaving its mark on the plate of the second course. These white marks show exactly where the holes in the second course are to be made. This being done, the third course is set up in like manner; the places for the holes marked, the plates taken away and punched, brought back again, set up in place; and so on with the whole eleven courses of which the turret is composed. The holes in these plates are punched instead of being drilled, as we have seen done in the thick plates. This is performed by a powerful punching machine, which, at a single stroke, drives out a "button," making a clean hole of the size required as rapidly as the workmen can move the plates under the punch. We have seen twenty holes of this size punched in a minute. The courses are all so arranged as to "break joints;" that is, the joints between no two courses are directly opposite each other. The courses being all set up, if we look through the holes we shall see that, although they come very well in a line, there are some little irregularities — a very slight variation in each plate becoming quite noticeable when multiplied by the whole eleven. This is very easily remedied by means of a steel instrument called a "reamer" — a bit, in fact, with two sharp edges. This is passed through the whole length of the hole, and turned about trimming off all the irregularities, and making the hole as smooth as the bore of a gun. Our turret is now see up and finished, will the exception of the fixtures and the portholes for the two guns. These are to be drilled out of the solid mass, and the edges of the plates properly secured. Each plate has
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of course been numbered — "Plate 1, Course 1," and so on through the whole series, 242 for each turret, if we count correctly so that, having been taken down, they can be readily set up on board the vessel itself in just the same order. On the vessel the turret rests upon a circular base of brass, which revolves upon a similar plate apon the deck, by means of a shaft worked by a steam-engine.We are now told that the operation of bending the Roanoke plates is to begin. We cross to another shed, where we see a furnace about the size of a carpenter's work-bench, with a movable iron cover. In this lies the plate, resting upon its fiery bed; for these plates must be softened by heat, since we have not yet attained to machinery powerful enough to bend such a solid mass of iron when cold. A few yards distant is the press, which differs wholly from that which we saw bending the turret-plates. As no half-dozen of the ship-plates have precisely the same curve, it is necessary to have a pair of dies for each shape. To make so many separate dies would ba a work of enormous labor and cost.
The necessity of this is obviated by a very simple contrivance. The bed, or lower die, consists of a series of large iron bars running across the width of the press. Each of these rests upon a stout screw at each end, by which it can be raised or lowered at will. A templet representing a model of a particular part of the ship's side is laid upon these bars, which are raised or lowered, at one end or both, until they exactly fit the model. The upper die, which is movable, is a heavy iron casting, with adjustable bars on its lower surface, like those on the top of the lower
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die; this is let down, and the bars are adjusted to those of its mate, and then we have a mould for this particular plate. In this way any required curve can be given with a single pair of dies by adjusting the bars in the proper position. The plate, which has been for two hours in the furnace, has become thoroughly heated to a cherry red, in which state it is apparently almost as ductile as lead, and is ready for bending. A sort of three-fingered iron hand has been resting under it. A crane mounted on a truck moving upon rails is wheeled up, the chain attached to the hand, the plate withdrawn from the furnace, wheeled to the press, and swung between the dies. The upper one, which has been raised a yard or so, is let go, and comes down with a rush, and the softened plate is bent nearly to the form of the dies at once. There are also a set of screws along the sides for tightening the dies where necessary. The foreman glances along the plate, and if any part has not come down the screws at the place are tightened by means of a wrench turned by two stalwart men; the perspiration, forced out by the heat from the glowing plate and their own exertions, streams from every pore; but slowly and surely the screws are tightened, and the plate is brought exactly to the required sweep. The whole operation of bending, after the plate has once been put in the press, hardly occupies five minutes. It is then swung out by the crane, and deposited upon a truck to be wheeled away and suffered to cool. Our plate is now finished, and will fit to its required place on the ship's side as closely as a coat made by the most accomplished master of the sartorial art.We will now follow our plate to the Navy-yard, in Brooklyn, where it is to be fitted to our ship, the Roanoke, which lies in the dry dock, waiting for us. On the way, however, we stop at the "Continental Works," to observe the process of building the new Monitors, for so we must designate them until they have received their appropriate names. There are three of them in different stages of construction; so that we tan take in at a glance the different processes of constructing the hulls of an iron vessel.
In our Magazine for April of the present year we described minutely the processes of building a wooden ship. All the preliminaries are the same for an iron vessel. The model, plans, and working drawings are made in precisely the same manner. But they are to be wrought out in iron instead of wood, which requires a great deviation in details. In place of large oaken "knees" and "futtocks," we have slender-looking "ribs" of iron; instead of thick planks for the "skin," we have iron plates of less than an inch in thickness. If we conceive an Indian canoe enlarged to the size of a man-of-war, we shall have an almost perfectly accurate idea of the hull of an iron vessel, as we see it in process of construction, bearing in mind only that the birch-bark sides and slender ashen supports are replaced by iron plates and ribs. These plates and ribs are riveted together in the most elaborate manner, and this constitutes the chief apparent work of building an iron hull. Plates and ribs have been bent each to its exact shape, and the countless holes have been punched, every one being to a hair's-breadth in its appropriate place, before the pieces are brought to the stocks where they are to be built up. Upon each vessel are a hundred or two of workmen, seeming to cling like bees to its sides. Little portable furnaces at short intervals are heating the rivets, which boys are carrying around to the places where they are wanted. The riveter takes one of these, red-hot, and thrusts it through the hole; another workman, on the other side, holds a heavy iron bar against the end; the first workman, or, more likely, two of them — for the work must be done while the rivet is hot — hammers it home. A head is thus formed upon each side, and the rivet contracting in cooling binds the plates together, making a water-tight and air-tight joint. They have to work in almost every conceivable position; hammering upward, downward, and sideways. Sometimes we see them flat upon their backs, like miners in narrow
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scams of coal veins, striking upward. So plate by plate the hull is built up, from keel to deck. As we look upon her the first impression is one of extreme fragility. If we cut an egg-shell lengthwise through the centre, one half of it would present an appearance not unlike, in shape and the comparative thickness of structure, our iron hull, which is to float the defensive armor and aggressive turret of our new Monitor. In fact if it were to be exposed to a cannon-ball, it would be pierced as easily as an egg-shell would be by a pistol-bullet. But it is to be exposed to no such hazard. It is to be protected by a shield which, in a general way, we may consider impregnable.Whether any thickness of armor can be absolutely impregnable may be a matter of doubt. There is an old paradox of the schoolmen which runs in this form: "We can conceive of an irresistible force and also of an immovable body. Now suppose this irresistible force meets that immovable body what will be the result?" The answer is, that the irresistible force will be resisted, and the immovable body will be moved. A question not unlike this is presented to artillerists and naval constructors of our day: "Can a gun be constructed which will send a ball through any armor that can be made and can an armor be constructed which will resist a ball from any possible gun?" Theoretically, we must answer both of these questions in the affirmative, and so give the paradox: "We can make armor which will resist any shot, and can make guns that will penetrate any armor." Practically — the vaunted English experiments of Sir William Armstrong to the contrary notwithstanding — we think the advantage lies on the side of the armor. We believe that our new Monitors will be, for all practical purposes, impregnable. We think the chances are a hundred to one that the turrets which we have described would not be injured by any gun yet constructed; and that if additional strength should be required to repel an additional projectile force, that the thickness of armor can be increased more easily than the projectile force. Theoretically, there is no limit to either. Practically, there is a limit to both; and this, we think, will be reached in the case of the cannon sooner than in that of the armor.
Let us now look at the means which were taken to render the hulls of our new Monitors impregnable. The thin shells which we have seen building are to be placed beyond the reach of the shot of the enemy, which would pierce them as if they were parchment. About five feet from the top of our hull an iron shelf, strongly braced, projects about four feet from the side. The width of this shelf is filled up first to the thickness of more than three feet with blocks of solid oak, all around the vessel. Outside of this solid mass of wood, braced with iron, are bolted the armor plates. It is yet a moot question whether a given thickness of iron possesses more resisting power if composed of one solid plate or of a series of thinner plates. Our Roanoke armor, as we have seen, is of solid plates; that of the new Monitors is to be of a series of five plates, one over another, each an inch thick, or five inches in all. This armor-shelf, as we have seen, projects about four feet over the sides of the thin hull, which we have described. It is some five feet high. This hull and all but two feet of the armor-shelf is below the water when the vessel is afloat; consequently, no shot fired from an opposing vessel or battery can possibly reach the lower hull without first having penetrated the iron-plated armor timbers. This "platform" — for this is the most convenient term by which to designate it — projects at the sides, as we have seen, about four feet beyond the proper hull; but at the bow and stern much more, in order to afford a like protection to the rudder, propeller, anchor, and capstan. The projection at the stern is about ten feet, at the bow about sixteen. In the illustration which heads this article, the original Monitor, as she appeared out of water, is accurately given from a drawing "made to scale" at the "Continental Works." In the new Monitors — for so we must provisionally call them — some modifications in lines and proportions have been introduced, which we do not think proper to specify. They only affect points of detail. The first Monitor was so thoroughly "thought out" by Mr. Ericsson that in all essential features the others are copies of her upon a larger scale, with increased powers of offense and defense — thicker armor, sharper lines, stronger turrets, and heavier armament.
We note in leaving the "Continental" that they are "putting up" the turrets. The process is the same as that which we saw at the "Novelty," with the exception that the plates are bent heated instead of cold; and so the powerful hydraulic press is dispensed with. A plate, after being brought to a red heat, is brought to a mould of the required curvature. One edge is fixed under a stationary clamp; a movable clamp is screwed down upon the other edge, and thus the plate is bent to the shape of the mould, the operation being aided by hammering down the plates with heavy wooden beetles. The result is the same in both cases: the plates take the required form. Which mode is better is purely a question of economy and time. In the one case the work is done by costly machinery, without heating and by few men; in the other, by simple and inexpensive machinery, but with a larger force of workmen.
The description of the armament of these vessels — that is, of their offensive power — does not come properly within the scope of this paper. We merely say in passing that the revolving turret of Mr. Ericsson — one of the two most striking features of the Monitor —; is designed simply as a means of always keeping an enemy before her guns; as they command the whole range of the horizon, no manoeuvring can elude them. They can be pointed in an instant in any direction. The two guns are thus rendered equal in effective force to at least eight mounted on stationary carriages.
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We now pass on to the Navy-yard, where our Roanoke is awaiting the arrival of the plate whose manufacture we have so patiently watched. She was once a double-decked frigate, the companion and counterpart of the ill-omened Merrimac; but has now been cut down, so that when afloat she will present a comparatively small surface to the fire of an enemy. The accompanying diagram will illustrate what we mean by "cutting down" a vessel. We do not think it advisable to give the exact lines of the Roanoke. Our diagram represents the hull of the English Royal Sovereign, 131 guns, as she was, and as she is to be when cut down to a " cupola battery" with five turrets. The light lines give her original appearance with her five rows of port-holes; the dark lines show her shape as cut down. A change something like this, only not so great, has been made in the appearance of our Roanoke. We may here note that Captain Coles of the English navy claims to be the inventor of the "cupolas" or " turrets," as applied to the protection of guns. His cupolas differ in form and construction from those of Mr. Ericsson, but the idea is the same. It is abundantly capable of proof that Mr. Ericsson proposed this mode long before Captain Coles broached it to the British Government; and while we are not justified in affirming that the Englishman borrowed it from the American, it is certain that the reverse was not the case. Not improbably the idea may have occurred to each, quite independently of the other. It is certain, however, that Captain Coles's project met with no favor from his own Government until the success of the Monitor had demonstrated the value of the idea.
We now come to our Roanoke. She lies in the Dry-Dock, held up by blocks and shores, and surrounded by scaffoldings, upon which a small army of men are busily engaged. The plate is lowered to the scaffold by guys and blocks, after which it must be managed by handspikes, levers, and movable "rams"; for the sides and ends of the ship below the water-line retire so rapidly that we can not get at them with cranes and pulleys. After infinite tugging the plate is lifted to its place. We find it fits exactly, and the holes in it come directly over those in the ship's side. The bolts are driven in; their heads fit tight into the "countersink," leaving a smooth surface outside; the nut is put on on the inside, and screwed up by a heavy wrench. So plate by plate, and course by course, the ship's sides, from some distance below the water-line, are armed in mail.
The bow is also to be furnished with a "ram". To construct this the forward plates, instead of terminating at the stem of the vessel, are allowed to project some feet beyond. At the extremity a solid piece of iron is placed between the plates projecting from the two sides, and the angular space between this and the proper bow of the ship is filled up with solid timber, all firmly bolted together. The accompanying diagram shows the form of the ram, the shape of the bow being indicated by faint lines. Having such a solid projection as this at the bow, our ship — provided it can get a chance — would crush in the sides of any wooden vessel at a blow. The Congress offered no more effectual resistance than an egg-shell to the rush of the Merrimac. To be sure the iron prow was, if we are rightly informed, broken off in the collision, seriously damaging the assailant, but this was owing to the faulty method of its construction. We think no casualty of this sort possible in the case of the Roanoke.
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The bow offense being thus provided for, the stern defense must not be overlooked. At the stern are placed the screw, which forms her proving power, and the rudder which directs her. A steamer crippled here becomes a helpless log upon the water. These are protected, as we have seen, in the Monitors by the projecting armor platform; in the Roanoke they are defended by an iron "hood," which looks very much like the shell of a huge turtle, bolted to the ship's side in such a manner that the screw can play freely. The deck must now be covered with iron plates of sufficient thickness to render it bomb-proof, and proof against a plunging fire from the guns of a fortress, and the top of the turrets likewise guarded by proper iron grating. The vessel is now complete, as far as her armature is concerned. She is in effect a floating iron fortress, impregnable, we believe, any assault to which she will be exposed. Of her armament we do not now propose to speak. The subject of cannon must be reserved for another paper.
We now propose to visit a vessel wholly different in plan and model, involving some peculiar principles. This is the "Stevens Battery," which has been for years in course of construction at Hoboken, in New Jersey, just across the Hudson River from New York. We must premise that grave doubts are entertained whether this vessel will meet the requirements demanded by the improvements in offensive warfare made since her plan was formed. But considering the large amount which has been already expended, and the still larger sums which will be required to complete her, we think it proper to present a somewhat minute description of her construction, and of the offensive and defensive qualities which it is claimed she will possess. For this we are wholly indebted to Mr. Watson, whom we have previously made mention. He says:
It was a beautiful afternoon in June when we started on a visit to the Stevens Battery at Hoboken. Arriving at the yard we were courteously received, and at once given the required admission. So down through gardens edged with sweet-smelling box, through green lawns, we went to the coffer-dam, or dock, where she has been lying ever since 1854, now more than eight years. We passed over the narrow gang-plank which boards her, and found beneath our feet a long black massive hull of peculiar and ingenious form. She is a shot-proof vessel of war, capable of great speed and under extraordinary control, throwing a broadside of great weight. The Messrs. Robert L. and Edwin A. Stevens are the designers and inventors, and suggested her to the Government as long ago as 1841. There has, however, been but twenty months work in all upon the battery. The hull is completed, with the exception of some of the deck's bulkheads and minor matters: the engines, propeller-shafting, blowing and pumping machinery, and boilers are finished and in place; the armor, the armament, the decks, the screw-propeller, and upper works are yet to be completed. The cost of the work done has been $728,435, of which Congress appropriated $590,000, the remainder having been advanced by the Messrs. Stevens. Subjoined are some of the details of the vessel:
THE HULL. Length over all 420 feet. Breadth over all 52 feet. Depth from upper or fighting deck 28 feet. Draft of water without coal or stores 17 feet 2 inches. Draft of water with coal and stores 20 feet 6 inches. Fighting draft 22 feet 6 inches.
The vessel is an iron screw-steamer, constructed in the usual way of the best-selected plates, beams, and angle-bars. Her lines are unusually sharp, resembling those of the fastest North River and ocean steamers. Unusual strength of hull is secured by longitudinal bulkheads, by a heavy box-keelson running from stem to stern, and by the shot-proof decks and continuous side armor.
THE ENGINES. Number of screw-propellers 2 Number of engines 8 Diameter of cylinders 3 feet 9 inches. Length of stroke 3 feet 6 inches. Number of boilers 10 Horse power 8600
The screws are under the quarters, or a little on one side of the after-end of the ship, and work independently; each being driven by four compact beam engines entirely below water. For the information of the mechanic we attach a few details which are necessarily technical, for which we hope the non-professional reader will spare us his displeasure. The valve-gear is the link motion adjusted by separate engines as in modern screw-steamers. The engine-frames, eight in number, are in effect cross arches connecting the bottom, sides, and main deck of the vessel: they are composed of wrought-iron plates formed into box-girders on the Britannia Bridge principle. The strength, proportions, and workmanship of the engines are not excelled, it is believed, by any commercial or war steamer. The boilers are of the flue-tubular variety, as used in modern ocean steamboats and the best river steamboats.
THE AMOR. The two leading principles of the vessel for protection from shot and shell are as follows: First. The vessel is settled two feet lower in the water in action, by letting water into compartments arranged to be emptied rapidly by powerful steam-pumps. This is done for the purpose of savin "the weight and cost of two feet of the depth of the armor, which otherwise would be necessary; of allow-in" a flatter slops, and hence a greater resistance of the armor; of employing, to the greatest practical extent, the best known armor — that is, water; of giving the vessel greater speed while cruising, chasing, or retreating, by throwing overboard the weight of water in the tanks, or, in other words, by dispensing with this two feet of water protection; and of enabling her, for the same reason, to pass over bars into harbors which she could not otherwise reach.
Second. The use of inclined instead of vertical armor for the purpose of changing the direction instead of stopping the whole force of the enemy's projectiles. The side-armor consists of a triangular structure of locust timber extending outside the shell of the vessel from stem to
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stem. Its lower slope is plated with iron 3Ë inches thick to a depth of four feet below the fighting line. From the outer corner of this side protection the shot-proof casement or main armor proceeds, upward and in ward, at an angle of one vertical to two horizontal, to a height of 28 feet from the bottom of the ship, and 5Ë feet from the fighting line, where it is covered by a flat shot-proof deck. The main armor extends only over the engine's boilers, blowing and pumping machinery, that is 107 feet forward and 74 feet aft the centre. Its ends slope upward and inward at a similar angle, from the 21 feet deck, which is shot-proof, and which extends forward and aft the armor to the extreme bow and stern. The inclined armor, or casemate, is composed of 6ž inches of iron plates, hacked by 14 inches of locust timber, in which are imbedded six-inch wrought-iron girders two feet apart. The whole is lined with half-inch plate iron. It is supported by the engine frames, by heavy braces, and girders between the boilers, and by the frames and sides of the ship. The horizontal shot-proof decks are composed of 1Ë inches of iron plates, resting on 6-inch wrought-iron girders, filled in with locust timber and backed, with half-inch iron plate.
THE ARMAMENT. This consists of five 15-inch guns, weighing 23 tons each and capable of throwing round shot of 4-25 pounds in weight, and two 10-inch rifled guns. The guns rest on wrought-iron shot-proof carriages, of which the recoil is taken up by India-rubber springs, the carriages are situated on top of the casemates, and are trained by steam-power by means of a shaft passing through the gun-deck to within the casemate. Each gun is loaded with celerity by being pointed to a hole in the deck protected by a shot-proof hood, below which is a steam-cylinder of which the piston-rod is the ramrod of the gun. All the machinery and men for working the guns are thus within the shot-proof armor. The guns are protected by a covering of wrought-iron armor in addition to their own immense thickness — sixteen and a half inches maximum — outside the bore.
THE UPPER WORKS, ETC. The twenty-one feet shot-proof deck, fore and aft the central armor or casemate, affords ample accommodation for men and officers. Above this deck, and flush with the twenty-eight feet gun-deck which forms the top of the casemate, is a light deck, extending at the sides of the casemate, and forward and aft from stem to stern. The entire twenty-eight feet, or gun-deck, is thus level (excepting the usual camber), and unincumbered over the whole vessel. Only the part of it that forms the top of the casemate is shot-proof. Above the twenty-eight feet deck are flying bulwarks to be turned down in time of action. The height of the bulwarks from the water at the load line will be thirteen and one half feet. The fourteen feet deck affords ample space for stores, etc., and for the salt-water tanks for settling the vessel to the fighting line. Below the fourteen feet deck, forward of the boilers, are the blowers and pumping-engines and coal-bunkers. Abaft the engines are coal-bunkers also. Capacity for coal, 1000 tons. The fresh-water for consumption on board will be condensed from the exhaust steam; besides which there will be fresh-water tanks. The vessel will be lighted with gas made on board. The ventilation of the officers and men's quarters will be superior to that of ordinary vessels, as they will be entirely above water. In cruising and in action the entire vessel will be ventilated by the blowers. As the guns are in the open air, and the ship's company separated from them during action by a casemate, the deleterious effects of smoke and sound will be avoided. The ventilation by blowers, the freeing of the vessel from water in the manner proposed, and other operations new to the naval practice of the Government, have been successfully employed by Mr. Stevens for many years. The vessel will have two light masts for emergencies, but will not ordinarily carry sail.
FIGHTING QUALITIES. First. Iron armor 6ž inches thick, backed with 14 inches of the most impenetrable wood, and standing at the acute angle of one in two to the line of fire — that is, one degree of inclination to two of height — is a vastly stronger protection than has ever been applied or found vulnerable by any experimenters at home or abroad. At the same time it is comparatively light, as its extent ia reduced by confining it to the central part of the vessel, and by immersing the vessel to a deeper fighting draft. The parts of the vessel fore and aft the central casemate are also thoroughly protected by a horizontal deck, which is not only shot-proof but one foot below the fighting water-line. The water protection, as far as it can be judiciously employed, is at once the most perfect and cheapest armor.
Second. The side protection, extending from stern to stern, is intended to answer these four important purposes: 1st, Protection from projectiles; 2d, From disaster by collision; 3d, Increasing the immersed beam, and the consequent stability of the ship when fighting; and, lastly, adding in a very great degree to the horizontal and vertical strength and stiffness of the vessel.
Third. the immense power of the engines and the fine lines guarantee a much higher speed than has been attained by any sea-going war or commercial steamer. This vessel will have the entire horse-power of the Great Eastern — with about one-third of her resistance, or twice the horse-power of any war-vessel. The sharpness of her lines is unprecedented in any government practice, and in any except the latest and most successful commercial practice.
Fourth. The ability of the vessel to turn rapidly round on her own centre, without making headway, by means of two screws, instead of occupying the time and making the circuit required by all other war-vessels, will give her remarkable and important facilities for manoeuvring when in action. In connection with her great speed, it will enable her to overhaul one after another of the enemy's fleet within a very short time, to run close alongside an enemy, to present herself for action in the most effective position, to bring her broadside to bear in any direction, to turn round in narrow channels, and, when necessary, to retreat in any direction with facility.
Fifth. The employment of two entirely distinct means of propulsion — the two screws and their respective sets of engines — will enable her to be steered in case of accident to the rudder, and will afford just double the ordinary amount of security against breakage of machinery in fighting or cruising.
Sixth. The employment of barbette guns, or on the top of the casemate instead of within it, gives all of the entire range of the horizon. Three guns can be fired at a time in line with the keel, forward or aft. By setting the guns — by a graduated index-plate within the casemate — so that they shall point at the proper relative angles, and then placing the vessel, either by turning her on her centre or by going ahead or astern, so that one gun bears upon the object to be hit, the fire of all the guns may be instantly concentrated upon that object without losing time in training each gun.
Seventh. The use of the heaviest successful ordnance known not only makes the gun its own armor, but affords the following advantages in fighting the ship: The smashing ing effect of a single heavy projectile upon a single point on the enemy's sides is vastly greater than that of an equal weight of lighter projectiles. In close quarters — a position the vessel is by her speed and manageableness able to assume at option — the velocity of a projectile, that is, its effect, would in like proportion be increased without bringing a greater strain upon the gun. It is believed that a 15-inch gun may carry an elongated projectile of half a ton weight. The smashing effect of such a missile would not only be greater than that of a lighter missile, but more destructive at a low than at a high velocity, according to the representation of military engineers. As there is no casemate over the guns the enemy can pour shot and shell into port-holes at close quarters; for the same reason the guns will not be limited to the few degrees of range permitted by the ports, but can sweep the horizon. The cost and weight of the casemates over the guns are dispensed with, and the seven guns thus arranged will be as formidable as a whole broadside arranged in the ordinary way; and with these remarks closes the description of this battery.