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1820. In 1850, Mr White tells us,* factorily compensated and corout of 133,700 tons of shipping rected. added to the British Mercantile As to comparative lightness, the Marine, only 12,800 tons, less than percentage of nett to tare displaceone-tenth, were iron ships. In ment has been materially im. 1860, out of 212,000 tons added to proved by the introduction of iron the navy, 64,700 tons, nearly one- as a material. In wooden merchant third, were iron ships. In 1875, ships, the weight of the hulls were out of 420,000 tons of newly-built from 35 to 45 per cent. of the ships, 374,000 tons, nearly nine- total displacement, leaving from tenths, were built of iron. If 55 to 65 per cent. for the cargo. steam-vessels alone are regarded, In iron merchant ships ten per the change is still more complete. cent. of the former division of During 1875 a tonnage of 179,000 weight is deducted from the hull, was added to British steam and added to the cargo. In the shipping, and of these 176,000 tons mastless type of ironclad war were iron built.
vessels the weight of the hull is Iron shipbuilding originated in from 30 to 35 per cent. of the disEngland, and has received its most placement, leaving 65 to 70 per cent. important development in English for the cargo; and in the Russian dockyards. It has rendered the circular type the proportions are country independent of foreign stated at 20 and 80 per cent. powers for the supply of materials respectively, of the total floating for its navy. All the ships added power. to the Royal Navy within the last The size of vessels has increased ten years have iron hulls, and not in proportion to the greater power a single wooden vessel is now in given to the constructor by the use course of construction for the of iron as a material for shipRoyal Navy.
building. The St. Vincent, one of The special advantages of iron, our largest men-of-war in 1815, as compared with wood, are thus was 205 feet long, 53 broad, and stated : 1. Superior lightness com- had a displacement of 4700 tons. bined with strength ; 2. Superior The Inflexible, the latest type of durability, when properly treated; mastless sea-going men-of-war, has 3. Superior ease and cheapness of a displacement of 11,400 tons; her construction and repair; and, 4. dimensions are 320 feet by 75, and Superior safety, when properly her engines work to an indicated constructed and divided into com.
power of 8000 horses. The Great partments. On the other hand, it is Eastern, completed by Mr. Brunel admitted that the bottom of an iron in 1858, had a length between vessel is more easily damaged by perpendiculars of 680 feet, a contact with rocks or shoals; and breadth of 83 feet, a depth of that the fouling of the bottom, 58 feet, and a displacement, at and consequent loss of speed, is 30 feet draught of water, of 27,419 more rapid in an iron than in the tons; the engines were of 2600 case of a wooden vessel. One nominal, working up to 6600 indifeature of the iron ship, which at cated, horse-power. The weight one time seemed likely to render the of the hull, as launched, was use of the material altogether un- 11,000 tons. suitable—that is, the disturbance The use of iron as a material for of the compass-has been satis. shipbuilding has had two distinct
* Manual of Naval Architecture, p. 364.
phases. The first was that to and the thickness of a wholly which we have referred, as intended armoured vessel of this capacity, to insure greater lightness, strength, constructed so as to have the and capacity. The second was a largest amount possible of buoystep in a very different direction. ancy. It contemplated the increase of the It will be observed that it is not efficiency of a ship as a man-of- the case that this mode of conwar, by rendering it more or less struction has as yet been used in impenetrable to the shot, and our dockyards. The idea of a especially to the shell, of the circular ship is taken from the enemy.
Russian navy; and Mr. Froude Mr. Reed, in a paper read at the pointed out, during the discussion eighteenth session of the Insti- cited, that the resistance to the tute of Naval Architects, on the passage through the water of such 22nd of March, 1877, stated that a vessel would be three times that a hemisphere of iron, forming of one constructed on more shipa shell of 100 feet in diameter, and shape lines. It is only at and 28 inches thick, would just float. above the water-line that solid The displacement would be 7480 armour has been hitherto applied. tons. But the draught of 50 feet But Mr. Reed contemplates the of water is too much for any ship. probability that it will hereafter If the depth be reduced, by flatten. become necessary to plate the keel ing the bottom, to 20 feet, the of a war ship heavily, in order to vessel would no longer float, as the resist torpedoes. The deck must buoyancy will have diminished be no less strong, in order to resist more rapidly than the weight. The vertical fire. The limits of flotadisplacement will then be reduced tion are therefore pretty clearly to 4250 tons, and, in order to make indicated, and are not very narrowly the vessel float, the thickness must to be approached. Had a vessel of be reduced to 19 inches. But the the given displacement of 4250 least wave would sink a vessel of tons been constructed 245 feet long, such exact equilibrium. The dis- and 40 feet wide, Mr. Reed says placement would support the deck that the thickness of the armour alone, leaving no buoyancy for must be from 51 to 6 inches less vertical sides, bulwarks, deck, than that of the before-mentioned armament, cargo, and crew. To “soup-plate” pattern. We are provide engines and boilers of an thus driven to suppose an enormous indicated horse-power of 3600 displacement necessary for any horses, 600 tons weight must be vessel that is to be covered, above, added, and an equal amount for below, and on her sides, with more coals. The weight of 1200 tons than 12 inches of iron. The limit would be equal to that of about of size and of resistance is readily 54 inches of iron all over the shell. attained. The limit of cost will But we have seen that the hull be no less restricted. displacement of a war ship should On 26th September, 1854, Capt. not exceed 35 per cent. of its total Ericsson, formerly well known in displacement. We can, therefore, England as a competitor with afford only 1500 tons for the George Stephenson for the prize weight of the hull, which would for a locomotive engine offered by reduce the general thickness to a the Liverpool and Manchester little under 10 inches. This, then, Railway Company in 1829, formay be taken as indicating a limit. warded to the French Emperor ing proportion between the size Louis Bonaparte a design and
specification of an irod-clad steam of iron. The midship section is battery, with revolving cupola. triangular, with a broad hollow The object which the inventor keel, loaded with about 200 tons of desired to achieve was the solution cast-iron blocks to balance the of the following problems: 1. The heavy upper works. Thus careconstruction of a self-moving, shot fully did this great engineer proproof vessel. 2. That of an instru- vide against such a disaster as the ment capable of projecting very capsizing of the Captain. The large shells at slow velocities, but ends of the vessel are moderately very accurately, in accordance with sharp. The deck, made of iron, is previously determined rate. 3. A curved both longitudinally and shell not subject to rotation in the transversely, the curvature being direction of its course, and so con- 5 feet; it is made to project 8 feet trived as to explode with infallible over the rudder and propeller. certainty at the instant of contact. The entire deck is covered with a 4. A shell capable of being pro- lining of sheet iron 3 inches thick, jected under water (or what is now with an opening in the centre of called a torpedo), certain to explode 16 feet in diameter. Over this on contact, together with an instru- opening is placed a semi-globular ment for projecting such a shell turret of plate iron 6 inches thick, from the vessel at a certain depth revolving on a vertical column by below the water line.
means of steam power and approThe idea of a submarine shell, or priate gear work. The vessel is mine, had been not only struck propelled by a powerful steamout, but carried to a high degree of engine and screw propeller. Air perfection, in 1810, by Fulton, who for combustion under the boiler also designed a boat which would and for ventilation is supplied by sink at will and move beneath the a large self-acting centrifugal surface of the water, in order to blower, the fresh air being drawn approach the vessel which it was in through numerous small holes intended to attack without being in the turret. discovered. On 20th August, 1842, A tube for projecting the shells Colonel Samuel Colt utterly of 20 inches diameter of bore, was destroyed a schooner given for the placed on the platform of the repurpose of experiment by the volving turret. It was loaded Government of the United States through a valve, and the shell was on the Potomac River, while to be projected by the direct action stationed himself no less than five' of steam from the boiler. Two miles from the scene. Colonel similar tubes were placed in the Colt claimed to possess a secret, body of the vessel, at a fixed which died with him. But the inclination of 22°, revolving on peculiarity of Ericsson’s vessel was, vertical pivots. The shell was not that it should approach an of cast iron, with a tail of thin enemy unseen, or indeed under plate iron in the form of a cross water, as was the case with attached, to prevent rotation in the Fulton's torpedo boat, but that it line of flight. A percussive ham. should be an iron-clad battery, mer and wafer were attached to self-moving, and strong enough to the anterior part of the shell, giving resist the shot that would be an explosion at the moment of directed on it from the enemy it contact. The hydrostatic javelin, wished to destroy.
or torpedo carrier, for the disThis forlorn hope of the war navy charge of a shell under water, is of the future was composed entirely described with no less minuteness. On April 5, 1862, Capt. Coles the French had gunboats of about stated, in a letter to the Times, 2000 tons displacement, 172 feet in that his experience in the Baltic length, 43 feet beam, and 17 feet and Black Seas, in 1855, suggested deep, protected by 44in. plating, to him the idea of building impreg- while each mounted sixteen guns, nable vessels; and that towards all of which could be fought from the latter part of that year he had one side. They were frequently 2 rough model made by the car- struck by shot, and received no penter of the Stromboli. Capt. severe injury. During three months Coles consulted Isambard Brunel, in the summer of 1863, according who before this time had expressed to reports from Admiral Dahlgren, to the writer of this paper the eight of the monitors invented and decided opinion that the first great
introduced into the U.S. navy by object which the artillerist chiefly Captain Ericsson, received, without required at that time was to be injury, 1030 shot from the enemy, able to insure the explosion of a while themselves firing a total shell exactly at a given moment of number of 2332 11-inch and 1255 time, whether by percussion or by 15in. projectiles. Ericsson's first any other means. The fact which
monitor, built in one hundred days has hitherto checked the develop in 1861, was 172 feet long, with 41 ment of the torpedo, and to some feet beam, 117 feet hold, and 1255 degree rendered the shell a less tons displacement. Her armour fatal implement for the artillerist consisted of superposed sheets of than would otherwise have been iron one inch thick. the case, namely, that a loss of The earliest English ironclad, the time occurs between impact and Warrior, was completed in 1861. explosion, was then pointed out by She had 4, inches iron, and a disMr. Brunel as the result of his own placement of 6000 tons. The reflections, before any of the ex
of the Bellerophon is periments were made which so 6 inches, with a tonnage of 4270 fully justified the preformed anti
that of the Hercules, launched cipations.
in 1868, 9 inches, with 5234 tons Mr. Brunel gave Capt. Coles the tonnage. The load displacements of aid of his draughtsmen; and in these three vessels are respectively March, 1859, drawings were com- 9137, 7551, and 8677 tons. The pleted of “a shield fitted with turn- thickness of armouring has intables." In December, 1860, Captain creased, together with the inColes published, in Blackwood's crease of skill in manipulation, Magazine, drawings of his gun and also that of power in the shield and working platform, the gun.
The iron plates experiplatform being turned by manual mented on at Spezia were of the power only. There seems to be no extraordinary thickness of 22 reason for suspecting that Captain inches. The projectile of the 10Coles had in any way taken a hint inch gun penetrated 14 inches into from Captain Ericsson, or become this plate, which is regarded as its aware of the suggestion made by full power of penetration; but Com- . the latter to the French Emperor mander Grenfell
, R.N., in a paper in 1854. But comparisons of the on cast iron and steel read before above dates show the absolute the Institute of Naval Architects priority of Ericsson’s ironclad, on March 23, 1877, says: “We however distinct may be the origi- should not be too hasty in declaring nality of that of Captain Coles. the impossibility of employing far
During the Crimean war, in 1855, greater thicknesses than any yet
given, should the necessity of the 38,316 foot tons. If the same rule defence demand it. The next ten were applicable to so tremendous years may see the introduction of a shock as that which has been cannon which shall bear the same found approximately to hold good relation to the 22-inch plates of the in the series before mentioned, at present that these do to the 4,-inch least 30 inches of solid iron armour plates of sixteen years ago." It is, would be required to oppose penehowever, rather to the defence of tration from such a missile. land forts than to that of sea-going It has thus become apparent to vessels that the_gallant officer the naval constructor that the day probably refers. For resisting the of wholly - armoured vessels is projectile of the 100-ton gun a nearly over.
The increase of prothickness of about 4 feet of cast jectile power is already so great iron chilled on the outer side is sug- that no ship, of whatever form gested by Com. Grenfell. The pro- may be proposed, could swim if portions of targets to guns are clad in armour which would be shown by Mr. E. H. Knight in his impenetrable to the projectiles of “Practical Dictionary of Mechan- guns that are now ready for use. ism,” from the thickness of 4 inches The mode, therefore, in which the of iron, backed by 18 inches of designer of floating batteries is timber and a 11-inch skin of iron, now endeavouring to keep out the which has been pierced by a 7-inch shot is this. A central citadel, of gun with a 30lb. charge, throwing an adequate thickness to resist the a 115lb. projectile 1200 yards; up expected blow of the enemy's shot, to a 16in. plate, with 18-inch back- is to be constructed, and an uning and 14-inch skin, pierced by the armoured prow and stern are to be 700lb. bolt of the 12-inch 35 ton attached, which shall be so lined gun at 500 yards.
with compartments filled with cork The penetrating power of this as to preserve flotation and staseries of weapons rises from 54 bility even if riddled with shot. foot tons per inch of the circum- For the central citadel it is evident ference of the shot in the first that independent stability is necesinstance, to 188 foot tons in the sary. Not only must it be strong last. But the mighty race has enough to resist horizontal and advanced rapidly since the publi- vertical fire, but, as Mr. Reed antication of this well-designed table. cipates, it must be armoured below. The powder chamber of the 100- It is not, indeed, proposed that ton gun at Spezia has been en- this floating castle should be also larged, and the use of cake, or very navigable; the navigability is to large-grained, powder has enabled depend on the unarmoured part. the artillerist to increase the But the citadel must be able to muzzle velocity of the 2000lb. float, independently of any aid projectile, with a reduction of the from the rest of the ship; and, not tearing strain on the interior of only so, but she must possess a the gun. By the enlargement of degree of stability suficient to the chamber, the muzzle velocity prevent any danger of her being has been increased from 1424 to capsized by a shock such as that 1585 feet per second, and the which her armour is intended to energy of the projectile from
resist. It is evident that the 28,130 to 34,836 foot tons. With elements of the problem are such the coarse powder, a velocity of as to render the solution a matter 1661.5 feet per second has been of very great nicety. attained, giving an
But let us see whether we are