Note for English language Readers: This is the third part (out of four) of the transcription, from the Special Supplement of the SCIENTIFIC AMERICAN, of an study of the strength of the U.S. Navy in 1898; the year of the war against Spain.
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El presente articulo es el tercero de cuatro que completara la transcripción integra, excepto la portada, del Numero 1.165, Vol. XLV, del SCIENTIFIC AMERICAN, fechado el 30 de abril de 1898, que es un Suplemento especial dedicado al estado de la U.S. Navy en aquel año en que se enfrentaría, y derrotaría, a la Armada española.
El citado suplemento tiene 40 páginas y unos ochenta documentos que serán íntegramente transcritos en estos cuatro post.
Aunque es de dominio publico, debido a la fecha en que se publico, hemos solicitado el correspondiente permiso a la redacción de SCIENTIFIC AMERICAN, y nos ha sido concedido.
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Aunque queda un poco fuera de nuestro marco de actuación, la composición de la flota que diezmo la Escuadra del Almirante Cervera es de indudable interés técnico e histórico y ayuda a comprender la debacle. Con lo cual fue también notable en nuestra Vida Marítima.
Algún lector ha enviado una interesante crítica sobre la redacción en ingles de este articulo. Noten los lectores que la traducción del original siempre implica la perdida de valor del documento, por perder la fidelidad exacta en la transcripción, por lo que en el futuro siempre trataremos de dar la copia en el idioma original, rogando de la amabilidad de los lectores el uso de los traductores disponibles en la red,

VOL. XLV. NUM. 1165.
April 30, 1998.
Munn & Co…. Editors and Propietors.
Published Weekly at 361 Broadway. New York.
Catalogue of valuable papers published in SCIENTIFIC AMERICAN SUPPLEMENT furnished free on request.

Protected Cruiser «CHARLESTON.»
The protected cruiser «CHARLESTON» was authorized in 1885, the bill calling for the construction of two cruisers and two gunboats. The ships built under this programme were the cruisers «CHARLESTON» and «NEWARK» and the gunboats “YORKTOWN” and «PETREL.» The plans for the “CHARLESTON” were purchased from the Armstrongs and had to be considerably revised by the builders, the Union Iron Works of San Francisco, the most notable changes being made in the machinery.
The dimensions of this ship are: Length 312 feet 7 inches, beam 46 feet 2 inches, draught 18 feet 7 inches and displacement 3,730 tons. She is driven by twin-screw, horizontal, compound engines of 6.666 indicated horse power. These engines were among the last of this type to be put into a ship for our navy. Horizontal engines were used in the earlier warships to allow of the cylinders being placed well below the water line, but the use of the protective deck, strengthened in the wake of the cylinders and protected by coal bunkers, has enabled the designers to give ample protection to engines of the vertical type. The problem of protection has been simplified, moreover, by the high piston speed now in vogue, and the higher steam pressures, which enable a much shorter stroke to be used, bringing the tops of the cylinders well down to the water line.
The contract called for in indicated horse power of 7,000, with a corresponding speed of 18 knots an hour. On her four hours trial the ship failed to reach the horse power, indicating only 6.666, but she exceeded the speed by 0,20 of a knot, and at times during the four hours run she made as high as 19 knots.
The «CHARLESTON» carries two 8-inch guns, one forward and the other aft, and six 6-inch slow-firers in broadside, the guns being all protected by shields. She has a single large funnel and two military masts. The ship has proved a serviceable cruiser, and during the nine years since she was first put in commission she has been employed on the Pacific coast. She is at present being overhauled at the Mare Island Navy Yard, San Francisco.
Protected Cruiser «BALTIMORE.»
It is just now a fact of special interest that the «BALTIMORE,» at present stationed at Honolulu, was built from plans which were originally offered by the Armstrong Company in competition for the construction of a cruiser for the Spanish government.
They were purchased by the United States government and the contract to construct the ship was let to the Cramp Company, who, after making several changes in the plans, turned out the handsome and very successful protected cruiser “BALTIMORE.” She was authorized in 1886 and went into commission January 7, 1890. The contract called for 9,000 horse power, to be maintained for four hours, and offered a premium of $100 for every additional horse power. The Cramps gave in this vessel the first indication of their ability to largely exceed the contract horse power and speed in ships built at their yards, for the «BALTIMORE” indicated 10.064 horse power and maintained an average speed for five hours of 20,1 knots, thereby winning for the firm a bonus of over $100.000.
The displacement of the «BALTIMORE» is 4,413 tons, as compared with 3,730 tons for the «CHARLESTON,» and the extra 683 tons has been turned to good account. She carries four 8-inch guns in place of the two carried by the «CHARLESTON,» and these are placed some 8 feet higher above the water line, two forward upon a forecastle deck and two aft upon the poop. The six 6-inch guns are carried in the waist of the ship upon the gun deck in broadside. All the guns are sponsoned out on the beam and together they constitute a very powerful battery for a ship of this size. The liberal freeboard of the «BALTIMORE,» the height at which she carries her guns, her speed and general serviceableness render her a popular ship in the navy. When her six 6-inch slow-fire guns are replaced by 5 or 6-inch quick-firers, she will compare favourably with ships of a later date.
The protective deck is 2 ½ inches on the flat and 4 inches on the slopes, as against 2 inches and 3 inches in the “CHARLESTON.” She carries a crew of 386 men, as against 306, and her bunker capacity is 1,144 tons as against 758 tons in the smaller ship. A notable service performed by the «BALTIMORE» was the transfer of Ericsson’s body from the United States to its resting place in Sweden, the great inventor’s native land.
Protected Cruiser «SAN FRANCISCO.»
The protected cruiser » SAN FRANCISCO» and her sister ship the «PHILADELPHIA» were authorized in 1887 the former being built at the Union Iron Works and the latter by the Cramps. The points of difference in the boats are given in the following table: (See attached file)
The contract for both ships called for a speed of 19 knots, and a premium of $50,000 was offered for each ¼ knot above this, a deduction of a like amount to be made for every ¼ knot by which the ships failed to reach the contract speed. The engines were of the horizontal triple-expansion type, the Cramps designing the engines of the «PHILADELPHIA» and those of the «SAN FRANCISCO» being built from government plans. Each ship won a premium of $100.000 for the contractors.
The armament of the two ships is identical. The main battery consists of twelve 6-inch slow-fire guns. Two of them are mounted on the forecastle deck, two on the poop and four are ranged in broadside on the gun deck. Both ships carry their guns well above the water, and when they have been rearmed with quick-firers, as no doubt they soon will be, they will compare favourably in fighting power and speed with later ships.The steel deck in the «PHILADELPHIA» is from 2 ½ to 4 inches thick and in the «SAN FRANCISCO» from 3 to 8 inches. The trial trip of the «SAN FRANCISCO» took place before the masts were stepped or the guns mounted.
The engraving at the top of page 23 shows the vessel as finally completed. Those taken during the trial trip are of special interest, as showing the curious wave line formed when the ship was running at fall speed.
Protected Cruiser «OLYMPIA.»
The «OLYMPIA,» 5,870 tons, has been called a smaller edition of the «NEW YORK,» 8,300 tons; and it is true that in armament, speed and handsome appearance there is a certain likeness. It must be remembered, however, that they are not of the same type, the ‘»OLYMPIA» having no side armor and, therefore, coming in the class of protected ships.
There is a certain respect in which the «OLYMPIA» can easily challenge comparison with any other protected cruiser, either in our own or in any other navy of the world. We doubt if there is any protected ship which can show on a given displacement so high a development of the various qualities which go to make up the efficiency of this type of warship. The genius of the naval designer will be shown in the manner in which he distributes his weights; and the most successful ship will be that which secures a high all-around efficiency without the sacrifice of any one essential feature. It would be an easy matter, comparatively, to build a ship which should be at once the fastest, best protected, most heavily armed, and have the greatest coal endurance of any ship in the world—provided there were no limit upon displacement. The «COLUMBIA» can steam 23 knots against the «OLYMPIA´s” 21,68 knots ; but to get this 1 1/5 knots of extra speed she has had to sacrifice her offensive power to such an extent that she would be an easy prey to the smaller ship in a naval duel. Judged by the ships which have lately been produced, the United States designers are considerably ahead of those of foreign navies in their ability to turn out ships with an all-around efficiency. A comparison of the «OLYMPIA» with the new «ECLIPSE» class of British cruiser, built from government designs, will show this very clearly.
The great superiority of the «OLYMPIA» over the «ECLIPSE» on every point of comparison cannot be attributed to the extra 200 tons displacement of the former. The main battery of the «OLYMPIA,» composed or four 8-inch and ten 5-inch breech-loading rifles is entirely on the main deck. The four 8-inch guns are mounted in pairs in two turrets of Harveyized steel 3 ½ inches thick, revolving within barbettes of 4-inch nickel steel armor. Firing through an arc of 208 degrees and having an axial height of 22 feet, these guns have a great range of action, besides being unusually well protected from return fire.
The ten 5-inch guns, which are of the rapid-fire type, are housed in armored sponsons 4 inches thick, and are so placed that they give a direct bow or stern fire from four guns and a broadside discharge on either side from five.
The secondary battery, composed principally of fourteen 6-pounder rapid-fire guns, is stowed in armored sponsons on the gun deck and along the hammock berthing above the 5-inch guns, affording the greatest convenient range and command. The disposition of the 6-pounders on the berth deck is such that, while free from the flash of the main battery above, they may maintain a complete belt of fire around the ship. The seven 1-pounders and the four Gatling guns, which constitute a minor phase of the secondary battery, are distributed in the fighting tops and at advantageous points on the bridges. There are six torpedo discharges; one at the bow, one at the stern and two on each broadside.
The vessel has twin screws, each shaft being driven by its own vertical triple-expansion engine. While not admitting strictly of comparison, the «OLYMPIA» and the «MINNEAPOLIS» have engines individually alike, one having two sets and the other three. On trial, the “MINNEAPOLIS» developed nearly 21.000 horse power, a proportion of 7,000 for each engine; and the “OLYMPIA” developed 17.313 over 1,600 horse power more in each engine than was realized by the larger craft The «OLYMPIA» was built by the Union Iron Works and since her commission has done duty in Pacific waters. She is now the flagship at Hong Kong.
Protected Cruiser «DETROIT.»
The three unprotected cruisers «DETROIT, » MARBLEHEAD» and «MONTGOMERY» were authorized in 1888. The first and last were built at the Columbian Iron Works, Baltimore, and the «MARBLEHEAD» at City Point Works, Boston.
Unprotected cruisers rely solely upon coal and a very minute subdivision of the compartments in the region of and below the load line for protection against serious injury. This is further secured by cofferdams worked in the vicinity of the machinery spaces and filled with cellulose -or other water- excluding material to prevent the water, in case of injury, from finding its way to the larger compartments in the center of the vessel.
All the machinery, dynamos and magazines are placed beneath a watertight deck of thin plating, which at its outboard ends is some three feet beneath the water line, but rises considerably above it in the central portions. The object of this deck is not so much to afford resistance to a shot from an enemy, but to allow the side of vessel to be pierced near the load line, or even below it, without flooding the compartments containing the boilers, engines and magazines. The dimensions are as follows: Length, 257 feet; beam, 37 feet; draught, 14 feet 7 inches; displacement, 2,089 tons.
The armament of ten 5-inch rapid-fire guns is carried as follows: One each on the forecastle deck and the poop, two in wide sponsons on each broadside, giving dead ahead and astern fire, and between these are two other 5-inch guns on each broadside. The trial speed of the «DETROIT» was 18,71 knots. As these boats are intended for long cruises on distant stations, they are furnished with specially roomy accommodation for officers and crew.
Protected Cruiser “NEW ORLEANS.”
The «NEW ORLEANS,» formerly the «AMAZONAS,» of the Brazilian navy, is one of two vessels recently purchased by the government from Brazil. The sister ship, which is not yet completed, will be known as the «ALBANY.» These vessels were ordered from the Armstrong Company, Newcastle, England, by the Brazilian government, and at the time of their purchase the «AMAZONAS» was in commission and about to sail for Brazil.
The «NEW ORLEANS» is a typical boat of the kind turned out by the builders, and exhibits the characteristic qualities of good speed and abnormally heavy battery, comparing in this respect with our own «CINCINATI.» The principal dimensions, etc., of these twin ships are as follows: Length, 330 feet; beam, 43 feet 9 inches; draught, 16 feet 10 inches; displacement, 3,600 tons. They have twin screws and engines, the horse power being 7,500 and the speed 21,05 knots. Their normal coal supply is 700 tons, though they have stowage room for more. They are protected by a Harvey steel deck which is 3 inches thick where it curves down below the water line along the sides.
The battery is, for the size of the ship, very powerful. It is not only powerful in numbers, but owing to the fact that its guns are of the latest pattern, they have vastly greater power for their size than guns that were built only four or five years ago. Armstrongs are builders of both the wire wound and the hooped types of gun, and the weapons turned out by this firm have shown very high ballistic results. Not only are these guns more powerful for their weight, but they have improved breech mechanism which enables them to be fired with greater rapidity.
The following comparison of the «NEW ORLEANS» with a ship of the same size and type built for the British navy from government plans shows clearly the greater fighting power of the former. The figures are taken from the official tables of the British navy and the firm of builders. The speed of fire is that actually obtained by crews on board ships in commission. The «INTREPID» is one of a class of thirty ships built under the late Naval Defense Act, and though not so up-to-date as the «AMAZONAS,» may be considered as a good example of the average protected cruiser of the existing navies of the world.
From this comparison then it is evident that although the two ships are of the same size, the » NEW ORLEANS» can deliver from her broadside more than double the energy of shell fire that the «INTREPID» can, although the latter ship was built only five years in advance of the former such is the rapidity with which naval science and construction advances. The increased energy is due to increased velocities resulting from the greater length of the guns and the use of improved powders.
As further illustrating the development in naval design in a brief five years, we append below a further comparison.
We find, then, that by the use of improved materials and methods the naval architect has been able, out of the same capital (3.600 tons displacement) to produce a ship having superiority on every point of comparison—a ship with more speed, with 50 per cent better protection, 80 per cent larger coal capacity, and over 100 per cent more powerful armament.
The transfer of the ship took place at Gravesend, at the mouth of the Thames, England, when the ship was formally handed over by Commander Corres, of the Brazilian navy, to Lieut. Colwell, of the United States navy. The Brazilian flag was hauled down and the stars and stripes were run up, accompanied by a salute from the old fort at Tilbury, whose guns had not spoken for two centuries past. (See attached file)
The monitors of our navy form a connecting link between the early and later systems of armored warship construction. They embody in their original design the lessons which had been learned in the naval operations of the civil war, and, as their name implies, they are modeled after the pattern of Ericsson’s famous «MONITOR.» The chief characteristics of this type of ship are moderate speed, low freeboard, making them a difficult object to hit, thick armor, and an armament of a few exceptionally heavy guns. Sitting low in the water, they are not suited for work on high seas, and their sphere of operations lies within sheltered waters, such as are found in our bays and harbors. This is their proper sphere of action, and to enable them to manouver in shoal waters they are designed to have as little draught as possible.
Strictly speaking, they are floating batteries, and as such they are intended to co-operate with the land batteries in defense of our coasts. But though the monitor is designed specially for harbor defense, it would be quite capable of taking part in a fleet action off the coast in ordinary weather.
The formidable little warship which forms the subject of the accompanying illustrations is one of a group of five similar vessels whose keels were laid as far back as the year 1874. In the official lists of the navy they are described as iron low-freeboard coast-defense monitors. With the exception of a few small gunboats, they represent the only new construction attempted in the navy during that long twenty years intervening between the close of the civil war and the date of the construction of our modern navy.
The building of even these five ships was carried on slowly, and it was stopped before they were completed. The shells of the ships, with their engines on board, but with no armor or armament, were laid up, and it was not until March 3, 1885, that an appropriation of $3,178,046 was made for their completion. Of the five monitors, three, the «MIANTONOMOH,» «MONADNOCK» and «TERROR,» are sister ships to the “AMPHITRITE”,» which is of 8.990 tons displacement, the «PURITAN” being considerably larger, 6.060 tons, and carrying 13-inch, against the 10-inch guns of the smaller ships.
There is another monitor, the «MONTEREY,» similar in design but more modern in construction, which was built by the Union Iron Works, at San Francisco, and is now stationed on the Pacific coast.
The hull of the «AMPHITRITE» is built of iron: It is constructed on the cellular system, and the double bottom rounds up into the sides to within 3 feet of the water line, where it forms a shelf on which is carried the armor belt. This is 7 feet high, and reaches to the main deck, 4 feet above the water line. The belt tapers in thickness from 9 inches amidships to 5 inches at the ends. The main deck is of l ¾ -inch steel, overlaid with wood. The barbettes and turrets are of Harvey steel, with a thickness of 11 ½ and 7 ½ inches respectively. The roof of the turret is plated with 1 ½ -inch steel. The conning tower is of 9-inch Harvey steel. It stands just abaft the forward turret. Immediately above it is the chart house, and above this the flying bridge. Between the two turrets is the superstructure, which carries upon its deck two 4 inch rapid-fire guns, two 6-pounders, two 3-pounders, and two 1-pounder rapid-fire guns. We give two illustrations of the 4-inch guns, which, although they are of comparatively small size, are among the most effective and handy weapons in the navy. They are mounted on steel carriages which rotate on a circle of rollers carried by a cast steel pedestal which is itself fierily bolted to the deck. A semicircular shield 2 inches thick is attached by brackets to the top carriage and rotates with the gun. The shield reaches well down over the pedestal and affords full protection to the gun mount and the crew. The gun, carriage and shield are so evenly balanced that the piece can be trained and elevated with the greatest ease. The illustration taken from the rear shows the breech mechanism, the recoil cylinder beneath the gun and the sights. The training is effected by the crank wheel at the side and the elevation by the worm and pinion, which can be seen in the side view of the gun.
The main fighting power of the «AMPHITRITE» lies in her four big 10-inch guns, which are mounted in pairs within the main turrets. This gun weighs 25 tons and fires a 500-pound shell at a velocity of 2,000 feet per second. It can penetrate 18,75 inches of steel at the muzzle, 16,82 inches at 1,000 yards and 15 inches at 2,000 yards.
The «AMPHITRITE” is driven by the original twin screw engines designed in 1870. They are of the direct acting inclined compound type, and the arrangement of the cylinders and cranks is very interesting as showing how the designers contrived to stow away such large machinery below the level of the protective deck.
The cylinders which drive the port propeller shaft are located above the starboard shaft, and vice versa, the engines thus crossing each other diagonally. They are of 1,600 indicated horse power, and will drive the «AMPHITRITE” at a speed of 10,5 knots per hour. She carries a complement of 183 all told.
Monitor «TERROR.»
The monitor «TERROR» differs from the «AMPHITRITE» in having no barbettes, the turrets projecting directly above the main deck. In this respect both she and the «MONADNOCK» are inferior to the «TERROR» «PURITAN» and «MONTERREY,» which have an increased command of their guns, due to a low barbette. There has lately been installed on the «TERROR» a compressed air system for loading and manipulating the guns and steering the ship, which is spoken of very favourably in the last report of the Secretary of the Navy. The use of compressed air as a motive power on board a warship presents several advantages over steam or hydraulic power which render it a powerful competitor. As compared with steam, it is less dangerous, especially during an action, when a broken steam pipe might prove terribly fatal, and it enables certain parts of the ship to be kept at an oven temperature, which would otherwise be rendered uncomfortably hot by the presence of steam piping. Steam and hydraulic engines, moreover, require exhaust pipes discharging outside the hull of the ship; whereas the exhaust from the pneumatic cylinders may be turned into the ship or into the outside air, as may be most convenient.
There are certain localities in a ship where the exhaust from a pneumatic engine would prove a valuable source of ventilation, as, for instance, in a turret crowded with men and machinery, or in the close confinement of a steering room situated below the protective deck. As compared with hydraulic power, the compressed air system is cleaner and more convenient, and free from the discomfort that arises from the leaking of hydraulic pipes and cylinders.
The air for driving the various pneumatic devices is compressed by two separate engines, which supply sufficient air for turning the turrets, elevating the guns, lifting the ammunition into the cages, raising the cages to the breech of the gun, ramming home the charge, closing the breech, checking the recoil, and lastly, and most important operation of all, steering the ship itself.
The two turning engines are placed upon the floor of the turret, one on each side of the big guns. Each engine has two cylinders, 8 inches in diameter by 14 inches stroke. A worm on the crank shaft operates a set of gears by which the power is multiplied many times over before it reaches a driving pinion, which, in common with the engine and gears, is firmly bolted to the framing of the turret and of course turns with it. The pinion meshes with a large circular rack which is bolted to the deck of the ship and lies immediately within the circular steel track upon which the turret rotates. The engines are controlled by suitable levers and hand wheels situated within easy reach of the officer in the sighting hood, the latter being placed over and between the guns, as shown in the sectional view, page 39.
The elevation and depression of the gun is effected by means of a massive ram, which is hinged to the floor of the turret and bears against a shoe on the under side of the gun carriage near the breech of the gun. On each side of the turret is a cylinder containing glycerine and water, a portion of which, when the gun is to be elevated, is forced by compressed air into the ram, the supply being regulated by valves which are operated by means of levers in the sighting station above mentioned.
By reference to the large sectional view of the turret the reader can obtain a clear idea of the method adopted for sighting the great 10-inch guns. From the forward end of the massive gun carriage a small vertical rod is carried up to a bell-crank lever situated near the roof of the turret. Another rod extends from the short arm of the lever and is connected to another bell-crank lever attached to the sighting hood. The long arm of this lever carries a sighting telescope which is placed opposite one of the narrow horizontal slits which are cut through the side of the hood. The system of levers is so proportioned that the axis of the telescope and the axis of the gun will always be parallel, any change in the elevation or training of the gun being accompanied by a similar change in the position of the telescope.
With his eye at the telescope and his hand upon the levers which control the air valves of the turning and elevating machinery, the officer brings the cross hairs of the telescope to bear upon the mark, and by pressing ah electric button hurls a 500-pound steel projectile with unerring precision at the hostile ship.
Immediately below the turret is the handling room, adjoining which are the magazine and the shell rooms, with which it communicates through doorways which, when not in use, are closed by watertight doors. Directly below the center of the turret is a pneumatic loading machine, which rotates upon a vertical shaft, and may be swung to the right or left as desired. The 500-pound shell and the cartridge, the latter in two parts, are run out from their respective rooms on an overhead trolley and placed in the tray of the loading machine, as shown in the illustrations. The tray is pivotally attached to the body of the machine by a set of parallel rods and a lever which carries at its inner end a circular rack. Above the rack is an air cylinder whose piston rod terminates in a vertical rack which engages the circular rack before mentioned. By admitting air at the top of the cylinder, the tray with its load is raised to the required height and the latter is placed in the pockets of the loading car.
There are two of these cars, one for each gun, and they travel upon two vertical hoists or trackways which lead up to the breech of the guns.
The hoisting is done by two pneumatic cylinders located on the floor of the turret between the guns. By reference to the first illustration on this page, it will be seen that the loading car contains three parallel pockets, which rotate within the frame of the car, friction wheels being interposed to facilitate the movement. One of the pockets carries the shell and the other two the powder charge. The car is automatically brought to a stop with the lowest pocket containing the shell immediately in line with the breech of the gun.
The shell is pushed home by a telescopic rammer which is operated by compressed air, the valve which admits the air being worked by a man who sits astride of the cylinder. It will be noticed that the rammer is carried by a bracket bolted to an extension of the gun carriage, and it is consequently held at all times in true line with the bore of the gun. After the shell has been rammed home, the loading car is rotated and the two sections of the powder cartridge are brought successively opposite the breech and pushed home. The breech plug is then swung round, thrust into place and locked.
The recoil of the gun is controlled by two pneumatic cylinders, 14 inches in diameter and 40 inches in length. The cylinders, whose heads can be seen in the smaller illustration, page 38, below the breech, are secured to the gun carriage and the pistons to the gun. Before firing, the pressure on the recoil side of the pistons is about 500 pounds per square inch. As the gun recoils, carrying the pistons with it, this pressure is rapidly increased by compression. To reduce the pressure at the end of the recoil, a tapered rod is provided, which passes through the center of the piston and allows the air to pass more and more freely to the counterside of the piston as the gun returns. The residual pressure is utilized to return the gun to its firing position. Perhaps there is no part of the many operations performed by compressed air on the «TERROR» in which the power shows to better advantage—the elasticity of the air preventing all shock and providing an easy cushion in the recoil and counter recoil.
The last and most important duty performed by the compressed air is that of steering the ship. The interior of the steering room is shown on page 30. The work is performed by the two long horizontal cylinders which will be noticed arranged one on each side of the tiller. They are provided with a common piston rod in the center of which is a hollow crosshead in which the tiller is free to slide as it is swung right or left by the movement of the pistons. Compressed air is admitted to the outer ends of the cylinders by means of a valve, the air being simultaneously admitted at the back of one piston and exhausted from the other, according as the helm is to be put over to port or to starboard. Air is also admitted at all times at the inner ends of the cylinders, and a pipe connects them, so that, as the pistons move, the air may flow freely from the inner end of one cylinder to the inner end of the other. In the center of the connecting pipe is a bypass valve, which is open when the tiller is being-moved but closes when it has been traversed the desired angle and holds the air imprisoned in the cylinders, thus locking the tiller between two elastic cushions. The heavy shocks to which the tiller is subject in rough weather will thus be received and absorbed by the air, and the framing of the ship will be proportionately relieved of the strain.
For the constructive details of the hull and engines the reader is referred to the description of the sister ship «AMPHITRITE.»
Monitor «MONTEREY.»
At the time when it was finally decided to complete the four old monitors whose keels were laid in 1874, the construction of a new monitor, the «MONTERREY,» was authorized.
The contract was secured by the Union Iron Works, San Francisco; the keel was laid in 1889, and the vessel went into commission February 13, 1893. While this powerful vessel is a monitor pure and simple, she embodies all the latest improvements in warship construction, and constitutes one of the most powerful coast defense vessels of the new navy.
The principal dimensions etc., are: Length, 256 feet; beam, 59 feet; draught, 14 feet 10 inches. She is constructed entirely of steel; the belt is 13 inches thick amidships and tapers to 8 inches at the bow and 6 inches at the stern. A continuous deck of 3-inch steel extends from stem to stern. Further protection is afforded by a double bottom and watertight bulkheads, the hull containing 110 separate watertight compartments. The heavy guns are carried in turrets and the turning gear, etc., are protected by barbettes. Forward, the turret is 8 inches thick and the barbette 18 inches and within the turret are two 13-inch guns. The after turret is 7 ½ inches and the barbette 11 ½ inches, the after guns being of 10 inches caliber. The ship carries a single military mast, in the fighting top of which is placed a part of the rapid-fire battery. The balance of the rapid fire guns are carried on the superstructure deck between the turrets.
We give two illustrations of the twin triple expansion engines, which indicated 5.244 horse power on the trial trip. The cylinders are 37, 41 and 64 inches diameter respectively and 30 inches stroke. The high pressure cylinder is forward in each engine, and has one piston valve 14 inches in diameter, the intermediate pressure cylinder having two of 14 inches and the low pressure cylinder two of 20 inches, all worked by Stephenson double-bar links. The cylinders are supported by cast steel inverted Y frames secured to cast steel bed plates. The crank shaft is of forged steel, in three interchangeable sections, with 4-inch axial holes through shafts and, crank pins. The journals and crank pins are 11 inches diameter. The line, thrust and propeller shafts are 10 inches in diameter, with a 4-inch axial hole. The screw propellers, of manganese or aluminium bronze, are three-bladed, and are 10 feet 6 inches in diameter, the starboard one being right and the port one left handed.
The condensers are cylindrical, and have about 3,850 square feet of cooling surface in each. The circulating pumps are centrifugal, with a capacity of 5,000 gallons per minute each, and connections for working as wrecking pumps. Each condenser has two vertical single-acting air pumps, 14 3/8 inches diameter by 15 inches stroke, driven by a compound engine with a fly wheel at each end of shaft. There is a valve in the exhaust pipe from each low pressure cylinder, to shut off the connection to the condenser and permit it to be used as an auxiliary condenser when the main engines are stopped. The engines are fitted with starting valves, a steam-actuated throttle, and a combined steam and hydraulic reversing gear, so that they can be handled-with ease, and there are the usual auxiliary engines.
In order to reduce the weight of the machinery to the lowest limit, the engines have been made as light as possible, and about three-fourths of the required boiler power is supplied by coil or tubulous boilers.
Four boilers of the latter class, to give a collective horse power of 4,500, were contracted for with Charley Ward, of Charleston, W, Va., after careful trials.
The two cylindrical boiler with which the vessel is also to be supplied are fitted to work at 160 pounds and are designed to give sufficient steam for ordinary uses, for propelling the vessel at 10 knot speed, while the coil boilers enable steam to be raised in less than half an hour in sufficient quantity to give the maximum speed of which the vessel is capable.
The illustration below shows the “MONTERREY” in the new dry dock, on Puget Sound, Wash. The photograph was taken on the occasion of the opening of the dock on April 22, 1896