THE BRITISH NAVAL MANOEUVRES FOR 1894.
[ENGINEERING.]
The official account of the partial mobilization and naval manoeuvres of last year has just been issued. It is a brief document, dealing in a summary method with the operations of the two fleets. It appears that 96 vessels of all classes were engaged, 24 of these being torpedo-boats and 26 small special service vessels. There were 33 cruisers, 12 battleships and one coast-defense vessel. The total was larger than any during the past five years. The total tonnage was 305,362, the number of officers and men employed being 20,853 of the Royal Navy; in addition to which there were 535 men of the Royal Naval Reserve mobilized. The whole number of ships were divided, as usual, into two bodies, designated the Red and Blue fleets.
It is unnecessary to follow the bare description given of the details of operations. The operations took place mostly off the coast of Ireland. There was a forbidden belt. There was the usual amount of scouting, cruising and manoeuvring, and on August 5 the combined Blue Fleet, composed of 22 ships, were sighted on the port bow of the B Red Fleet, consisting of 15 ships. The Blues manoeuvred to prevent the Reds from getting into Belfast, and an engagement which lasted about 50 minutes took place. The Red ships got into Belfast Lough, but in doing so they passed within six cables of the Maidens, and thus broke one of the rules, the penalty being that they were put out of action by the umpire for 24 hours. After this the Blue Fleet stood to the southward to look for the remainder of the Red Fleet, which was discovered. An engagement began, and the part of the Red Fleet which had been ruled out of action followed and took part in the fight. As, however, the Red ships out of action should not have been present, the victory was therefore given to the Blues, who were outnumbered to the required extent. This must have been an unpleasant surprise to the Admiral of the conquered fleet, who was not aware that his auxiliaries were officially nonexistent, although very palpably present in actual force.
No ship was put out of action by a torpedo-boat, a fact to be chiefly attributed to the lightness of the nights. One of the Red torpedo-boats, however, had apparently a chance which she failed to take advantage of, supposing her enemy to be one of the group exempted from torpedo attack by the rules. This incident, as well as that of the Red ships being out of action, and yet able to take part in the fight, shows the, difficulty of bringing make-believe warfare to the likeness of the real thing.
The Red torpedo-boat referred to, which failed to attack her opponent through a misconception of her character, had been driven off by a "catcher "—we thought the term was tabooed in naval circles—and at first missed the Blue Fleet, but managed to keep up with it and got within range of the rear ship, which, as stated, she did not attack. The lieutenant in command states that, owing to the speed of the hostile fleet, the boats were unable to regain their position for attack when once it had been lost. "From this it seems permissible to infer," says the report, "that high speed will be of itself no unimportant protection to ships traversing at night narrow waters infested by torpedo-boats"; a proposition which we should have thought a self-evident fact.
The torpedo-boat operations are described as having been upon a too restricted scale to supply much valuable instruction, a remark which applies equally as well to the report itself. So far as the operations went, however, they tend to confirm the view that the most effective employment of the torpedo-boat in war will be limited to sending her to attack an enemy's ship in a known position within the boat's range of action. The necessity of combining with torpedo-boats vessels of a larger class to discover the enemy is also insisted upon. A mere flotilla of torpedo-boats is therefore considered "as a belligerent factor of distinctly imperfect efficiency." It is surprising how much attention the torpedo-boats always seem to occupy in these manoeuvres, and yet we are always being told they are little or no good.
TEST OF THE PNEUMATIC GUNS.
[AMERICAN ENGINEER AND RAILROAD JOURNAL.]
In our issue for September, 1894, we illustrated and described the pneumatic dynamite guns that have been placed at Sandy Hook for the protection of the channels entering New York harbor. Our readers will remember that this battery consists of one 8-in, and two 15-in, guns, built by the Pneumatic Torpedo and Construction Company. For the details of the arrangement and construction of the battery we refer to our previous article.
As the guns were built under a contract with the government, wherein the latter assumed no responsibility except to pay for the guns, provided they fulfilled the requirements of the agreement, it was of the utmost importance that the performance of the guns should be such that the most exacting board could find nothing to criticise. The testing of these guns had been carried on for some time under the auspices of the company's officers, and an elaborate system of records preserved showing the fall in pressure in the air cylinders for various air and service charges, the former corresponding to blank cartridges in the ordinary rifle. After a long series of such trials, in which the setting of the valve was carefully observed for ranges and action, the official acceptance test was made.
The endurance test of the whole plant was, as given in our previous account, 50 rounds in the first hour, 20 being from the 8-in, gun and 15 from each of the two 15-in.; then, for the next two hours, 30 rounds per hour. These were merely "air shots," but the valve was set for extreme range. The results of this excessive trial, that far exceeded anything the battery could ever be called upon to meet in service, were that 50 shots were fired in the first hour, 33 in the second and 36 in the third. The initial air pressure at the firing of the first shot was 1008 lbs. per square inch, and though this was not exceeded at any time during the trial, it was touched at several times during the second and third hours. The lowest point touched by the pressure was 930 lbs., at which the sixth shot in the third hour was fired. It may be roughly stated that a firing pressure of 1000 lbs. was maintained throughout, and no shot, with the single exception of the one mentioned, was fired at less than 990 lbs.
We have mentioned this endurance test first because it depended upon the machinery of the steam plant for its execution, although it was the last on the list.
The development of the pneumatic gun—for it has been a case of development—started with the fundamental idea of throwing a charge of dynamite with compressed air; and it having been demonstrated that this could be done, it became necessary to so control the admission of the air that the shot could be fired accurately, for it would be of little use in hurling dynamite about unless there is some probability of its striking the object at which it is aimed, and at this point the development of the gun came in as exemplified by the wonderful valve designed by Captain Rapieff.
It is useless to deny that the original guns were inaccurate, but this does not hold good of the present battery at Sandy Hook. Through the courtesy of the company we are enabled to give diagrams of the targets of three sets of these shots. The striking point of the shots was located by means of plane tables. For the shorter ranges there were two observers stationed on either side of the battery, at distances of 596 yds. to the right and 627 yds. to the left; while, for the longer ranges, there was a third observer on the Romer Shoals beacon, which stood off from the line of firing at an angle of 17° 19' and a distance of 5150 yds.
It would be uninteresting to our readers to recapitulate the results obtained by each shot, and we therefore confine ourselves to the sets that are here plotted. In Fig. 4 it will be observed that there is a plotting of the zones of danger to a first-class armored vessel due to the explosion of 500 lbs., 200 lbs. and 100 lbs. of high explosive respectively, as plotted from the formula of General Abbot. The plotting of the three sets of shots is done on this same scale.
Referring to Fig. 1, which represents the plotting of five shots fired from the 15-in, gun with 500 lbs. of explosive in each shot. The specification required that 74 per cent. of these shots should fall within the area of a rectangle 120 yds. long and 30 yds. wide. As a matter of fact, the whole five fell within a rectangle 41 yds. long and 10 yds. wide, while four out of the five fell on the line of flee. Fig. 2 is the similar plotting, eight shots containing 200 lbs. of explosive that fell within a rectangle 42 yds. long and 5 yds. wide, whereas the specifications only required that 54 1/2 per cent. should fall within a rectangle 120 yds. long and 30 yds. wide. This Fig. 2 represents the extreme contract range, and the figures appended to the striking point of each shot indicate the distance from the battery at which it struck the water. Fig. 3 is a similar plotting of shots containing 100 lbs. of explosive fired from the 8-in, gun, and shows that the five shots fell within a rectangle of 57 yds. long and 3 ¾ yds. wide, while the specification target was 120 yds. long and 30 yds. wide, with 66 per cent. hits required. We may therefore safely conclude that the accuracy of fire of these guns stands at a high point.
In our September issue we stated that these guns "command the whole southern approach to New York harbor." An actual plotting of the ranges shows that the 15-in, guns can throw 200-lb. charges to any point along the main channel for a distance of about 9000 yds., and for 4200 yds. through the awash channel. If a vessel were to enter the harbor at a speed of 20 miles per hour, it would, therefore, be exposed to the fire of the 15-in, guns with 200-lb. charges for 16 minutes if it were running the main channel and 7 ½ minutes if it were in the swash channel. In the first case the two guns could throw 20 projectiles, and in the latter 10 projectiles. Further, the guns are capable of throwing 500-lb. projectiles to any point for a distance of 4300 yds. along the main channel, and could fire eight projectiles at a vessel running 20 miles an hour before it was out of range, but could not reach the swash channel. This rate of firing cannot even be approached by the rifled guns, while there is nothing in the shape of a torpedo-thrower that can possibly be compared with this performance.
The acceptance tests also included an examination into the time required for the mechanical operation of the guns, such as elevating, depressing, and traversing. The guns can be operated by hand or by electric motors. The latter will carry them through 360° in 48% seconds for the 15-in, guns, and 1 minute 25% seconds for the 8-in, guns, while the same work can be done by hand in 8 minutes 11 seconds and 5 minutes 56 seconds respectively. The electric motor will elevate the 8-in, gun from 0° to 35° in 14 seconds and depress it in 15 seconds; the elevation and depression of the 15-in, gun to 34 ½” in 8 ½ seconds and 9 ½ seconds; hand power requiring 45 seconds and 48 seconds for the 8-in. and 26 ½ seconds and 26 seconds respectively.
One of the prime elements in the success of a dynamite gun is to have a suitable fuze. In regard to this we can only say at this time that out of all the shots fired—and there were 38 official and 8 extra for the company's exhibition—only two failed to explode on impact, and some were fired at the close range of 100 yds. In a future issue we will illustrate this fuze and then give a further account of its action in these tests.
The trials demonstrated that this battery has exceeded the demands of the specifications in almost every particular, and it has therefore been accepted by the government. The company are now at work upon the battery that is to be located in the harbor of San Francisco, thus giving to the main Atlantic and Pacific harbors of the United States the most efficient type of torpedo-throwing battery.
LEGAL ELECTRICAL UNITS IN THE UNITED STATES.
The units of electrical measure recommended by the International Electrical Congress, held at Chicago in 1893, were officially adopted by the U. S. Office of Standard Weights and Measures, with the approval of the Secretary of the Treasury. While this action affected all government contracts in which electrical measures were involved, it was in no way binding upon state, municipal or private operations. To remedy this deficiency, the law given below was passed by both houses of Congress and signed by the President, and became a law on July 12, 1894. It supersedes all previous action in the matter, and substantially agrees with the recommendations of the International Congress. The specifications referred to in Section 2 have not yet been prepared by the National Academy of Sciences, but are expected shortly:
AN ACT TO DEFINE AND ESTABLISH THE UNITS OF ELECTRICAL MEASURE.
From and after the passage of this act the legal units of electric measure in the United States shall be as follows: (1) The unit of resistance shall be what is known as the international ohm, which is substantially equal to 1,000,000,000 units of resistance of the centimetergram- second system of electro-magnetic units, and is represented by the resistance offered to an unvarying electric current by a column of mercury at the temperature of melting ice, 14.4521 grams in mass, of a constant cross-sectional area, and of the length of 106.3 cm.
(2) The unit of current shall be what is known as the international ampere, which is one-tenth of the unit of current of the centimetergram- second system of electro-magnetic units, and is the practical equivalent of the unvarying current, which, when passed through a solution of nitrate of silver in water in accordance with standard specifications, deposits silver at the rate of 0.001118 gram per second.
(3) The unit of electromotive force shall be what is known as the international volt, which is the electromotive force that, steadily applied to a conductor whose resistance is one international ohm, will produce a current of an international ampere, and is practically equivalent to of the electromotive force between the poles or 1434 electrodes of the voltaic cell known as Clark's cell, at a temperature of 15° C., and prepared in the manner described in the standard specifications.
(4) The unit of quantity shall be what is known as the international coulomb, which is the quantity of electricity transferred by a current of one international ampere in one second.
(5) The unit of capacity shall be what is known as the international farad, which is the capacity of a condenser charged to a potential of one international volt by one international coulomb of electricity.
(6) The unit of work shall be the joule, which is equal to ten million units of work in the centimeter-gram-second system, and which is practically equivalent to the energy expended in one second by an international ampere in an international ohm.
(7) The unit of power shall be the watt, which is equal to ten million units of power in the centimeter-gram-second system, and which is practically equivalent to, the work done at the rate of one joule per second.
(8) The unit of induction shall be the henry, which is the induction in a circuit when the electromotive force induced in this circuit is one international volt while the inducing current varies at the rate of one ampere per second.
Sec. 2. That it shall be the duty of the National Academy of Sciences to prescribe and publish, as soon as possible after the passage of this act, such specifications of details as shall be necessary for the practical application of the definitions of the ampere and volt hereinbefore given, and such specifications shall be the standard specifications herein mentioned.
SHIPS OF WAR.
[ENGLAND.]
THE MAGNIFICENT AND MAJESTIC.
The Magnificent was successfully floated out of dock on December 19 and the Majestic on January 31. These two vessels form part of a fleet of seven of precisely similar character already under construction or laid down. When completed they will be, in point of weight of broadside and end-on fire, as well as in respect of armored protection, the most modern and formidable engines of war as yet seen afloat. For, although the main armament in the barbettes consists of 12-in. 50-ton guns, instead of the huge 70-ton weapons of the Royal Sovereign and Hood, the extra rapidity with which these lighter and more manageable pieces of ordnance can be worked, and the tremendous preponderance of large caliber quick-firers which can be discharged six and seven times per minute, render the weight of metal thrown in a given interval of time far greater in the two vessels now under consideration. Similarly, although the actual thickness of armor-plating upon the sides and barbettes has been lessened, its capacity for resistance has been increased fifty per cent. by Harveyizing it, and the extent of armored surface has been enormously developed. The superficial armored area of the Magnificent's great citadel is, independently of the barbettes, nearly 9000 ft.
The principal dimensions, etc., of the two new battle-ships are as follows: Length, between perpendiculars, 390 ft., or 415 ft. over all; beam, 75 ft. at the water-line; mean draught of water, 271/2ft.; displacement, 14,900 tons; indicated horse power, 12,000; speed, under natural draught, 16 ½ knots, under moderate forced draught 171/2knots; of coal capacity there is a total storage of 1800 tons, but only 900 tons of this can be carried at the designed draught.
The disposition of the armored protection is quite different from that of the Royal Sovereign class. Instead of a narrow strip of thick armor at the water-line, surmounted by another strip of very thin armor, the upper edge of which is 91/2ft. above the water-line, there is a broad streak of Harveyed steel 151/2ft. wide, stretching from apex to apex of a pointed citadel. This is 9 in. thick upon the broadsides and 14 in. thick around the barbettes, where it merges into bulkheads. Within this armored citadel is the thickest portion of the armored deck, where it is 3 in. on the flat and 4 in. upon the curved sloping edges. Forward and aft, beyond the armored bulkheads, the armored deck is 21/2 in. thick at its stoutest part. But an important modification has been made in the armored deck. In all earlier battle-ships the outer edge of this deck is at the summit of the thick armor belt. In the Magnificent and Majestic, however, it curves downwards behind the vertical armor, and the lower edges of the two harmonize, as well as the outer edges of the forward and after armored decks, thus bringing the whole to a uniform level of about 5 ft. or 6 ft. below the water-line. The protective deck is, therefore, of a truly turtle-back character, as first of all developed so prominently in the design of the Vulcan. The barbettes are built upon the citadel ends of the armored deck and are to be plated with 14 in. Harveyed steel. Upon their summits will be revolving armored hoods of sufficient capacity to hold the gun detachments working the guns by manual power, and as the barbettes are pear-shaped in plan, there will be room within the thin ends for the ordinary ammunition hoists and ramming gear required for fixed loading positions. There is, however, an axial ammunition trunk within the barbettes, which descends to the magazines direct, to which we shall advert presently. Another feature for the protection of the water-line is the filling in with water-tight divisions of the angular space between the curved edges of the armored deck and the lower streak of armor belting, thus forming a sort of cofferdam around the vessel at this level. A similar contrivance has been designed for some of the war vessels of France now under construction.
The secondary armament, consisting of 6-in, quick-firers, is all protected by 6-in, armor on the outside of the casemates and 2-in, plates on their other side. A valuable modification has been made in the arrangement of the upper deck battery. Instead of an open space, liable to be swept by the machine and quick-firing guns of the enemy, both from the armored tops and otherwise, this is now enclosed and decked over with a steel shelter deck, the four armored casemates at either corner acting moreover as screens to prevent a raking fire from either quarter. There is also beneath the forward bridge a flying deck, upon which light quick-firing guns will be placed. Above this towers the chart-room, rising to an altitude of 75 ft. from the under side of the keel. It is impossible to conceive anything more important to the steadiness and discipline of the guns' crews than the fact of their being able to fight their weapons behind adequate shelter, and this question has been thoroughly solved in the upper works of the Magnificent and Majestic.
The armament of these vessels and its disposition is as follows: Two 12-in. wire 50-ton guns are to be mounted upon each barbette, protected by a steel revolving hood, as in the case of the Barfleur and Renown. Beneath the turntables will be a revolving shell chamber, with an ammunition trunk in the center and hoists, so that loading can be carried out with the guns at any position of training. This is independent of the fixed loading positions, whose hoists are in the pear-shaped ends of the barbettes. Thus the rapidity of fire and of the serving of the ammunition are accentuated considerably by this twofold arrangement, not to speak of the value of an alternative system in the event of one having been placed hors de combat by accident. It will be observed that whilst the freeboard of the new vessels has been raised to a height of more than 20 ft. forward, the axis of the heavy guns has been also raised to 27 ft. above the water-line, being 4 ft. higher than in the case of the Royal Sovereign class. This will admit of the guns being fired axially forward or aft, without endangering the safety of the deck, an impossibility in the earlier vessels. Upon the main deck are eight 6-in, quick-firers in armored casemates, four on either broadside, and four more of these guns are upon the upper deck battery, one in an armored casemate at each corner, as will be seen in the engraving. The part of the shelter deck above these last-mentioned corner casemates is double plated to give additional strength. In the upper deck battery will be also twelve 12-pounder quick-firers upon shielded mountings, six on either broadside, and the remaining four 12- pounders will be forward and aft upon the superstructure. The two forward ones will be under the flying deck. Twelve 3-pounder quickfirers will be disposed upon the superstructure, tops, and in other situations. Eight machine guns will also be carried, and five torpedo tubes or dischargers. Two 12-in, guns, two 6-in, quick-firers, two 12-pounder, and seven or five 3-pounder quick-firers can be directed simultaneously either ahead or astern, whilst the broadside fired on either beam would be delivered from four 12-in., six 6-in, quick-firers, eight 12-pounder and eight 3-pounder quick-firers. In four minutes a weight of 30,000 lbs. of metal would thus be discharged from one broadside, whilst the corresponding figure forward or aft would be about 12,000 lbs. It must be borne in mind that all this concentration of fire has not been obtained, as in the case of the French battle-ships of the Charlemagne class, by fitting the guns into lateral grooves like the blades of a pocket knife, which must inevitably sacrifice the stability of the ship when axial fire is employed, but that each gun has a clear arc for itself without interfering with any adjacent works or with the rest of the armament.
The propelling machinery of the new vessels consists of two sets of engines of the ordinary inverted triple-expansion compound condensing type, the cylinders being 40 in., 59 in., and 88 in. in diameter respectively, by 51 in. stroke. The twin propellers are of gun-metal, and are 17 ft. in diameter and of 19 ft. 9 in. pitch. The boilers are eight in number, and are of the ordinary marine type, being 16 ft. 1 in. in diameter and 9 ft. 3 in. long, each containing four furnaces. They weigh about 50 tons each. The working pressure will be 150 lbs. per square inch. The main steam pipes will be of steel. The chief novelty in this connection is the application of induced instead of forced draught. The makers of the Magnificent's engines are Messrs. John Penn & Sons; those of the Majestic will be made at Barrow.
The two new battle-ships, although very fine in their lines forward and aft, are tolerably square at the midship section, the result being that their coefficient of fineness below the water-line area is .65 of a solid rectangle contained by the length, beam and draught.
The Magnificent was only laid down upon the 18th of December, 1893, and the Majestic upon the 5th of February, 1894; hence their readiness for floating out in so short a space of time is almost phenomenal.
Ammunition is supplied, save to the 12-pounder gun positions, through passages and trunks which are all either constructed of armor or are under protection. Beneath each gun position is an independent armored trunk, so that accidents from shells bursting between decks would be minimized in number and effects. The new ships will be fitted with two masts, with two fighting tops upon each. Each top will carry three 3-pounder quick-fire guns, with the necessary magazines and equipments. The mainmast will be fitted with a steel derrick 56 ft. long, for lifting the heavy boats into their positions on the skid beams over the upper deck. Each mast will also carry on a platform at its head a powerful electric light for signaling and searching purposes. The complement of boats is eighteen, four of which are steamboats, and will be capable of acting independently of the ship for purposes of torpedo attack, and four of the lighter boats will be carried on davits of special construction, which will enable them to be lowered at a moment's notice. The main and auxiliary condensers are formed of brass throughout, and possess a cooling surface of 13,500 square feet and 1800 square feet respectively.
In a comparison with the Charlemagne, the first feature that strikes one is that displacement and indicated horse power are nearly reversed as to their relative proportions; but, of course, the extra-engine power of the French vessel is mainly required for the third propeller, and we cannot admit that the result of experiments with triple-screw vessels Is so satisfactory as to cause us a feeling of regret that more powerful engines have not been designed for the Magnificent class. At the same time if 18 or 18 1/2 knots is got out of the Charlemagne by applying all her screw power, it will give her manoeuvring qualities superior to those of the British battle-ships. This remains, however, to be proved.
The double-armored decks of the Charlemagne are a valuable modification, and the cofferdam between them may prove to be a most useful adjunct to the water-tight qualities of the ship; but it seems to us that, If the stability of the vessel was not disturbed by the arrangement, the two decks would have been more effective combined in one thickness. The turtle-back deck of the Magnificent, stretching from bow to stern, and reaching down far over the sides amidships, with its four inches of steel, is superior, we believe, to the French cofferdam.
The method by which axial fire ahead and astern has been secured appears so likely to be detrimental to the safety of the vessel's upper works when the guns are trained directly fore and aft, that we cannot recommend it. But the plan of securing the upper deck battery of 5 1/2-in. guns behind a complete belt of 3-in, armor cannot be too highly approved. The conning towers are also well placed and at a commanding altitude, though it is a little difficult to understand what security is afforded to the officers in the forward one, in the event of the mast being shot away upon which it is perched, the latter not being armored.
The power of the armament mounted upon the Magnificent is incomparably superior to that of the French vessel. The twelve 6-in, quickfirers upon the former, each with its isolated casemate protected by 6-in. steel, and the sixteen 12-pounder quick-firers of the new Elswick pattern, compose an auxiliary armament so tremendous in its potency that no moderate-sized cruiser could live in the vicinity of the battleship, even if keeping under weigh at a rapid rate of steaming, so as to avoid the fire of the main armament of 12-in, heavy guns. The uniform height, 27 ft., of the British heavy guns above the water-line is also a distinct advantage.
The total coal capacity, and consequent radius of action of the British battle-ship, is considerably greater than that of the Charlemagne. Eighteen hundred tons of coal can, in emergency, be stowed away in the former, but the extreme capacity of the latter is only 1100. This is an important characteristic for long sea voyages.
THE TORPEDO-BOAT DESTROYER BRUIZER.
On March 28, in boisterous weather, a full-speed official trial was run of the last of the torpedo-boat destroyers which Messrs. Thornycroft & Co. have built for the Admiralty. The trial was not notable on account of the speed attained, but that is simply on account of the high standard which the builders themselves have raised for these remarkable craft. A short time ago 28 knots, which the Bruizer all but attained on her three hours' run, would have been looked upon as phenomenal; but it has been exceeded by about a knot in the sister vessel, the Boxer, also constructed at the Chiswick yard.
The Bruizer is 201 ft. 6 in. long and 19 ft. wide; she is 13 ft. deep, and her maximum draught is 7 ft. 4 in. at trial draught. The displacement of the vessels of this class is about 220 tons. The engines are similar to those of the Daring. These engines are of quite novel design, and now the trials of the five destroyers in which they have been fitted are complete, it is satisfactory, to learn that the engines have given no trouble throughout. The same may be said of the water-tube boilers which have been fitted in these vessels. There have been run, in all, 23 fullspeed trials of these vessels, and there has not been an accident or mishap through the failure of the boilers throughout. The fact is of interest in view of the controversy now going on on the subject of watertube boilers. The enormous test that the machinery of these high-speed craft is put to on full-speed trials must be remembered in connection with this subject. The Bruizer has three Thornycroft boilers placed in two stokeholds. A modified design of Daring boiler is used, the arrangement being the same as that adopted in the Ardent, by which an addition to the heating surface is obtained by a somewhat different disposition of the tubes in the rows next to the casing. The Daring had 8892 square feet of heating surface and 189 square feet of grate surface. The engines of all these vessels are of the three-stage compound type, each set having high-pressure cylinders 19 in. in diameter, intermediate cylinders 27 in. in diameter, and two low-pressure cylinders each of 27 in. diameter. The stroke is 16 in.
In the Speedy a new device was tried for controlling the distribution of the feed in the water-tube boilers with which that vessel was fitted. It is this question of feed distribution which was so long the rock ahead for the water-tubists when an attempt was made to run these boilers in groups. It was argued, not without reason, that in steam generators of this sensitive nature, and with so small a water-holding capacity, unless the feed were very evenly distributed, disaster would follow. In order to avoid this various devices have been tried, with more or less success. That introduced by Messrs. Thornycroft consists of a hollow steel float, capable of withstanding the boiler pressure, which is placed Inside the separator or steam-connecting cylinder which forms so important a feature in the Thornycroft boiler. By a system of levers, somewhat too complicated to describe without the aid of diagrams, the float regulates the opening of a check valve which is placed within the boiler, the amount the valve is opened determining the volume of feed. In this way the water-level in the boiler determines the amount of feed admitted; thus, if the water level falls, the check valve is thrown wider open; if it rise the check valve is closed. Unlike most gears of the kind, the motion of the float has not to be conveyed to the exterior of the boiler through a stuffing box. An arrangement of the latter nature must lose much of its sensitiveness, and herein the Thornycroft gear has a manifest advantage. There is, however, in this device a means of regulating the normal water level by hand, and this is effected through a rod which passes outside the separator through a stuffing box and is worked by a hand wheel. In this way the gear may be set so that the water level can be carried at any required height. The gear has, we hear, been found in practice to act admirably, and we understand it is contemplated using it in some vessels built by other firms. On the occasion of the Bruizer's trial on March 28, the feed water between the three boilers was properly distributed by it, the report being that no hand adjustment was required throughout.
The Bruizer differs from the earlier vessels of this class in having solid manganese bronze propellers. It has long been the practice of the torpedo- boat builders to forge the propeller blades separately and key them Into a boss. This plan answered well so long as steel blades only were used, but when manganese bronze was required it was found there was danger of the blades getting loose in the boss. In order to avoid this, a new method of keying it was devised, but it is now thought desirable to have the propellers cast in one. The screws of the Bruizer are three-bladed, all surfaces being polished.
The furnace doors are fitted with springs so as to be self-closing, and the ash-pit doors being self-closing there is less danger to the stokers in case of a burst tube, as the steam would go up the chimney.
At the conclusion of the speed trials, circles were turned on both hands. The circle with helm to port was accomplished in 1 minute 46 seconds, with the helm to starboard in 1 minute 52 seconds. This was In a strong wind, the force being 5 to 6. The weather was too rough to make circles astern, so that part of the trial is reserved for another time.
THE BANSHEE AND CONTEST.
Her Majesty's ships Banshee and Contest, two of the torpedo-boat destroyers building for the British Government by Messrs. Laird Brothers, of Birkenhead, have completed their official trials on the measured mile on the Clyde, and the contractors have to be congratulated on highly satisfactory results. Messrs. Laird have availed to the fullest extent in designing the hulls and machinery of these vessels of their past experience with high-speed ships, with which they have had an unbroken line of successes, including her Majesty's ships Rattlesnake, Onyx, and Renard; the Almirante Lynch and Almirante Condell, for the Chilian navy; the Espora and Rosales, for the Argentine navy; and the machinery they fitted to her Majesty's ships Skipjack and Speedwell; and more particularly they have followed the information obtained in connection with her Majesty's ships Ferret and Lynx, the two torpedo-boat destroyers which they successfully tried and delivered in the summer of last year. The Banshee and Contest are 210 ft. long with 194 ft. beam, and generally similar in construction to the Ferret and Lynx, which we described in our issue of 7th September last. The armament, however, has been modified, and now consists of one 12- pounder and five 6-pounder quick-firing guns, two separate torpedo tubes on the deck, and no bow tube, and they are equipped with the latest type of 18-in. torpedoes. The engines are Messrs. Laird's wellknown tri-compound type, the cylinders being 19 in., 29 in., and 43 in. in diameter by 18 in. stroke, and it is worthy of notice that all parts of the engines are accessible when working at full speed, and all the starting and reversing gear, etc., is worked from a platform at the forward end of the engine-room. It has been a very satisfactory feature in the machinery of Messrs. Laird's make that they have designed their engines with cylinders large enough to give the required power at a reasonable number of revolutions, and on the trial of the Banshee the average for the three hours was only 345. The boilers are a modified form of the Normand type, and no difficulty was experienced throughout the three hours' trial in maintaining the steam at the intended pressure. There was no indication of priming either on the official or preliminary trials.
The official trial of the Banshee took place on Thursday, February 21st. The three hours' trial was commenced at eleven o'clock, the vessel having on board her full normal weight, and the average speed for the whole time was found to be 27.6 knots, or 31.8 miles per hour, with 345 revolutions. After the run the usual trials as to manceuvring were made. The helm was put from hard over to hard over both ways in less than ten seconds, each at full speed, and the steering both ahead and astern was proved to be entirely satisfactory. The trial of the Contest was made under similar conditions the following day, and the mean speed for the three hours was 27.4 knots, with 350 revolutions. There was a remarkable absence of vibration when running at full speed, and no hitch of any kind occurred in the machinery. The seagoing qualities of these boats are perhaps as interesting as the mere speed. An illustration of their success in this direction has been afforded by the Banshee and Contest. The first left Birkenhead under easy steam at 3 P. M. on Friday, February 14th, and reached Greenock at 3 o'clock next morning, in spite of a heavy southeast gale which prevaned from the Mull of Galloway onwards.
The Contest left Birkenhead on February 19th, at 7.15 A. M., and reached Greenock at 4.50 the same afternoon—over twenty knots average— and the vessels were got ready for trial and all the weights adjusted as recorded above. Messrs. Laird only received the order for these boats in February of last year, and the rapidity with which they have been brought forward for trial is highly creditable, and it showed great confidence in the machinery to make the trials of two such boats on successive days, especially as the Banshee had only been twice and the Contest only once under weigh before leaving the Mersey to make their trials. The third boat of the lot is named the Dragon, and is now ready for steam, and will be tried very shortly.
THE ROCKET AND SHARK.
While such high speeds as 28 knots were attained with these and the other vessels constructed by Messrs. James and George Thomson, Limited, Clydebank, on experimental runs, the firm, on the official trials which have just been concluded, contented themselves by just exceeding their guarantee. Thus, having ascertained that 396 revolutions per minute insured 27 knots under all conditions of weather and full displacement, they decided not to go far beyond this. The mean results of the six runs on the measured mile, three in each direction, may be thus tabulated:
MEANS OF SIX RUNS ON MEASURED MILE.
Rocket. Shark.
Date of trial Feb. 27. March 1.
Air pressure in stokehold 3.5 in. 3 in.
Steam pressure at boilers 188 lbs. 184 lbs.
Revolutions, port engine 399 400
Revolutions, starboard engine 397 397
Vacuum 25 in. 25 in.
Speed of boat 27.7 knots. 27.5 knots.
On the three hours' run in the Firth, with full weights on board, indicator diagrams were taken every quarter-hour, and the results were as follows, the speed being determined by the mean revolutions of the engines:
Rocket. Shark.
Revolutions of engines 396 401
Speed of boat 27.4 knots. 27.6 knots.
Indicated horse power 4200 4250
One feature of special note is the wave line. The Rocket and her consorts have an exceptionally fine entry, with a flat floor and little tumble home amidships. The stem is straight. In this respect she differs from some of the earlier craft, which had a torpedo-ejecting tube firing straight ahead; but it was found in practice that the impact of the torpedo on the water retarded it so much as to cause the destroyer, when steaming 27 knots, to overrun it. The later vessels, therefore, have only a double torpedo launching gun on deck, and the change has enabled greater accommodation to be provided for the crew, under the turtle-decked forecastle-head, where there will be mounted a 12-pounder quick-firing gun over the conning tower, with two 6-pounder guns on either side behind the shelter of the forecastle. The deadwood between the outboard propeller shafting is cut away, so as to afford a freer flow of water to the twin propellers, which are of manganese bronze. The rudder is of the usual type, supported on the usual pintle, the lesser depth being compensated for by greater width.
The machinery consists of two sets of triple-expansion engines. All the working parts are of forged steel and are balanced. The cylinders are supported on steel columns, thoroughly braced, the condenser being separated. The engines were run at a high speed in the erecting shop to ascertain the efficiency of the balancing, and the results on trial were satisfactory. The high-pressure cylinders are 18% ins, in diameter, the intermediate 26% in., and the low pressure 40% in., the stroke being 1 ft. 6 in. The piston speed on trial was therefore about 1200 ft. per minute.
There are four water-tube boilers of the Normand type, but it may be here stated that they have two water drums on either side, with the fire-grate between, and from these two drums there are tubes extending in curves of many forms to a central steam drum on the top, the tubes entering in the lower part of the steam receiver or below the water level. The tubes in the rows nearest the fire are of steel, the others are of copper. At the back of the grate the tubes are so curved as to partly close in the furnace end, and in addition the tubes are arranged to prevent the hot gases escaping before the greater portion of the heat has been absorbed. The outside walls consist of galvanized steel tubes. The boilers practically occupy the full size of the compartments, which are covered with a heat-resisting substance placed under the deck. The grate area is 163 square feet and the heating surface 8600 square feet, so that the power was equal to 26.07 indicated horse power per square foot of grate area and to 1 horse power per 2.02 square feet of heating surface. The two center boilers have a smokestack in common, while the forward and after boilers have separate funnels smaller than the center funnel. The engines are abaft the boiler compartments.
[SPAIN.]
THE EMPERADOR CARLOS V.
There was launched on March 12, at Cadiz, a first-class protected cruiser for the Spanish Navy.
The displacement of the vessel will be, in sea trim, 9089 tons, the length between perpendiculars being 380 ft., and over all 404 ft. 9 in., the beam 67 ft., and the draught 24 ft. forward, 26 ft. aft and 25 ft. mean. The hull has been built by Messrs. Yea Murgia and Co., Siemens-Martin steel being used, and there is side armor 2 in. thick, 1 in. of Siemens- Martin steel, and the other inch of chrome steel. The protective deck is of steel, the maximum thickness being 6% in., made up of three plates. The armament consists of two 28-centimeter Hontoria guns, eight 14- centimeter Hontoria quick-firing guns, four 10-centimeter and two 7- centimeter quick-firing guns, four 57-millimeter and four 37-millimeter Nordenfelt guns, two machine guns (mitrailleuse), and six Schwartzkopff torpedo tubes.
The twin engines are of the four-cylinder triple-expansion type, there being two 25-in, high-pressure cylinders, two 77 3-16-in, intermediate, and four 82 3-32-in, low-pressure cylinders, the piston stroke being 45 5-16-in. Steam at 147 lbs. pressure is supplied by 12 single-ended boilers, 16 ft. 3% in. in diameter by 9 ft. 10% in. long. Under natural draught the power to be developed is 15,000 indicated horse power, and under forced draught 18,500 indicated horse power, the speed being, under the former conditions 19 knots and under the latter 20 knots. The screw propellers, which are of bronze, have each four blades. The vessel has bunker capacity for 1771 tons, which gives her a radius of action of 13,000 sea miles at 10 knots. The machinery was constructed by the Maguinista Terrestre y Maritima, Barcelona. The cost of the vessel is about $3,400,000.