MARINE ENGINEERING IN THE RN

PART 11. 'THE SHIP IS A STEAM BEINGS

DAVID K. BROWN, MENG, CENG, FRINA, RCNC (Consult~lnt Naval At-chitect and Historiczn)

ABSTRACT The quotation in the title refers to the increasing use of auxiliarj, steam engines to work the guns.

pumps. ventilation, dynamos. etc. Early problems with the co~npound en,' olne were overcome, leading to a marked increase in efficiency and a reduction in the weight and space needed fol- machinery. Reliable steel. from the open hearth process, was introduced for both hull and machinery. Even higher pressures led to the triple expansion engine which was to power so lnany ships even after World War 11.

Compound Engines in Service Dreadi1ougl7t was originally laid down in 1870 as Fui-I., an enlarged Devas-

tation, but was redesigned by Barnaby and his assistant: White, following the 1872 Committee on Designs. The introduction of compound engines into the battle fleet was one of these changes, though Alexandt-a, described below, completed first, in 1877. Dreadnought's engines burned 50 tons 122 pounds during her six hour full power trial at 8216 ihp, which was equivalent to 2.27 lb/ ihphr.

FIG. I- 'ALEXANDRA', LAUNCHED 1875. THE FIRST LARGE SHIP WITH VERTICAL COMPOUND

ENGINES, OF 8500 ihp

Alexnndrn ( 1 875) (FIG. 1 ) was designed in the confused era following the loss of the Crrptain and the subsequent committee deliberations. She was a rigged,

centre battery ship and, as such, obsolescent at concept, though a fine example of the type. Her rig was wasted as she never made a voyage under sail.I6 Her twin shafts were driven by Humphrys and Tennant compound engines. l 7

Each engine had three cylinders arranged vertically above the crankshaft with a 90 inch LP cylinder either side of the 70 inch HP cylinder, all elaborately steam jacketed to avoid waste of heat. Early steam warships were forced to use horizontal engines so that they were protected by lying below the water line. This arrangement led to an awkward geometry with short connecting rods, causing vibration and rapid wear. Thick side armour-1 2 inches in Alexandm-made the simpler vertical engine acceptable though horizontal engines were used for many more years in unarmoured ships.

The engines were arranged on high seats to protect them from damage in grounding, an all too frequent occurrence in the 19th century navy. They were also braced to withstand the shock of ramming. Each crankshaft bearing brass had a large hole through the top so that a brave engineer could put his hand in and feel the temperature. Auxiliary engines were provided to turn the propellers at low speed while sailing, to reduce their drag.

The surface condenser had 16,500 sq ft of cooling surface with brass tubes 518 inch diameter, the centrifugal circulating pumps being driven by their own steam engine. If required, they could be used as simple jet condensers. There were 12 cylindrical boilers arranged in four spaces separated by a centre line and a transverse bulkhead; working pressure was 60 lb/in2 and the heating surface totalled 21,900 sq ft. The boilers were back to back against the longitudinal bulkhead so that the furnace doors were handy for the wing bunkers. Each boiler contained two hundredweight of zinc anodes which seem to have been effective since re-boilering was only needed after 16 years, a long life at that time.

Alexnndrn had an elaborate ventilation system with steam operated fans and, for the first time, bulkhead valves were fitted to prevent the spread of fire. The hollow iron lower masts, which were used as ventilation exhausts, were seen as a particular fire hazard as they could generate a very powerful updraught. The engine room complement consisted of a Chief Engineer, 10 Assistants and 80 stokers.

The armoured cruiser Nelson (1 874) had Elder compound engines designed by A. C. Kirk* who was responsible for many of the innovations of the day. Considerable attention was given to weight saving and, instead of the conven- tional heavy cast iron bedplate and columns, they had a braced structure with wrought iron bed and columns, somewhat similar to that used by Thornycroft for very light torpedo boat engines. The condenser shell was of plate brass and the end doors of wrought iron. These measures reduced weight by about 10%.ls

'The Ship is a Steam Being' The Inflexible (1876) (FIG. 2) had two three-cylinder compound engines by

Elder, very similar to those of Alexnndra just described. Steam was supplied by eight single and four double ended oval boilers. The crankshafts and inboard propeller shafts were of steel and were hollow. She had at least 39 auxiliary engines, and was described by E. J. Reed in a letter to the Times of 1 January 1877 as a:

. . . huge Engine of War, animated and put into activity in every part by steam and steam alone. The main propelling engines are worked by steam, a separate steam engine starts and stops them; steam ventilates the monster, steam weighs the anchors, steam steers her, steam pumps her out if she leaks, steam loads the gun, steam trains it. steam elevates or depresses it. The Ship is a steam being . . .

-p A C. K11-k made a m q o r contrihutlon to mat-lne engineering in the 10th century. For a fuller account of h ~ \ work see the recently puhlished 'Advent o l Stealn': Conway Meuatue Press. 1983: 'Triple expansion and the tir\t shipping revolut~on' . D Grifliths.

FIG. 2-'INFLEXIBLE', LAUNCHED 1876. SHE WAS FULL O F NOVELTIES A N D H A D N O L.ESS THAN 39 AUXILIARY ENGINES. HER MAIN ENGINES W E R E COMPOlJND O F 8400 ihp

Some early uses of steam were a capstan in Hercules (1866), a hydraulic steering gear in Warrior (1 870), and a steam steering engine for Northumberland, also in 1870. The numerous auxiliary engines of the Inflexible are listed below:

1 steering engine, horizontal direct acting (Forrester) 2 vertical direct acting fire engines 1 capstan engine 1 vertical direct turning engine 2 donkey engines fbr bilge pumping 4 auxiliary feed, similar to the donkey engines 4 Brotherhood 3 cylinder fan engines 2 horizontal direct acting centrifugal circulating pumps 2 reversing engines 2 pairs steadhydraulic engines for operating turrets (750 tons) 4 ash hoists 2 40 hp pumping engines (total pumping capacity, 4800 tonslhr) 2 steam shot hoists 2 Brotherhood 3 cylinder for boat hoisting 4 Friedman ejectors

An electric searchlight had been tried successfully in Comet in 1874 and the first permanent installation was in Minotaur in 1876. Her generator was AC, with 32 permanent magnets, worked at 400 revlmin by a belt off the pumping engine. During the following few years several battleships were fitted with dynamos and searchlights.

Injexible had 800 volts DC generators by the US Brush Company. These powered arc lights in the machinery spaces and Swan 'Glow' lamps elsewhere. The Swan lamps were connected in series between the bus bar and an arc lamp, an arrangement which only killed its first victim after a year in use. The introduction of torpedos required air compressors and the ADMIRAL Class in 1880 had a Brotherhood compressor which worked at 1000 lblsq in. Also in 1880 it was claimed that Sultan's fire pump. working at 100 lb/sq in, could throw a jet over her 200 ft mast and deliver 1120 gallonslminute.

Weapon Engineering De\~astation (1 869) was the first battleship without sails but her engines were

of the almost immortal Penn trunk design. Her sister, Thunderer, had Humphrys and Tennant direct acting engines. The latter ship was notable for the hydraulic operation, using a system devised by Rendel of Armstrongs, of her forward gun turret which mounted two 38 ton, 12 inch. muzzle loading rifles. Recoil was absorbed in a hydraulic ram with a spring loaded return valve: the same ram was used to run out the gun to fire. A hydraulic jack was used to elevate the gun, the effective pivoting point being arranged near the muzzle to permit a smaller gun port. The turret, which was 31 '5'4 feet in diameter and weighed 406 tons was carried on rollers. A steam engine below the turret drove a pinion engaging with a rack on the turret for training.

To load, the muzzles were depressed below the deck where the charge and shell were lifted and rammed hydraulically. In case of accident during loading, the guns pointed well above the waterline. The crew consisted of one officer in the turret. one operator below, together with eight others wheeling shells and charges to the loading position. a total of l 0 compared with 22 in her after turret. It was claimed that a prototype mounting on shore could fire one round every 45 seconds.

Ternernire (1 876) (FIG. 3) had a very different system for operating two of her I 1 inch, 25 ton guns. Fore and aft, there was an armoured pit on the upper deck in which a gun was loaded by a hydraulic ram. To fire, the gun would be raised over the lip of this pit by another hydraulic mechanism, the gun taking up a preset training angle as it rose. Elevation was set manually. The gun would only be exposed for a few seconds while firing and would then be lowered into the pit for reloading.

F I ~ ; . 3-'TFIMERAIRE' WAS I.AIINCI4ED IN 1876. SlHt: W A S NOTAB1.E F O R HItR HYDRAULICALI-Y

OI>ERAI.EI> 'I>ISAI)I>EARING' MOIJNTINGS FOR TWO OF H E R I I I N C I ~ MUZZL~I: I.OADEI> RIFLE13 GUNS. SI1OWN HERE. SHE W A S AI-SO T l l E BIGGEST B R I G EVER BUILT

The full crew was six, though it could be worked by three men if required. This compares with a crew of 19 for a similar gun on a manual, broadside mounting. At the bombardment of Alexandria, the accuracy of her fire was commended, but each single mount weighed as much as a twin turret. Tenzercrire was among the first to carry torpedos for her boats and she also had launchers for torpedos and four 20 pounder anti-torpedo boat guns with searchlights to find the attacker.

Steam Boats Steam boats had appeared in the 1850s and the first satisfactory design was

supplied by J . S. White in 1861 as a survey launch for Sylvi~r . It was a 27 ft boat with a speed of 9 knots. In 1864 White began to work with Bellis on a high speed engine for ships' boats which led to the Bellis and Morcom double-acting, enclosed, forced lubrication engine. A 36 ft design was introduced as an alternative to the heavy 40 ft boat with a two-cylinder, vertical, simple, non- condensing engine and loco~notive boiler. The machinery weight of the new unit was 4 tons and ~t burned 6 lb/ihp/hr. By the 1870s the bigger launches were fitted with either the spar torpedo or the Whitehead automobile torpedo. An advanced 42 ft pinnacle-known as the ' turnabo~~t ' boat-was built by White for Irzfip.\-- ihle, later developed into the 56 ft boat with a speed of 15 knots from 150 ihp for a machinery weight of 65'2 tons.

Before leaving the subject of boats, i t should be mentioned that, at the turn of the century, steam turbines were tried as boat engines but were unsatistictory as they could not be matched to a large slow running propeller.

'Iris'-Steel The despatch vessel Iris ( 1 877) (Frc;. 4), later reclassified as a 2nd class cruiser,

and her sister Mercur:~, ( 1 876) were extremely innovative ships and may be seen as the ancestor of the modern cruiser.I9 They were the first RN ships with steel hulls, made by the open hearth (Siemans-Martin) process at Landore in South

FIG. 4--'IRIS', T H E FASTEST S H I P IN T H E W O R L D WHEN L A U N C H E D IN 1877, FINALLY ACHIEVING 18.6 KNOTS. SHE WAS THE FIRST RN S H I P BUILT OF STEEL

Wales. The Admiralty thought that earlier steel produced by the Bessemer process was too inconsistent in its properties for use in warships. They were exceptionally fast ships for their day, reaching 18% knots on trial.

F I G . 5-A V I E W OF 'IRIS'S E N G I N E ROOMS, EACH WITH A MAUDSLAY C O M P O L I N D ENCiINI: 1)EVEI.OPING 3000 ihp

The two, 3500 ihp, 4 cylinder, Maudslay compound engines (FIG. 5 ) had the 41 inch HP cylinders in line with the 75 inch LP cylinders, with a stroke of 2 ft 9 inch. The two engines were in separate rooms divided by a transverse bulkhead, the forward engine driving the starboard shaft. There were also two boiler rooms, the machinery all together occupying half the 300 feet length of the ships. The coal bunkers were outboard of the machinery to provide protection and with four machinery spaces, well cross-connected, these two ships were quite resistant to damage.

The propeller shafts, inboard, were of Whitworth 'fluid compressed steel', 17 inch external diameter. As with all twin screw ships of the day, the shaft external to the hull (16% inch wrought iron) ran inside a gunmetal tube and the shaft itself had a gunmetal casing. The bearings were of lignum vitae.

The 12 boilers, 8 oval (FIG. 6 ) and 4 cylindrical, worked at 60 Ib/in2 with a total grate a]-ea of 69 sq ft and a heating surface of 15.900 sq ft and. for the first time, were constructed of steel. Steel had been used by the Admiralty for boiler shells from 1870 but, in this ship, the use of steel was extended to combustion chambers, furnaces and tube plates. Steel boilers weighed about 10% less than those of iron. Iris carried 500 tons of coal which gave her an endurance of 6200 miles at 10 knots and 2000 at full speed.

Sennett read a paper to the Institution of Naval Architects in 1888'0 in which he pointed out that the rules of Lloyds and the Board of Trade required a test pressure for boilers of double the working pressure which, when combined with a factor of safety of four, would lead to a test pressure would be half the ultimate and nearly equal to the elastic limit of steel. He had introduced new regulations for Admiralty boilers which required that the test pressure should not exceed 419 of

the ultimate and that the test pressure should be 90 lb/in2 greater than the working pressure.

Sennett used the boilers of the cruiser Medea as an example. The working pressure was to be 155 lb/in' so the test pressure was 245, which with a factor of safety of 2%, led to a wall thickness of 29/32 inch. Lloyds would require 1 5/32 inch and would limit working pressure to 123 while the Board of Trade rules gave 1% in and permit 1 10 lb/in2. In general, the Admiralty rules would give an 18% saving in weight and the boilers were perfectly satisfactory in service. Discussion of the paper was heated, each party accusing the others of dangerous practice.

Steel construction facilitated the use of the col-rugated furnace, introduced by Fox in 1874, and coming into general use about 188 1. The corrugations provided stiffening in the radial direction, increased the heating surface and took up longitudinal expansion. Brass boiler tubes remained in use until about 1882 when they were replaced by iron and later by lap welded steel.

Speed Trials Trials had been carried out since the introduction of the steam ship to ensure

that the machinery worked under load and to determine the ship's speed. In the early days, cheating was common, mostly by arranging that there were more runs with the tidal current than against it." Well before 1860, Admiralty rules for the conduct of trials had eliminated most cheating, though the contractors carrying out the trial were permitted to go to quite extreme lengths to obtain the best results, with extra stokers, chosen for their physique and skill, shovelling coal which had been sieved to obtain the optimuin size for combustion.

Speed trials of new ships, run in optimum conditions, demonstrated speeds considerably higher than those which could be reached in service; Reed and others putting the difference at about 1 f i knots. Understandably, many criticized the whole idea of formal, measured mile trials and proposed that they be replaced by a lengthy run at sea in normal operating conditions. The counter argument, which the Admiralty accepted, was that trial results, with everything at its best, were comparative between classes and hence were most useful since, until the mid 1870s. the only way to estimate the speed of a new design was by con~parison

with the trial results of a previous similar ship. The overload on the machinery imposed by the measured mile runs was valuable as a proof test and a six hour full power run was always part of the programme.

The trials of Iris, December 1877-August 1878, showed a number of problems with the propellers and the solutions contributed to much improved correlation between model tests and ship trials." On her first trial she was only able to reach 16.4 knots instead of the 17.5 confidently expected as a result of Froude's model tests. The propellers were four bladed with a disk area ratio of 0.3 (area of blade/ area swept by propeller disk).

A series of progressive speed trials, at various powers, as proposed by William Denny in his paper of 1875," were then run over a measured mile in February 1878. Two blades were then removed from each propeller and the trial repeated. The strength of the remaining blades was not thought adequate to run at full power but at powers up to just over half power, the two bladed screw was much more efficient which, at the time was attributed to reduced blade area. As it was believed that four-bladed screws were less likely to cause serious vibration, a new set was made with less diameter, increased pitch and significantly less blade area. These were tried in July, a pace which could not be matched today, when a speed of 18.6 knots was recorded. A new two-bladed set was tried at the beginning of August and, though the speed was increased by 0.014 knots, vibration was severe at some speeds and the four-bladed set was adopted for service.

Barnaby6 has shown, using modern propeller data, that the results of these trials are consistent and that the initial poor performance was due to an overlarge diameter and insufficient pitch and not to blade area. The effects of these were exaggerated as Iris was operating at a speedllength ratio close to unity where a comparatively small change in efficiency leads to appreciable changes in speed.

A number of important studies were carried out as part of the analysis of these trials. The engines were run with the shafts disconnected, and at 90 rev/min (full speed) it was tound that friction inside the engine absorbed about 400 ihp and i t was deduced that friction in the shafting absorbed another 170 ihp. Studies were made on the effect of the surface finish of the blade on their frictional drag. It was suggested, not altogether convincingly as contemporary knowledge was insuffi- cient to tackle what is a very difficult problem, that friction over the original propeller absorbed 1 120 ihp at full speed whilst the successful third set took only 420.

Froude carried out large-scale experiments in the tank at Torquay on the drag of shaft brackets and the exposed length of shafts, devising formulae for their drag which remained in use until well after World War 11. Progressive speed trials, following Denny's procedure, were of proven value and Froude devised empiri- cal 'Trials Correlation Factors' relating model and ship results which could be used to improve speed estimates for new ships.

Training The RN College at Greenwich was opened in 1873 and the Royal School at

South Kensington was moved to the new College. Initially, constructors and marine engineers did not wear uniform but this was introduced in 1877.

Engineer students were entered after a competitive examination and were then required to undertake practical instruction at the Steam Factory in Portsmouth Dockyard. The old wooden screw battleship Mnrlborouglz (FIG. 7) (later joined by the Duke of' Wellington) was used as an accommodation ship. In 1879 a permanent training college was opened at Keyham'" in Devonport, initially in addition to the Marlborouglz but in 1888 training was concentrated at Keyham. Initially, Keyham was to provide practical training and all students went on to Greenwich for a final year of theoretical education. By about 1899 it was decided that education and training for most engineers should be completed at Keyham and that Greenwich should be reserved for post-graduate courses.

FIG. 7-HMS 'MARLBOROUGH' A N D HMS 'DUKE OF WELLINGTON' FORMED PART OF THE ENGINEERING COLLEGE AT PORTSMOUTH FROM 1877

Triple Expansion Engines The strength of the steel cylindrical boiler (FIG. g), often known as the 'Scotch'

boiler, led to a rapid rise in steam pressure which, in turn, re-introduced the problems of excessive temperature and pressure in each cylinder of the two-stage compound engine which had led to its introduction. As Isherwood said in 1894,

FIG. 8-A SINGLE ENDED CYLINDRICAL BOILER OF ABOUT 1880, SHOWING T H E CORRUGATED

FURNACE INTRODUCED BY FOX WHICH ALLOWED FOR EXPANSION A N D ALSO INCREASED HEATING SURFACE

'The engine had to follow the boiler, and could only advancepari yassu with it."" The use of three-stage expansion had occurred to many people but it was A. C. Kirk of Elders' who designed the first successful triple expansion for the SS Propontis in 1874. The success of these engines was obscured by the unreliable, experimental, water tube boilers.

Kirk achieved a clearer success with the SS Aberdeen of 1881, using cylindrical boilers working at 125 lb/in2. On trial she burned coal at 1.28 lb/ihp/ hr and on her first round trip to Australia she achieved a consumption rate of 1.7. The first RN ship to use triple expansion was the torpedo gunboat Rattlesnake of 1885 whose engines, in which hollow pistons and connecting rods were used, were regarded as highly successful.

FIG. 9-'VICTORIA'. LAUNCHED IN 1 8 8 7 , S H E WAS T H E FIRST BATTLESHIP WITH TRIPLE EXPANSION ENGINES; THEY DEVELOPED 14000 ihp WITH FORCFZD DRAUGHT. SHE WAS S U N K I N A

COLLISION ON 22 J U N E I893

Victoria (FIG. 9) and Sans Pareil were the first battleships with triple expansion in 1887, and from then on such engines rapidly became universal. It is interesting that, in Sans Pareil, the seed of the replacement for the triple expansion engine appeared in the form of an experimental steam turbo generator. A few cruisers, up to Magicienne of 1887 had horizontal cylinders but almost all triple expansion engines were arranged vertically. From about 1895 (Diadem) the four cylinder engine came into use in which the lower pressure stage was split between two cylinders. The main reason for this was probably to avoid the problems of a very large piston in a single cylinder but the four-throw crankshaft made it possible to achieve a far better balance, reducing vibration and wear.

Early four-cylinder engines were designed to develop equal power in each cylinder but later engines developed one third from each of the HP and IP and one sixth from each LP cylinder. Slide valves were worked off the shaft by conventional link gear. In later engines the valves for the HP and IP cylinders were of piston form. flat valves being permitted for the LP. In some big LP cylinders there were two valves, fore and aft of the cylinder.

Most four-cylinder engines had the two forward and the two after cranks at 180" to each other, the forward pair being at 90" to the after. The Terrible was tried with cranks in a regular series of 90" steps with the two LP aft. This arrangement was found on trial to cause very much more vibration, with an amplitude measured of 1.55 inches against about half that in her sister ship.2s

Quadruple expansion engines were used in a number of fast liners in the early 20th century but by then the RN had already moved to turbines. Warships used a much shorter stroke (213) than merchant ships in order to reduce the height of the engine, and warship machinery had higher piston speeds and revlmin. This gave substantial weight savings, the naval engines delivering about 12 ihplton and passenger liners about 6 to 7 (TABLE I).

TABLE I-Compcrrisorz of power urzd weight between naval and nlerchant ships

Slz 11,

Ayred (cruiser) 30 000 2 500 1 38900 1 5 670

Power

The Thunderer was given an elaborate modernization in 1889-90 which added little to her fighting value but did make possible an interesting comparison between box boilers with simple, trunk engines and cylindrical boilers with triple expansion (TABLE 11). The total weight of machinery and coal was reduced from 2400 to 1750 tons, which enabled 650 tons to be applied to other purposes. On a voyage from Spithead to Madeira at 80% power (4500 ihp) the consumption was 1.67 lb/ihp/hr, about half of what it would have been with the older machinery. White26 suggests that the old machinery would probably not have been able to sustain such power for 2600 miles but, if it did, 1350 tons of coal would have been needed instead of the 650 actually burnt.

Weight tons

TABLE 11-Thunderer 'S mac.lziner?,-a co~nparison c$ old and new

Power developed (ihp) Speed (knots) Weight of machinery (tons) Coal (tons/m~les/speed) Pressure (lb/sq in)

Box boiler; Trunk engine

The triple expansion engine was an almost instantaneous success and was still being built after World War 11. This success depended on a large number of supporting developments, some introduced to cure specific problems, others, perhaps, by coincidence. There were improvements in pistons, in connecting rods, shafts and valve gear while both the theory and practice of balancing was extended. The lubrication of high-speed reciprocating engines was always a problem, largely overcome by enclosed forced lubrication, first introduced in the destroyer Surly in 1899 and rapidly extended to all new ships.

New types of packing for piston and valve rods were introduced, copper steam pipes gave way to lap welded wrought iron, while all valves, joints and fittings had to be redesigned to withstand the higher pressures. Boiler tubes were of brass until about 1882 when lap welded iron and later steel came into use, which almost entirely overcame the old problem of leaky boiler tubes. Steam jackets were further improved.

C).lirzdrical boiler; Triple e.rpansion

6270 13.4 1050 1350/4500/10

5500 (7000, forced) 13.25 800 950/4500/10

rr('/1('r2.Y R(.f (The numbering of the references is continued from Part I. 'Venotes a key source. ~ ~ s e d often even when not specihcally referenced.)

6. Barnaby, K. C. Tlze 111,vtitirtioll o f 'Nrr~~c~/ AI-chirect.~, 1860-1960. London, Royal Institution of Naval Architects, 1960.

16. Ballard. G. A. (Admiral). Tlw hlcrck h(rtt1rflret. Reprinted from articles in Thp Mrrj.irle~:v Miri.or-. Greenwich, Society for Nautical Research, 1980.

17. King. J. W. (Chief Engineer, USN). The n~crr,shi/~.s c!f'Eiri.opr. London, Griffin, 1878. :':l 8. Skelton. R. W. (Engineer Vice Admiral Sir). Progress in marine Engineering. Thomas Lowe

Gray lecture. Pi.oc. 111.stitlrtioi1 of' M~cl~(rr l i (~ i l E11gii1eer.s. 1930. part 1 , pp. 3-36, (Also reprinted in Pcrprrs or1 Ei~giilrer-irlg Slrl?jec.t.s. the forerunner of the .lo~ri-r~c~l of' Nrr~~rl E I ~ , ~ ~ I ~ P ( J Y ~ I I ~ , no. l l . Nov. 1930, pp. 55-1 4 1 . )

19. Roclger. N . A. M. The first light cruisers. T l ~ e Mrrrirlrr-i Mir-mr. vol. 65, 1979. pp. 209-230. 20. Sennett, R. Working and test pressures for marine boilers. Trcrils. Iiz.vtit~rtior~ of Ntr~.trl

Arc,hitect.s. vol. 29. 1888. pp. 207-247. 2 1 . Brown. D. K. Speed on trial. Wrri..rlli/), Lorlllorl, no. 3, July 1977. pp. 56-6 1 . 22. Wright, J . The steam trials of H.M.S. 'Iris'. Trcrr1.v. Irl.vtitlrtior~ of' N ~ I I ~ L I I Ar-cllite(.t.~. vol. 20,

1879. pp. 1 17-132. 23. Denny, W. On the trials of screw steam-ships. Rrpt. 45th 111retii1g c?f'tlze Bi-iti.sll A.s.voc.icitioir,foi-

tllr Acl1~nrlc~rrile11t c!f'Scirrlc,~: I~elrl (it Bristol ir~ Alrgirst 1875. London. 1876. Transactions o f the Sections. pp. 246-247.

24. Penn, G. HMS TIz~ri~clerer Tlze story c$ tlze Ro\.rrI N(II~CII E~~giileer-irlg College Kr~.htrii~ L I I I ~ ~

Mrrnl-rrloil. Emsworth, Kenneth Mason, 1984. 25. Durston, J. A . (Engineer Vice Admiral Sir). The machinery of warships. Proc.. 111stit~ltioil of'

Cillil E11ginrrr.s. vol. 1 19, 189.5, pp. 17-1 18. 26. White, Sir William. A ri~rri~~rcrl c?f'r~o~~crl rrrchitrctur-r. London, John, Murray. 1900 (p. 269).