The Development of Navies During the Last Half-Century/Chapter 11
CHAPTER XI
STEAM PROPULSION
Steam Navy in 1840 — Machinery at that Date — Paddle-Wheel Frigates and Sloops — Horse Power, Nominal and Indicated — Voyage of 'Inflexible' — 'Banshee' — Introduction of the Screw Propeller — 'Fairy' — 'Duke of Wellington' — 'Victoria' — Substitution of Iron for Wood — 'Warrior' and 'Black Prince' — 'Octavia,' 'Arethusa,' and 'Constance' — Progress made up to 1865 — Compound Engines — 'Pallas' — Increase of Boiler Pressure — Twin Screws — 'Inconstant' — Loss of the 'Captain' — 'Iris' and 'Mercury' — Steel Protective Decks — 'Polyphemus' — Forced Draught — 'Lightning' — Yarrow's Boats — 'Rattlesnake' — Triple Expansion — 'Barham' and 'Bellona' — Decrease in Weight of Machinery — Difference between Men-of-War and Merchant Ships — 'Blake' and 'Blenheim' — Large Number of Auxiliary Engines — Supply of Fresh Water — Evaporators — The 'Yaryan' — Growth of Steam in the Navy — Personnel — Probable Approach of Finality in Marine Engineering.
In the year 1840 steam had already made considerable progress in the Royal Navy since, nineteen years previously, the 'Comet' had made her début at Portsmouth. Fifty years ago there were no less than twenty-nine steam vessels whose names appear in the official Navy List. Of these the most important were the ’Cyclops,' 300 horse power, 1195 tons; the 'Gorgon,' 320 horse power, 1108 tons; and the 'Salamander,' 220 horse power, 818 tons. The first two of these ships were engaged at the bombardment of Acre, and the 'Salamander' was employed on the coast of Spain during the Carlist War.
At this period all but three of the steam vessels of the navy were fitted with what were then known as ‘side-lever’ engines. This type was the first ever employed for marine purposes, and it had certain solid advantages which enabled it for a long time to remain the favourite and to resist innovation. So much was it considered to be par excellence the engine for ships that,
SIDE LEVER ENGINE.
surmounted by a crown, it formed the device for the uniform buttons of the engineers in the Royal Navy; in the merchant service it was similarly worn, but without the crown; and, with a lion over it, the East India Company’s engineers adopted it as a distinguishing badge of their class. But in the side-lever engine lightness and compactness were sacrificed to solidity and length of connecting-rod, and as the use of steam gradually spread in the navy, and it became apparent that for every ton saved in the weight of and space occupied by the machinery valuable increase could be effected in the armament and coal capacity of the ship, it was inevitable that the ingenuity of the first engineering country in the world should be directed to the necessity for improvement in marine motive power. Hence we find in 1840 the 'Cyclops,' 'Gorgon,' and 'Prometheus' had been fitted with direct-acting engines[1] by Messrs Seaward, and the total weight of machinery was in their case reduced by about two-fifths. The 'Gorgon' was the first example of the new type of engine, and finished her trials in October 1837, and direct-acting engines soon came into general use in the Royal Navy, although the particular form introduced by Messrs Seaward was by no means that most generally approved or adopted. Still, to them belongs the credit of having been the first in the field.
The year 1843 was a remarkable one as regards the development of steam propulsion in the Royal Navy, for then it was that the 'Penelope,' the first man-of-war supplied with tubular boilers, and the 'Black Eagle,' the first vessel ordered by the Admiralty to be fitted with oscillating cylinders, were added to the list of Queen’s ships. The importance at that date of these two enormous strides in marine engineering cannot be over-estimated. Tubular boilers at once became universal in all ships built for the service, and to this day nobody would dream of applying any but oscillating engines to the driving of paddles. The 'Black Eagle' had side-
ENGINES OF THE ‘BLACK EAGLE.’
lever engines in the first instance, but these were removed and replaced by oscillating ones by Messrs Penn.
In 1846 was commissioned, by Captain William Ramsay, the 'Terrible,' the most powerful steam fighting ship in the world at that date. She was of 1847 tons burthen, carried an armament of twenty-one guns of various calibres, and was fitted with double-cylinder direct-acting engines of 800 horse power by Messrs Maudslay. And here it may be well to digress for a moment to point out to the reader that when speaking of the horse power of the earlier engines 'nominal’ is meant[2] The 'indicated' power developed, that is, the real effective power, varied from about two and a half times the nominal in the case of the 'Gorgon,' in 1837, till it reached more than seven times the nominal in the 'Inconstant,' in 1869. The absurdity and inconvenience of expressing the power of ships’ engines by a system of notation absolutely without meaning became so evident that in 1872 the indicated power was ordered to be given in the official Navy List.
Exactly contemporaneous with the 'Terrible' was the 'Inflexible,' the first steamship in the navy to make a voyage round the world. No better example can be given of the difference between steam navigation in the Royal Navy at that date and the present than the performance of the 'Inflexible,' which was then considered highly creditable, as indeed it was, to Captain John C. Hoseason, who commanded her and furnished an interesting account of it. She was what in those days was called a sloop, of 1122 tons burthen — not to be confounded with displacement[3] — and fitted with direct-acting engines by Fawcett capable of working up to 378 nominal horse power. We have no available record of what her real horse power was, but she probably at her best indicated nearly three times her nominal. Her boilers were loaded to what was then considered the ample pressure of 8 lbs. on the square inch. She was in commission from the 9th of August 1846 to the 28th of September 1849. During this time she steamed 64,477 nautical miles, and got over 4392 under sail alone. Her average daily steaming was 186.62 knots, and her fires were alight during 483 days. Her total consumption of coal was 8121 tons, her average distance steamed per ton of coal 7.9 knots, and her average consumption per hour 19.5 cwt. After service in India and China she returned to England by Cape Horn, thus making the circuit of the globe and establishing a 'record' for herself.
A vessel which must not be passed over among the celebrated paddlers is the 'Banshee,' engined by Messrs Penn, which managed to steam from Holyhead to Kingstown, a distance of 55 nautical miles, in three and a half hours on several occasions, this being at the rate of 15.7 knots, then unprecedented. She was afterwards deprived of half her boiler power, to increase her coal carrying capacity, and sent to the Mediterranean to do duty as a despatch vessel, for which service she could always be relied upon as a 12-knot steamer.
Paddle-wheel men-of-war were at one lime the most important factor in our navy — the manufacture of their engines called forth the utmost skill in design, ingenuity of detail, and accuracy of workmanship that were in those days available — but their end was near, and they were soon to become as obsolete and forgotten as though they had never been. Their defects and disadvantages had all along been sufficiently obvious, but nothing better was to hand. Huge outside cumbrous wheels, liable to be utterly disabled by the explosion of a lucky shell, the position of the engines themselves with their most vital parts well above the water line, and the enormous weight of the machinery in proportion to tonnage and horse power, all these objectionable characteristics made it certain that when an alternative method of propulsion was proposed by which these evils would be abrogated, or even sensibly mitigated, it would be welcomed with enthusiasm and eagerly adopted. The enthusiasm and the eagerness were not quite as much to the front as might have been expected, but the conservatism of the navy even now, much more then, may almost be termed bigotry. The screw propeller, however, had in itself such intrinsic merits that, if it did not at first dazzle like a display of fireworks, it soon became as much a national necessity as the breadstuffs it is the instrument of bringing in such quantities to us who would perish without them.
As has so frequently been the case with other inventions, it is not by any means certain to whom the credit of first discovering the screw as a propeller for marine purposes ought to be ascribed, but the matter is not of much importance. As far as the British navy is concerned, Mr F. P. Smith, who succeeded in rousing the Government to action after that splendid inventor Captain Ericsson had failed, is indisputably the father of screw propulsion. Mr Smith brought out with success in 1840 the 'Archimedes,' a vessel of 232 tons and 80 horse power. The Admiralty thereupon ordered the 'Rattler' to be built on the same lines as the paddle-wheel steamer 'Alecto,' with screw engines of the same nominal horse power by Messrs Maudslay, and very soon several more men-of-war were ordered to be fitted with screws. An early example of a successful screw vessel was the Royal yacht 'Fairy,' built of iron in 1845, and engined by Messrs Penn. She had oscillating cylinders driving a cogged wheel geared into a pinion on the screw shaft, so that the screw made five revolutions for every one of the engines. She was kept running for many years between Portsmouth and Cowes, till at last her plating was worn so thin that a bluejacket alongside sent his boathook right through it. She was then replaced by the 'Alberta.'
The 'Duke of Wellington,' Sir Charles Napier’s flag-ship in the Baltic during the Russian War, was probably the last screw ship in the Royal Navy fitted with geared engines. For it was about this time that a change came over the design of machinery for the propulsion of war vessels, so complete and radical as to mark a distinct epoch in its history. When once the fact had been grasped that all men-of-war for the future would be propelled by the screw, the immense advantage realised by the low position of the main shaft, far below the water line, became apparent, as the engines, being horizontal, would be in a great measure protected from the enemy’s fire, instead of being, as in paddle-wheel ships, dangerously and unavoidably exposed to it. It was also soon seen what great benefit would be derived if the engines were coupled directly to the main shaft, without the intervention of cogged wheels, to obtain the required number of revolutions of the screw. To ensure this result much higher speed of crank-shaft was necessary, but the engineering skill of the country proved quite equal to the occasion. Messrs Maudslay & Field, and Messrs Penn & Son, now began to almost monopolise the Government orders, as I find that of twenty-six sets of screw engines completed for the Admiralty between the years 1852 and 1860 twenty-one are credited to these two firms. The workmanship of both was admirable, but at that time Messrs Maudslay erred, if anything, rather on the side of strength, and Messrs Penn on that of lightness. The number 'twenty-six' given above is exclusive of a large fleet of high-pressure steam gunboats that were built and engined with unexampled rapidity at the beginning of the Russian War. High-pressure steam was first tried in the navy in September 1853, on board the corvette 'Malacca.' She was fitted with engines working with steam at 60 lbs. pressure by Messrs Penn, but she was not a success; engineers had not yet been educated up to so vast an innovation.
In 1860 was completed for sea a ship remarkable from a historical point of view as the last three-decker in commission on active service in the British navy. This was the 'Victoria,' of 120 guns and 4403 indicated horse power. She was fitted by Messrs Maudslay with horizontal double piston-rod return connecting-rod engines, a type they had made peculiarly their own, and from which for a great many years they never varied.
The 'Victoria' relieved the 'Marlborough,' a ship of a similar kind, but of only 3054 horse power, as flag-ship of the Commander-in-Chief on the Mediterranean station. Her engine-room, as compared with the cramped chambers of modern vessels, was of palatial dimensions. The pressure of steam in the boilers was 22 lbs., and at full power the ship attained a speed of over 12 knots. With sail set on her enormous yards, and her progress perhaps helped by her screw, she was a magnificent sight as she made her way in or out of the harbours of Malta or Corfu. But her day had come; she was the last of her race, for it was recognised that in combat with even an ironclad of her day she could have been nothing but a floating shambles. She is, however, worthy of mention here as being probably the finest specimen of a wooden steam man-of-war the world has ever seen. She had but that one commission, and is now for sale to be broken up.
Various causes were now combining to bring about the substitution of iron for wood, but there is no doubt the necessity of providing against the vibration of the screw in high-powered vessels had a great deal to do with it. Iron had been used to a limited extent in the navy, but had not been at all generally approved of. The frigate 'Vulcan' was completed in 1849, and the troopships 'Megaera' and 'Simoom' in the following year, but it was not till June 1859 that the 'Warrior' was ordered as a counterblast to the French 'La Gloire,' then on the point of completion by M. Dupuy de Lome.
Although this constituted so distinct a landmark in the history of the British navy, it had little or no influence on engineering practice. Engines were made bigger as higher speeds were demanded, but, except in the matter of size, the engines of the 'Warrior' and the 'Agincourt' differed but little from those of the ’Arrogant' and the 'Cossack.' It is true the pressure of steam in the boilers had gradually crept up to 25 lbs. on the square inch, some improvements in detail had also, as was natural, been introduced, but the general principle and arrangement remained unaltered. The engines of the 'Warrior,' however, when she was first commissioned, were considered to involve so vast a responsibility and to require such effective supervision that it was decided to take the unprecedented step of appointing two chief engineers to her, whereas to-day the post would unhesitatingly be given to the junior Chief Engineer of the Fleet, if it happened to be vacant and he to be unemployed. Messrs Penn & Son obtained the contract for these engines, as also for those of the sister ship 'Black Prince.' And here a most curious fact may be mentioned which excited a good deal of speculation at the time. The designs for the two ironclads were got out at the Admiralty by Mr Watts, Chief Constructor of the Navy, in consultation with Mr Scott Russell, and identical drawings were sent to the contractors, the Thames Iron Shipbuilding Company and Messrs R. Napier & Sons, of Glasgow, for their information and guidance. The engines were in every way duplicates, of course. And yet the 'Warrior' was, and is to this day, appreciably superior, both in steaming and sailing, to the 'Black Prince.' Many ingenious explanations for this difference were proposed, but none that could in any way be called convincing.
At the latter end of 1860 the Admiralty, being perturbed in their minds at the large amount of the national coal bill, gave carte blanche to three eminent engineering firms to construct machinery for three crack sailing frigates of nearly similar tonnage and lines, with the sole view of combining reasonable speed with economy of fuel. The selected frigates were the 'Octavia,' Arethusa,' and 'Constance,' which were assigned to Messrs Maudslay, Penn, and Randolph & Elder respectively, with no restrictions as to pattern or, it was said, price. Messrs Maudslay elected to supply a three-cylinder engine, working expansively in the ordinary way, with an initial pressure of 30 lbs., which they afterwards reproduced on a larger scale in the 'Lord Warden'; Messrs Penn fitted an exceptionally well executed specimen of their trunk engine, but about neither of these designs was there any decided novelty. The Scotch firm, however, flew at higher game. They had six cylinders to their engines, each triplet consisting of a high-pressure between two low-pressure ones. The initial pressure in the boilers was 60 lbs.; steam was cut off in the middle cylinder of each group at about half-stroke, and exhausted thence into the other two. This deserves notice as being the first instance of the use of the compound engine in the navy, though it was not long after the trials of the 'Constance' that Messrs Humphrys & Tennant employed a simpler form of the same principle in the 'Pallas.' The three ships were sent for a cruise in company to Madeira and back, but no very grand results were obtained. The 'Octavia' became commodore’s ship during the Abyssinian War, the 'Constance' went to the West Indies, and the 'Arethusa' to the Mediterranean. After one commission they were never employed again; they were admitted to be failures, and their hulls have long since gone to the shipbreaker, their engines to the scrap heap.
Let us look, then, at the state of steam navigation in the Royal Navy in 1865, the year that marks the close of the first half of the fifty years that this book deals with, and great as the progress made, and radical as the changes introduced in this quarter of a century may seem, they certainly did not surpass in importance either the progress or the changes of the next. In 1865 the paddle-wheel as a mode of propulsion for fighting ships had become entirely obsolete, its place having been taken by the screw. The pressure of the steam in the boilers had increased from 7 lbs. in the 'Rattler' to 30 lbs. in the 'Vestal,' which of itself shows what an advance must have taken place in the art of boiler construction, and every boiler afloat was on the tubular principle. The interposition of gearing between the crank and main shafts had long been abolished, and the number of revolutions of the engines had risen from, say, fourteen to fifty-six. The question of coal consumption was beginning to awaken attention, and as a consequence compound engines and surface condensers were being toyed with tentatively to that end. The 'Warrior,' though completed in 1861, was still the fastest ship we had, with her speed of 14.3 knots, and it was not then considered likely that this speed would be much exceeded in the future except by a few enthusiasts; but the gift of prophecy is rare, and it is possible that a quarter of a century hence the engines of the 'Blake' will be considered as antiquated as those of the 'Warrior' are now. The engine builders of 1865, however, enjoyed advantages of which their successors of to-day may well be envious. The girders of ironclads, the solid oak beams of frigates or converted line-of-battle ships furnished such sound foundations for the bed-plates of the engines, and, above all, the restrictions in the matter of weight were so comparatively benign, that delightful smoothness of working was the rule, and serious accidents were all but unknown.
We now enter on a new era of naval marine engineering. In 1866 was completed the 'Pallas,' a small ironclad designed by Sir E. Reed, and remarkable for having been the first ship successfully fitted with compound engines for the Royal Navy; for though the 'Constance' preceded her, that ship’s machinery was a constant source of extreme worry and anxiety to those responsible for the charge of it, while the 'Pallas' in this respect never gave any trouble at all. The 'Pallas' had only two cylinders, instead of six, of unequal volume, one being four times the size of the other. The steam was admitted at high pressure, 60 lbs., into the small cylinder, and thence passed into the larger one, which it of course filled by its expansion. This is the whole principle of compound engines. She had surface condensers, and there is no doubt, for the horse power produced, she was very economical in fuel. The boilers were fitted with superheaters, a series of tubes at the base of the funnel through which the steam passed with the object of drying it and surcharging it with heat — a contrivance that was always looked upon with distrust by naval engineers and has long ago passed into oblivion. Her speed was 13.4 knots, and she was a handy and essentially comfortable little ship.
The compound principle, as introduced by Messrs Humphrys & Tennant for the 'Pallas,' was, but at an interval, adopted for most of the new ships in the navy, until superseded by triple-expansion, to a consideration of which we shall come by-and-by. With compound engines came as a natural consequence surface condensers, and the general use of steam of not less than 60 lbs. pressure. This latter innovation brought about an entire revolution in the shape of ships’ boilers. What was known as the square or 'box' type, that had been in use nearly fifty years, had to be discarded, in view of this increase of pressure, for a circular form, resembling a Gloucester cheese set on edge, with the furnaces on the flat side of it. The thickness of plates had to be greatly increased, the excellence of the metal to be more rigidly insisted on, while the difficulty of manufacture was considerably enhanced. Machines that had been devised for punching out the rivet holes became of no value, as thick plates suffered in strength by the process, and the operation of drilling had to be substituted for it. This was, of course, more expensive, but amply repaid its cost in the long run.
The 'Penelope,' completed in 1868, was the first important ironclad fitted with twin screws, and is noteworthy as having been the forerunner of a long line of twin-screw battleships. When the 'Audacious' class came to be built, immediately following on the 'Penelope,' the twin screw system was not so generally accepted, as two ships of the same type, the 'Swiftsure' and 'Triumph,' were only allowed one screw apiece. Nowadays all vessels we build of any size above second-class gunboats are fitted with two sets of engines. Of the advantages of the plan there can be no doubt, but in this place, where the aim is to be rather historical than critical, any disquisition on the subject would be impertinent — in the original sense of the word.
In August 1869 was commissioned a single-screw frigate that for speed and other good qualities excelled everything the world had hitherto seen, and indeed she has never been beaten in her own line. This was a period of experiment and invention, and the 'Inconstant' was in many ways an example of success in both. She was the first iron ship to be encased in a sheathing of wood, in order that she might be coppered, and so avoid the inconveniences of the fouling which, in spite of so many compositions and nostrums, is still the bête noire of all iron and steel hulls. Her engines were supplied by Messrs Penn, and were nominally of 1000 horse power, but when the ship was tried on the measured mile at Stokes Bay they indicated 7360 horse power, and gave the ship, when all her ten boilers were used, a speed of 16.51 knots, which had never hitherto been approached by a fighting ship. With half-boiler power a speed of 13 knots was easily attained, but the 'Inconstant’s' weak point was her limited coal endurance. Her supply of fuel was only sufficient for two and a quarter days’ steaming at full power, and for nine days at 10 knots an hour. This, of course, is a serious defect, but nevertheless she was a splendid ship in her day. She was remarkable for her speed and handiness under sail alone, and when the squadron was sailing showed herself superior to the 'Bristol,' a wooden frigate of no mean reputation.
But a time came when she was asked to show her speed under circumstances so sad and melancholy as to fill the whole kingdom with grief and mourning. On the night of the 6th of September 1870 the Channel Squadron, under the command of Sir Thomas Symonds, was cruising off Cape Finisterre. The weather after leaving Gibraltar, had been remarkably fine, and the admiral had taken advantage of the smooth water to launch his boat from the 'Minotaur' flagship and inspect the 'Captain.' He did not approve of her, although at that time, because she had made one or two cruises without capsizing, she was supposed to have settled the question beyond dispute as to what should be the type of the British war vessel in the future. There was no particularly bad weather that night; the sea was certainly not exceptionally heavy, nor the wind anything like a real gale, but in an ordinary squall the 'Captain' turned slowly over and 500 precious lives were lost. The 'Inconstant' was the next ship to her, and remarked the disappearance of her lights, but owing to the squall the squadron was more or less scattered, and but little attention was paid to the circumstance. When daylight came next morning the sea was smooth, but there were no signs of the 'Captain,' and at first no alarm was felt about her. The admiral, however, made a general signal, 'Spread in search of "Captain,"' and it was not long before one of her boats was picked up; still nobody suspected the dreadful truth. But later in the day a table known to have formed part of Captain Burgoyne’s cabin furniture was found floating, and then there was no room for doubt. Nothing but the capsizing of the 'Captain' could have caused that table to be floating in the Bay of Biscay. A signal was then made for the 'Inconstant' to get up steam for full speed and proceed to England with the terrible news. She had a light fair wind, and from a point just off Corcubion to Plymouth she averaged 15¾ knots, with one boiler out of her ten held in reserve. This was a fine performance in those days, but she never had the chance of repeating it, for the scare caused by the loss of the 'Captain' resulted in some 300 tons of extra ballast being stowed in her hold, which had the effect of completely ruining her exceptional qualities for speed, whether under steam or sail. She has been employed on various services since then, but is now quite obsolete.
By 1873 the engineer department at the Admiralty finally made up its mind that compound engines were as likely to be profitably employed on board the Queen’s ships as they long had been in the mercantile marine. The usual pressure of steam in the boilers of men-of-war had now settled at 60 lbs. on the square inch. Every ship as she was built was being fitted with compound engines, but there was a restless, uneasy feeling among the men who constructed them that they were very far from the end of the journey on which they had started when they first left the 'sweet simplicity' of simple engines and 30 lbs. pressure behind them. They little knew what was in store for them in the future.
Before that time arrived, however, two ships were added to the navy sufficiently remarkable both for hulls and machinery to demand particular notice. These were the 'Iris' and 'Mercury.' Entirely without defensive armour, these ships were intended to rely for safety on their exceptional speed. The 'Iris' was the first ship built in England in which soft steel was employed, and the first vessel of the Royal Navy wholly built of steel. It may be added that she was also the first vessel wherein the construction of her machinery was much hampered by considerations of weight, and as a consequence in her engines were introduced, for the first time, hollow compressed steel shafts, invented by the Whitworth firm. The engines, by Messrs Maudslay, were indeed of a type entirely new to the navy. The firm had obtained considerable credit and renown by the extraordinarily fast passages made by the 'Germanic' and 'Britannic,' Atlantic mail steamers engined by them for the White Star line. The compound engines of the 'Iris' are exactly on the same principle, but horizontal instead of vertical. There are two distinct sets, driving twin screws, and each set has four cylinders, two high-pressure at the back of the two low-pressure ones, arranged in what is known as 'tandem' fashion. ‘The narrow beam of the ship, in proportion to the size and power of the engines, rendered it necessary to place the starboard engine in front of the port engine, so that the whole body of the ship is filled with machinery.’ So says Lord Brassey, but what was considered an exceptional case in 1876 is now the universal order of things.
The 'Iris' carries 500 tons of coal in the ordinary bunkers, and 250 tons additional in the reserve bunkers. The total weight of the machinery, with water in the boilers and condensers, is about 1000 tons, and the contract price was £93,000. From the Times account of her trials we learn that she proved to be not only the quickest ship in the navy but the quickest ship afloat 
THE ENGINES OF THE 'IRIS.'
Space does not permit of any detailed description of the numerous experiments which followed, but it is sufficient to say that the screw propellers were found to be vastly too large in diameter, and their friction in the water was thus excessive, that their pitch was increased, and that the 'Iris,' with 7735 horse power, attained a mean speed of 18.572 knots, fully a knot more than the constructive department at the Admiralty ever expected to get out of her. The 'Mercury,' her sister ship, built on the same lines, under an adjoining shed at the same dockyard, and engined by the same firm, was even more successful, attaining a mean speed of 18.87 knots per hour, and this in 1879. It is hardly to be wondered at that the fame of such unparalleled achievements spread all over Europe and excited the emulation of foreign powers, but at that time they had neither engineers nor shipwrights who could pretend to rival ours.
It has been thought desirable to dwell at some length on the 'Iris' and 'Mercury,' because they undoubtedly indicate an epoch in the history of engineering in the navy and are still very valuable vessels. They have, however, two grave defects, which have prevented any reproduction of their type. They are entirely unprotected, and their coal endurance is very small. More or less provision was made in them to compensate for the absence of armour by water-tight subdivision and by coal protection; still they had to run the risk of being penetrated in a vital part and sent to the bottom by the explosion of a single successful shell.
And here came in one of the most important inventions, suggestions — call it what you will — of the quarter century we are discussing. That was the adoption in otherwise light cruisers of a steel protective deck, which has permitted the grand and beneficial substitution of vertical engines for horizontal ones. And for this idea Rear-Admiral Robert Scott deserves all the credit. The part of a fighting ship that it is most essential to guard from an enemy’s fire is the engine-room. In the early days of steam this was naturally accomplished by keeping all the machinery below the water line, but when the idea of a horizontal armoured deck took root engineers were quick to see that they would be comparatively safe under its shelter, and that projectiles would glance off it instead of dropping through to their destruction. Hence vertical engines, whose height is only limited by that of the protective deck. Every engineer knows that the normal position of a cylinder and piston is perpendicular; circumstances alone have forced him sometimes to be content with the horizontal. At the present time every war vessel of size above a gunboat is supplied with vertical engines. The 'Shannon' and 'Dreadnought,' both built at Pembroke, and the 'Nelson' and 'Northampton, both hailing from Messrs Elder, of Glasgow, were the first important ships to be so fitted. These four ships were all completed between 1875 and 1878.
In 1881 was launched the 'Polyphemus,' a most remarkable ship, but noteworthy more for her hull, which is fully described elsewhere, than for her machinery. She has twin screws, driven by two pairs of compound horizontal engines constructed by Messrs Humphrys & Tennant, of Deptford, who, it may here be remarked, have latterly built and are building some of the most important engines in the navy. The boilers of the 'Polyphemus,' originally of the locomotive type, gave a great deal of trouble, and new ones were substituted for them with good results. The pressure of steam is 110 lbs. per square inch. It will be observed with what leaps and bounds the pressure of steam advanced in the course of comparatively few years. A quite usual pressure now is 155 lbs., and this will probably be very considerably increased before long.
With the extended application of high-pressure steam came, as a natural corollary, a desire to utilise its advantages to the utmost. To this laudable ambition we owe the introduction of forced draught and triple expansion. The former device, which, for the benefit of lay readers, may be defined as the increase of air pressure in the stokeholds by artificial means, causing the fires to burn more fiercely and to consume more fuel in a given time on the same surface of grate, was, like other new things, only generally adopted in our service after considerable hesitation, and when it had been proved by the French to possess certain advantages too weighty to be overlooked. It may be well here to observe that this is probably the first and only instance of British marine engineers owing anything to any foreign source. Other nations have invariably been content to follow where we led from the very earliest days of steam navigation. In the future it is possible that the restless ingenuity of American mechanicians may produce ideas that we cannot afford to neglect, but at present it may safely be said that the history of English engineering includes all that the rest of the world has hitherto accomplished in that direction.
Forced draught was first employed in the British navy in the 'Lightning,' our earliest torpedo boat, constructed by Messrs Thorneycroft, of Chiswick, in 1877. The system was adopted, primarily if not solely, with the view of obtaining a much greater power with a given weight of boilers than could be obtained with natural draught. Economy of fuel was not the object sought; if it had been, it would not have been found. The 'Lightning,' a boat only 84 ft. long, of 10 ft. 10. in. beam, and 32 tons displacement, attained a mean speed of over 18 knots. Her engines, supplied by her builders, were compound, driving a single screw. The high-pressure cylinder was 12¾ in. in diameter, the low-pressure 21 in., their stroke was 12 in. She had a steel boiler of the modified locomotive pattern, working at 120 lbs. pressure. Her surface condenser was made of thin sheet copper, and was supplied with a separate engine and centrifugal pump. The machinery of this vessel was very light, steel being largely used, and the workmanship was of the highest class. She was, in her day, a complete novelty, both as regards hull and machinery, and was equally a complete success. She is interesting as the pioneer of a very numerous and important flotilla. By May 1887 Messrs Yarrow, of Poplar, who have always been friendly rivals of Messrs Thorneycroft, had supplied our navy with a torpedo boat, known as 'No. 80,' which illustrates the strides that had been made by both firms in a decade. This vessel has a length of 135 ft., beam of 14 ft., and displacement of about 130 tons. Her triple-expansion engines work up to 1700 indicated horse power, and the trial speed for three hours was 23 knots. She can steam a distance of 2000 knots at 11 knots speed. There is only one locomotive boiler, and it is probable the boilers of this type of boat are the largest ever built on the locomotive principle, but the firm has as yet had no failures with them. Higher speeds with more powerful machinery have been attained in boats built since 'No. 80' by both firms for foreign powers. Messrs Yarrow have recently employed quadruple-expansion engines, with a boiler pressure of 200 lbs., in a boat for the Argentine Government, with the happiest results.
It has been stated that 'No. 80' was supplied with triple-expansion engines, but she was not the first vessel to be so fitted. Here it may be well to mention that whereas in simple engines the whole process of expansion of the steam is carried out in one cylinder, and in compound engines in two, in triple-expansion engines the steam passes through three cylinders, diminishing in pressure at each step before it reaches the condenser. More work is thus got out of the steam for the same expenditure of fuel, and consequently what is known as the 'coal endurance' of ships is considerably increased.
In September 1886 was launched the 'Rattlesnake,' built and engined by Messrs Laird, of Birkenhead, the forerunner of a type of vessel considered by many good judges to be of even more importance in modern naval warfare than the torpedo boats. That the authorities themselves are of this opinion may be seen by the fact that at the present moment there are twenty-two of these vessels, now known as 'sharp-shooters,' either completed or in progress. 'In engining these ships the paramount object has been to reduce all weights to a minimum consistent with efficiency,' and in no similar instance has praiseworthy intention been so carried to an extreme as nearly to approach a crime. The propelling machinery of the 'Rattlesnake,' consisting of two sets of vertical triple-expansion three-crank engines, of 2700 horse power at 310 revolutions, was the first of its kind supplied to the navy. The framing is entirely composed of steel, which has also been largely employed in the construction of the machinery throughout. The crank and other shafts are made of Whitworth special steel, and are all hollow. She attained a mean speed of 18.779 knots on the measured mile under unfavourable circumstances as regards weather, and has since then frequently achieved 19 knots on actual service. She has taken an active part in all naval manoeuvres of late years, and has been the terror of her imaginary foes, mainly because her engines have never broken down. This is no doubt owing to the fact that the stipulated weight of the machinery was exceeded.
The great difficulty in obtaining and maintaining high speeds in the navy has been the incapacity of boilers to withstand the strain put upon them. For this contracted dimensions have been mainly, and forced draught excessively and injudiciously applied, partly responsible. Forced draught is by no means to be wholly condemned. It is not, as Admiral Mayne called it, purely 'an invention of the Evil One.' But it requires to be used with care and judgment, when it will probably prove as valuable an auxiliary to the steaming power of our warships as it has undoubtedly shown itself to be in the mercantile marine. The 'Barham' and the 'Bellona,' sister ships, deserve a few words as to their machinery, which is very fin de siècle. They have each two sets of vertical triple-expansion engines, driving twin screws. The cylinders are 27 in., 40 in., and 60 in. in diameter, with a stroke of 2 ft. 3 in. The natural draught trial of the 'Bellona' took place in November 1890 in the North Sea, off the mouth of the Tyne, and in a run of six hours she attained a mean speed of 19.46 knots. The mean indicated horse power was 3557. Why could the 'Barham,' fitted with precisely similar engines, only keep up a speed on active service of 2 knots less? In all likelihood it was the human element that came into play and caused the difference. The stokers were not good enough for their work.
Here it may not be inappropriate to call attention to the rapidly diminishing weight of steam machinery for warships in proportion to the power demanded from it. In the year 1853 the 'The Duke of Wellington' was looked upon with pride by the whole country as a magnificent specimen of a steam line-of-battle ship. Her engines were of 1999 indicated horse power; they weighed 400 tons, so that each ton of engines gave 5 horse power, and each horse power was produced by 448 lbs. of machinery. In the 'Bellona' the horse power is 6000—estimated—and the weight of machinery only 270 tons, which gives approximately 100 lb. per horse-power. In torpedo boats the proportion is very much less than this, which all marine engineers have agreed to consider as extravagantly small. 'In the merchant service our tonnage laws encourage the shipowner to build roomy engine-rooms, and consequently the engines are not limited as to space occupied; hence a better design is possible than obtains in the navy. In our mail steamers on the Atlantic the weight of machinery per indicated horse power is about 280 lbs.' This shows, says the Liverpool Journal of Commerce, how impossible it is to institute comparisons between a merchant vessel and a warship. The question is constantly asked by outsiders why it is that the ships of the Royal Navy cannot make passages equal to those achieved every day by the Atlantic 'greyhounds.' The answer is that they are not built for it. In, say, the 'Teutonic' the propelling machinery is made the great consideration. Everything is, and can be without harm, sacrificed to it. But it is far different in a man-of-war. As was long ago remarked, a fighting ship must always be a compromise. There are three great requisites: offensive power, meaning guns and torpedoes; defensive power, meaning armour, whether applied to sides, turrets, barbettes, or decks; and speed, meaning the most powerful engines, combined with the greatest coal endurance, that it is possible to get a ship of given tonnage to carry. If the tonnage is a fixed quantity, every attempt at extension in the direction of any of these three qualities can only be made at the expense of the other two. Hence the craze for inordinate lightness of machinery.
As the very latest development of extreme steam power, with the view of giving to a warship unprecedented speed, attention must be called to the as yet uncompleted cruisers 'Blake' and 'Blenheim,' engined respectively by Messrs Maudslay and Messrs Humphrys. It is probable that there will be but little difference between them, as far as steaming capabilities are concerned, and so the account, taken from The Times, of the 'Blake's' machinery may answer for both vessels, which are, from many points of view, the most important that have been ordered for the Admiralty for many years. The 'Blake' "will be propelled by twin screws, driven by four sets of triple-expansion engines of the inverted vertical cylinder type. Messrs Maudslay, Sons & Field are the makers of these engines and boilers. The collective power they guarantee is 13,000 horse power for twelve hours' steaming at natural draught, and 20,000 horse power for four hours with forced draught; the corresponding maximum speeds are estimated at 20 knots for natural draught and 22 knots for forced draught, when the vessel is run in smooth water with everything at its best. On actual service, judging from past experience, with ordinary conditions of coal and stoking, the engines may be expected to develop about 9000 to 10,000 horse power for long periods of continuous steaming, which would probably give the vessel a continuous speed of 18 to 18½ knots in smooth water Everyone knows, what recent manœuvres have illustrated afresh, that in cruisers of moderate dimensions, capable of attaining high speed in smooth-water trials, the working speeds at sea are limited by other considerations than the power available for propulsion Sailors generally will be sure to welcome the greater length and size of the 'Blake' and 'Blenheim,' because of their capability of maintaining speed in rough water; and their enormous engine power and very high trial speeds give 
The Engines of The Blake.
Perhaps in nothing has the advance of the use of steam on board warships been so extraordinary as in the number of auxiliary engines now considered necessary. And this is a source of danger. The 'Sans Pareil,' for example, has in addition to her main engines no fewer than fifty-eight auxiliary steam engines on board. Some of these are only used occasionally for special purposes, but an enumeration of them will show that many must be constantly in use. They are as follows:—
| Main circulating engines, | 4 |
| Auxiliary condenser do., | 2 |
| Main fire engines, | 2 |
| Auxiliary do., | 2 |
| Bilge engines, | 2 |
| Turning engines, | 2 |
| Reversing engines, | 2 |
| Distilled water, | 2 |
| Drain tank, | 1 |
| Evaporator feed, | 2 |
| Ventilation supply, | 4 |
| Ventilation exhaust, | 2 |
| Forced draught, | 8 |
| Main feed, | 4 |
| Auxiliary feed, | 4 |
| Air compressing, | 4 |
| Dynamo, | 3 |
| Capstan, | 1 |
| Hydraulic pumping, | 2 |
| Auxiliary do., | 1 |
| Friedman's ejectors, | 4 |
When the ship is at sea it is clear that these engines, many of which are constantly at work, and all of which must be ready to work on an emergency, will consume an appreciable proportion of the coal assumed in the official tables to be available for the purpose of continuous steaming at 10-knot speed, as the consumption for auxiliary purposes varies from about 5 to 8 tons a day.
It will readily be understood that the supply and economy of coal on board a fighting ship are matters of the very utmost importance, and any contrivances tending to facilitate them are of great value, but it is probably less well known that the health and efficiency of modern marine boilers depend very largely on there being no stint in the supply of fresh water for them. Such, however, is the case. Any appreciable admixture of raw sea water is fatal to the delicate constitutions of boilers working at a pressure of 155 lbs. on the square inch. Hence special arrangements have to be fitted for making up the necessary waste of fresh water that must occur during a voyage of very moderate length. Theoretically, if machines were perfect, the fresh water taken in from the shore, converted into steam in the boilers, and reconverted into fresh water by the surface condensers, would not diminish in quantity and might go back to the boilers from week's end to week's end on its round of profitable employment. But, in practice, what with unavoidable leaky joints and occasional escapes of steam at the safety valves, it is found that there is a deficit of hundreds of gallons of water every day, which has to be made up. To this end all ships are now fitted with distilling apparatus, or 'evaporators' as they are generally called, for the purpose of converting salt water into fresh, not only for the use of the boilers but also for the use of the crew. The newest of these, and apparently by a long way the most efficient, is the Yaryan, of American origin, the main principle of which is that the sea water before being evaporated and condensed is pulverised into spray. Professor Lewes, of the Royal Naval College, speaking of most of the other varieties, averred with good reason that the trouble of deposit in the boilers was only transferred to the distillery apparatus; in the Yaryan there has been no trouble at all, because there has been no deposit.
Looking back, then, on the past half century, we find that the whole aspect of marine engineering has changed. And nowhere is this revolution more distinctly marked than in the Royal Navy, where it has produced its most startling effects. In the early days the steam engine was seldom used, and occupied a very minor position in the internal arrangement of a ship, but now it is absolutely requisite for every purpose for which the modern man-of-war exists. Steam machinery now fulfils every function of the latter-day ironclad. Its very air and light, its steering and anchoring, the training and loading of its guns, the motive power of its torpedoes, all these, and many other things, without steam could not be. As a matter of course, as steam machinery became of more and more importance in the navy, so did the position of the officers in charge of it advance. Before 1847 all engineers were warrant officers, but junior of that rank, so that the chief engineer of a paddle-wheel frigate was then, officially, of less account than the carpenter. He is now, as far as rank goes, on the same level as the medical and accountant officers, but his pay is considerably less than theirs, which is a constant occasion of complaint With regard to the rank and file of the engine-room, the introduction of a class of skilled artificers, which took place in 1869, has proved of very great benefit to the navy, by rendering it possible to reduce very largely the number of highly trained engineer officers, which reduction has, however, been carried too far. The entry and training of stokers — firemen as they are called in the mercantile marine — are in anything but a satisfactory state. As the necessity for increased intelligence among these men becomes more manifest, on account of the number of small yet anything but simple engines that have to be confided to their care, it will probably be found advisable to train them up from boys for their particular duties, in the same way as has long been the practice with seamen. What the future of engineering in the navy may be he would be a bold man who would attempt to prophesy. It is, however, unlikely that in the next decade anything like the same progress will be made as in the past one. There must be a point beyond which, except in matters of detail, improvement of the marine steam engine cannot go. That point has probably very nearly been attained. To the ambitious and sceptical it may be called to mind that, with every inducement, to inventors, no substantial difference exists to-day between the best example of a railway locomotive and one of thirty years ago. If any startling revolution in the economy of marine steam propulsion does take place during the lives of the present generation it may possibly be in the direction of the substitution of liquid fuel for coal. But of this there does not seem to be at present any noticeable sign.
- ↑ ‘The distinguishing feature of all direct-acting engines consists in the connecting-rod being led at once from the head of the piston-rod to the crank without the intervention of side-levers.’ But this is very ancient history.
- ↑ 'Nominal' horse power was a standard adopted by James Watt for commercial purposes, in which the effective pressure and speed of piston were assumed to be constant quantities in all engines. The rule was well enough when first devised, but the extraordinary thing is that it should have remained in force so long under such entirely different conditions.
- ↑ 'Tons burthen,' or old measurement as it is often called, was, like 'nominal' horse power, a purely commercial expression. It was obtained by multiplying the 'length for tonnage' — which was found by deducting three-fifths the breadth of the ship from the length, taken at the water line — by the whole breadth and by the half breadth and dividing the product by ninety-four. Displacement tonnage, now in universal use, means the number of tons weight of sea water displaced by a ship floating at her load draught.