In these days of feverish activity in every avenue of business, when even leisure has come to be observed at a much more accelerated tempo than formerly, speed in locomotion would seem to be the first desideratum, not only on shore but afloat as well. In no ocean service is the truth of this so apparent as in the transatlantic mail and passenger service, the oldest and most constantly progressive, and where at the present time, certainly more than at any former period, the contest for supremacy amongst rival steamship lines has assumed the form of increased speed and enhanced passenger accommodation.
The Atlantic service, for these reasons, as well as because it exemplifies more of the fruits which have rewarded the joint labours of the engineer and shipbuilder in improving marine propulsion, may be selected for detailed review. In other ocean services, of course, the achievements of engineering and shipbuilding skill have also been made apparent, and in ways, perhaps, which the Atlantic service does not exhibit. Reference to these will afterwards be made, but attention will meantime be confined to the service stated, and to such considerations of the general progress made in ocean navigation as are necessarily involved in the particular subject.
It is needless, in view of the frequency with which the story of ocean steam navigation is told, and especially, considering the scope of the present review, to enter at any length into the details of early service. The first practically successful transatlantic steamers were the Sirius and the Great Western, the first a paddle-steamer 170 feet long, 270 horse-power originally constructed to ply between London and Cork, and the latter, a paddle-steamer, 212 feet long and about 440 horse-power, designed and built expressly for the transatlantic service. The Sirius left Cork on the 4th April, 1838, and reached New York on the 22nd; the Great Western left Bristol on the 7th April, three days after the Sirius, reaching New York on the 23rd—the time taken being thus 18 days and 15 days respectively. The return voyages of these pioneer long-passage steamers were made in 16 days and 14 days respectively, their performances at once establishing the superiority of steamers, commercially and otherwise, over the sailing ships which had previously for so long been the recognised medium of transit in the Atlantic passenger trade.
In 1840 a regular mail service by steamers was first introduced on the Atlantic. The first of these mail steamers was the Cunard paddle-steamer Britannia, 207 feet long, which sailed from Liverpool on July 4, 1840, and arrived at Halifax in 12 days 10 hours, the return journey being performed in 10 days. The Acadia, Columbia, and Caledonia all of about the same dimensions as the Britannia, at once followed. The success of the Cunard Line was so marked that opposition was soon provoked, and in 1850 the Collins Line of American steamers started to compete with the Cunard liners. The same year also saw the commencement of the well-known Inman Company, of Liverpool, their first vessel being the City of Glasgow, an iron screw-steamer of 1680 tons and 350 horse-power. The Allan and Anchor Lines were established in 1856, the Guion Line in 1863, and the White Star Line in 1870.
With the substitution of the screw propeller for the paddle wheel, first carried out to any great purpose in the small steamer Archimedes in 1839, but introduced with even greater effect in the Atlantic steamer Great Britain in 1843, was laid the basis of that progressive and magnificent success in propulsion which has since attended ocean navigation. It was with screw-steamers Mr Inman boldly assailed the Cunard Company in 1850, but notwithstanding this, it was only in 1862 that the Government consented to sanction the use of the screw in the mail steamers of the Cunard Company. The Scotia, measuring 366 feet in length, by 47½ feet in breadth, and 30½ feet depth, launched in 1861, was the last paddle-steamer built for this company.
The other great improvements contributing to the success spoken of, were the introduction of engines designed on the compound principle, and a little later, the employment of the surface condenser, and the use of circular multitubular boilers. In spite of the success with which the compound system was attended in vessels built for the Pacific Steam Navigation Company as early as 1856, and for some other private owners soon after, the great steamship companies, and shipowners generally, were very slow to adopt it. It was not until about the year 1869 that the compound engine came into general use, and it was only in 1872 that the Cunard Company seriously took it into favour.
The early steamers of the Cunard Line possessed an average speed of 8½ knots, and took about 15 days for the voyage. Through the Collins rivalry the speed was increased to an average of 12½ knots, and the time for crossing the Atlantic was reduced to 12 days 9 hours outwards, and 11 days 11 hours homewards. In 1856, the powerful paddle-steamer Persia (the first iron vessel built for the Cunard Company) was placed on the service, and attained an average speed of about 13 knots, consuming 150 tons of coal per day. She made the distance between Queenstown and New York, on an average, in 10½ days. In 1862 the Scotia, belonging to the same company, made the passage in 9 days.
Coming down to more recent times, the White Star Line, with its steamships Britannic and Germanic, built in 1874 and 1875 respectively, held for a considerable period first place in the matter of fast steamships. The vessels named were, however, in time beaten by the newer ships Gallia, of the Cunard Line, and Arizona, of the Guion Line. As illustrating the speed at which the vessels named accomplished the transatlantic voyage—between Queenstown and New York—the following brief list, compiled from published records, of fast runs out and home during the period 1875-1881, may here be given:—
| Vessels. | Out. | Home. | ||||||
|---|---|---|---|---|---|---|---|---|
| Date. | Time. | Date. | Time. | |||||
| D. | H. | M. | D. | H. | M. | |||
| Britannic, | Aug., 1877, | 7 | 10 | 50 | —— | —— | ||
| Britannic, | May, 1879, | 7 | 13 | 7 | May, 1880, | 7 | 19 | 22 |
| Germanic, | Oct., 1880, | 7 | 13 | 0 | Nov., 1881, | 7 | 17 | 34 |
| City of Berlin, | Oct., 1877, | 7 | 14 | 12 | Oct., 1875, | 7 | 15 | 48 |
| City of Berlin, | Oct., 1880, | 7 | 20 | 32 | Sep., 1879, | 7 | 19 | 23 |
| City of Richmond, | Oct., 1880, | 8 | 0 | 0 | July, 1879, | 8 | 3 | 52 |
| Gallia, | May, 1879, | 7 | 22 | 50 | May, 1881, | 7 | 18 | 50 |
| Arizona, | Sep., 1881, | 7 | 8 | 32 | Sep., 1881, | 7 | 7 | 48 |
When the success of vessels of the size of the Arizona and the Gallia was made apparent, it was decided by the Cunard Company to build a larger and faster ship than previous ones. Accordingly, in the autumn of 1880, specifications were issued to some of the leading shipbuilding firms, asking them to tender for the construction of a vessel of 500 feet in length, 50 feet beam, and 40 feet depth. At the suggestion of Messrs J. & G. Thomson, who were successful in securing the contract for this remarkable vessel, the dimensions were increased to 530 feet by 52 feet by 44 feet 9 inches. With these dimensions, and with mild steel as the constructive material, the new vessel—the Servia—was thereafter proceeded with in Messrs Thomson’s establishment.
The Guion line, not to be left behind, placed the order for a vessel of the dimensions first proposed for the Servia, with Messrs John Elder & Co., but, in order to be faster than the Servia, the weight-carrying was considerably reduced, and the boiler power much increased. The wisdom of this step has been justified by the now generally received opinion that these fast steamers should not carry such heavy cargoes as the slower ones. This new vessel for the Guion line was the Alaska, now justly noted for her fast runs across the Atlantic.
The Inman Company also decided not to lag behind, and as soon as the conditions of the design of the Servia had been fixed, they placed the order for a ship—the City of Rome—with the Barrow Shipbuilding Company, intended to be larger, finer, and faster. Expectations as to speed and carrying powers were not in her case fulfilled, and the result of the dissatisfaction which this occasioned, was, that the City of Rome changed ownership, Messrs Henderson Brothers, of Anchor Line fame, coming into possession. In the hands of its new owners, the City of Rome was re-arranged internally, and her boiler power was considerably augmented, while her engines also were thoroughly revised. When first built, the vessel was fitted with engines of 8500 horse-power. As revised, they indicate 12,000 the acquisition being largely due to the fitting of four additional boilers. The results which have accrued from the extensive alterations made are such as to have firmly established the vessel in a foremost place in the Atlantic service.
The performances of the vessels named have been the subject of considerable interest to all concerned in shipping affairs, and to the public generally. The following table of fast passages accomplished during the past two years by these vessels has been compiled from published records, and from information supplied by the shipowning companies:—
| Names of Vessels. | Out. | Home. | ||||||
|---|---|---|---|---|---|---|---|---|
| Date. | Time. | Date. | Time. | |||||
| D. | H. | M. | D. | H. | M. | |||
| Alaska, | April, 1882, | 7 | 4 | 32 | June, 1882, | 6 | 22 | 0 |
| Do., | May, 1882, | 7 | 7 | 0 | Sep., 1882, | 6 | 21 | 48 |
| Do., | May, 1882, | 7 | 4 | 10 | Jan., 1883, | 6 | 23 | 42 |
| Servia, | Jan., 1882, | 7 | 8 | 13 | —— | —— | ||
| Do., | Aug., 1883, | 7 | 6 | 0 | —— | —— | ||
| City of Rome, | May, 1883, | 7 | 12 | 16 | June, 1883, | 7 | 7 | 4 |
| Do., | June, 1883, | 7 | 4 | 56 | July, 1883, | 7 | 2 | 19 |
| Do., | Aug., 1883, | 6 | 22 | 6 | Aug., 1883, | 6 | 21 | 4 |
| Do., | Sep., 1883, | 7 | 3 | 0 | Sep., 1883, | 6 | 23 | 24 |
An addition to the list of competitors was made in the Aurania, built by Messrs Thomson in 1882, and tried in June, 1883, when she attained a mean speed of 17¾ knots, and showed herself not unequal to a maximum speed of 18½ knots under circumstances ordinarily favourable. An untoward and serious accident to her machinery laid the Aurania aside just as her capabilities in actual service were being shown. It is during the “passenger season” that the qualities of these transatlantic steamers are best brought out, and it remains with the season which has just begun, to demonstrate to the full the Aurania’s powers.
A similar remark applies to the Oregon, a still more recent competitor from the same stocks as the Alaska, whose dimensions correspond with those of the Alaska, except in respect to breadth, the first-named vessel having 3-ft. 6-in. more beam than the latter, the figures being—length over all, 520-ft.; breadth, 54-ft.; depth, 40-ft. 9-in. Extra power of engines to the extent of nearly 3000 horses indicated has been fitted in the Oregon. On the occasion of her speed trial on the Clyde she ran the distance between Ailsa Craig and Cumbrae Head—-29½ nautical miles—in 1 hour 20 minutes, or about equal to 20 knots per hour. This was attained with the engines indicating 12,382 horse-power and making 62 revolutions per minute, the steam pressure being 110-lbs. per square inch. This result was doubtless attained under conditions more favourable to speed than the vessel is, as a rule, likely to meet with in actual service; and, as has been indicated, it still remains with the future to determine how far the aims of the owners and builders of the Oregon are realised.[1]
In the America, launched from the yard of Messrs J. & G. Thomson, near the close of 1883, and presently being fitted for sea, the National Steamship Company (Limited), of Liverpool, have embodied the results of their careful study of the development and changes in the mode of conducting the American trade. From such experiments—for they can hardly be considered anything else—as the rapid passages of the Alaska, the City of Rome, and other “greyhounds of the Atlantic,” the company see it is no longer possible or profitable to have “composite” vessels—i.e., those intended to carry a large cargo as well as passengers,—but that practically one class of vessels must be built for the passenger traffic and another for the conveyance of cargo. The vessel represents an attempt to solve the problem of producing a ship which shall have large passenger accommodation and a high speed, with a comparatively small first cost and a reasonable consumption of coal. She is built of steel, and of the following dimensions:—Length, 440 feet; breadth, 51¼ feet; depth of hold, 36 feet; gross tonnage, about 6,000 tons. Her engines are of the inverted three-cylinder type, the high pressure cylinder being 63-ins. diameter, the two low pressure cylinders being 91-ins. each, while the piston stroke is 66-ins. Six double ended boilers and one single ended, having in all 39 furnaces, are fitted. The power expected to be developed is about 9,000 indicated. The speed guaranteed by the builders of the America is 18 knots an hour, and confidence is entertained by all concerned as to this result being attained.[2]
It is abundantly evident, notwithstanding what has already been achieved, that the brisk competition among transatlantic companies for the “fastest steamer afloat” has not yet exhausted itself. The determination some time ago publicly expressed by Mr John Burns, the able chairman of the Cunard Company, to maintain a leading position, has since taken decidedly active shape in the contract entered into and now being carried out by Messrs John Elder & Co.: that is, the construction of the two huge and powerful steamers of unprecedented speed, already referred to near the beginning of this work. They are each of 8000 tons burthen, 500 feet in length, 57 feet broad, by 40 feet depth of hold. Engines of 13,000 horse-power will be provided, which, it is computed, will drive the vessels at a speed of 19 knots an hour. With the establishment of these remarkable steamships in this most important service, the prospect is near of a transatlantic passage lasting only six days, if not indeed considerably under that period.
Communication with our South African colonies is another service in which modern progress, as regards high speed, has been conspicuously manifest. The steamers engaged in this service—belonging to the Union Steamship Coy. and Messrs Donald Currie & Co.—had special attention directed towards their powers as to fast steaming were exerted to the utmost them during the Zulu War of 1879, at which juncture in the transport of our soldiery. In the autumn of 1878 the Pretoria, belonging to the Union Coy., made the outward passage to the Cape, via Maderia, in 18 days, 16 hours, including 4½ hours detention. The passage home was made in the autumn of 1879 by the same vessel in 18 days, 13¼ hours, including about 5¾ hours stoppages. These passages are fairly representative of the best performances of the vessels engaged in this service, and they have not since been much excelled. In midsummer, 1880, the Durban, another of the Union Line vessels, accomplished the homeward run via Maderia in 18 days, 9 hours, including about 6½ hours stoppages. The Drummond Castle, belonging to Messrs Donald Currie & Co.’s Castle Packet line, has made the homeward run in 18 days, 18 hours, or, excluding detentions, in 18 days, 13 hours. The Hawarden Castle, of the same line, has made the fastest outward run on record. In the autumn of 1883 she accomplished it in 18 days, 15 hours, including five hours detention at Maderia, leaving the actual steaming time 18 days, 10 hours. The distance traversed by vessels on this service is some 6,000 miles, and the average speed attained is about 13 knots per hour. In the case of one of the Union Coy.’s vessels, the average speed attained has been as high as 13·8 knots per hour over the greater portion of the voyage, the indicated horse-power developed being about 2,570, and the consumpt of coal about 52½ tons per day. For a considerable time recently the Companies have found it more remunerative to drive their vessels at moderate speed, but in times of emergency, such as the outbreak of hostilities in our colonies, their qualities as transports traversing long distances at high speed are eminently efficient.
The employment of steamships in long voyages and at high rates of speed, for which, not so long ago, it was generally supposed sailing ships were only adapted, has been eminently successful. By the opening of the Suez Canal the passage to China was shortened from about 13,500 miles to about 9800 miles, that to India from over 10,000 miles to 6000. Although steamers were running to China via the Cape of Good Hope, before the opening of the Canal, and doing the service most admirably, it is subsequent to that great change, and indeed quite recently that the most noteworthy advances have been made in shortening the time occupied on these important services. The passage is now made by steamers under ordinary circumstances in less than thirty days, which sailing ships under the most favourable conditions took three and a half to four months to accomplish. The average speed attained by the steamers prior to the short route never exceeded ten knots; steamers now frequently average twelve knots over the whole distance, except during their passage through the Canal.
The Stirling Castle, built in 1882 by Messrs Elder & Co., for Messrs Skinner & Co.’s China fleet, attained a speed of 18·4 knots on her official trial. During 1883 she proved herself to be the fleetest vessel ever engaged in the China tea-carrying trade, arriving in the Thames several days ahead of the China mails, although the latter came part of the way overland. The run from Woosung to London was made in 27 days 4 hours steaming time. Other vessels belonging to this Company, and vessels of the other lines on this important service, although not equalling the performances of the Stirling Castle, are exemplifying almost daily the immense superiority of steamers over sailing ships for regularity and despatch in long passages.
As the distance to Australia—i.e., some 12,000 miles as ordinarily taken—is only about 900 miles less via the Suez Canal than by the Cape of Good Hope, steamers are employed on both routes. On the 12th May, 1875, the St. Osyth left Plymouth for Melbourne via the Cape, called at St. Vincent for coal, and thence steamed continuously to Melbourne, reaching her destination on the 27th June. Her full steaming time was about 43½ days, the average speed attained being over 11½ knots per hour. This passage, although considered most remarkable at the time, has since been surpassed. The Lusitania, of the Orient line, in 1877 made the passage to Melbourne in 40¼ days, including a detention of 1¼ days at St. Vincent while coaling. Her actual steaming time was almost exactly 39 days, her average speed being only a trifle under 13 knots. The Cuzco, of the same line, during the summer of 1879, made the homeward passage from Adelaide to Plymouth in 37 days 11 hours, including all detentions. In the Orient, which was the first vessel specially designed and constructed for the Australian direct steam service, a most noteworthy step in advance was made. She was launched in September, 1879, from the yard of Messrs Elder & Co., and on her completion was tried for speed, when she attained a maximum average speed of 17 knots per hour. She has made the passage from Plymouth to Adelaide, via Suez Canal, in 35 days 16 hours, and the same voyage via Cape of Good Hope in 34 days, 1 hour, steaming time.
| Length, | 455 ft. 0 in. | Depth, | 37 ft. 0 in. |
| Breadth, | 48 ft. 0 in. | Tonnage (Gross), | 5,588 tons. |
| Built by Messrs Elder & Co., 1881. | |||
The Orient was followed in 1882 by the magnificent Austral, whose high promise was suddenly blighted for a time by an unfortunate accident. While coaling at her moorings in Sydney harbour by night, the water was allowed to flow into the ship through her after coal ports, carelessly left open and unwatched, and she thus gradually filled, and sank to the bottom. She has since been raised, brought home, and restored to her pristine splendour. She is presently engaged in the express service of the Anchor Line between Liverpool and New York, her performances being such as should gratify all concerned. The Austral on her trial attained a speed of 17·3 knots, and has made the passage from Plymouth to Melbourne, via the Suez Canal, in the unprecedented time of 32 days, 14 hours steaming.
Until quite recently the only direct communication with New Zealand has been by sailing vessels, but the New Zealand Shipping Company (Limited) and the Shaw, Savill, & Albion Company (Limited) are at the present moment in the thick of organising monthly services of high-class modern steamships to the Antipodes. The former Company in 1883 despatched the Ionic, which they had chartered, with other of the White Star steamships, for the purpose. This vessel made the passage out to New Zealand in 43 days, and home in 45 days, including stoppage for coaling. Passages of a similar character have been made by this vessel and others of the Company’s own fleet, three of which—the Tongariro, Aorangi, and Ruapehu—are splendid new steel vessels from the stocks of the famous Fairfield yard. The vessel last named has just made the passage home from Lyttelton, New Zealand, to Plymouth, in the marvellously short period of 37 days, 20 hours, 40 minutes, steaming time; the time, with detentions, being about 39 days. The other Company referred to are having two magnificent steel vessels built by Messrs Denny & Bros., of Dumbarton, to be named the Arawa and Tainui, each of 5000 tons gross. These vessels are to maintain a sea speed of 12½ knots, the engines to be fitted representing a noteworthy advance in the line of economical consumpt of fuel with prolonged terms of steaming.
Between 1875 and 1882 the number of steamers having ocean speeds of 13 knots and upwards, increased from twenty-five to sixty-five. Of these there were only ten—previous to 1875—of 14 knots speed and upwards, whereas at the beginning of 1882 there were twenty-five of this character. During the years 1882 and 1883 alone the increase in the number of such vessels has been almost double that for the previous period named. The highest speed previous to 1875 did not exceed 15 knots, now there are numerous vessels with speeds exceeding 17 knots, several even approaching 18 knots, while in one or two cases the speed attained—under favourable circumstances probably—is stated to have been considerably over 18 knots, the Guion Liner Oregon, indeed, reaching the round figure of 20 knots.
Viewed purely from the point of view of the sea voyager, such results are alike remarkable and gratifying, whilst considered in their technical and commercial aspects they also call for admiration. It is questioned, however, whether in most cases the attainment of great speed has been accompanied with corresponding or proportionate advance in other matters with which vital progress is concerned. Commercially, it is of the utmost importance that increase of speed and power should be achieved, with the least possible weight of machinery, water, and fuel to be carried; with the least possible expenditure of fuel; with safety and efficiency in working; with low wear and tear, and cheapness of maintenance.
The efficiency of the ship and machinery in fulfilling the various and often conflicting conditions of economical service is a matter with which the naval architect and the marine engineer have jointly to deal. Where the conditions cannot all be equally satisfied, it is the province of these two to make that sort of compromise which gives the best results in each special case. In cargo-carrying vessels, for example, an economy in the consumption of fuel may often be the dominant and regulating quality. An economy of one-fourth of a pound per horse-power per hour gives, on a large transatlantic steamer, a saving of about 100 tons of coal for a single voyage. To this saving of cost is to be added the gain in wages and sustenance of the labour required to handle that coal, and the gain by 100 tons of freight carried in place of the coal. Again, it is estimated that every ton of dead-weight capacity is worth on an average £10 per annum as earning freight. Supposing, therefore, the weight of machinery and water in any ordinary vessel to be 300 tons, and that by careful design and judicious use of materials the engineer can reduce it by 100 tons without increasing the cost of working, he makes the vessel worth £1,000 per annum more to her owners. To these and other such considerations, which often influence the naval architect and engineer in their designs, and due regard to one or more of which not infrequently prevents the attainment of all-round success, should be added many others concerned with the after-management of vessels. For example, the length of voyage to be performed, the seasons and the markets in particular trades, the number of ports of call, and the coaling facilities at each, are all matters which must be taken into consideration when measuring, from one standpoint or from particular instances, the degree of success attained in general.
The diminution in coal consumpt, coincident with the increase of steam pressure and the acceleration in speed which has been attained in recent years measures the principal element of progress. In many of the “racers” of recent times, it is true, speed is attained at what may appear a great sacrifice of fuel, but these are cases in which the commercial considerations often used to measure the efficiency of ordinary cargo-carrying steamers are not applicable. Owners—of transatlantic steamships especially—realise from experience that “speed pays,” and they find it of more advantage to ensure certainty of arrival at the port of destination than to save a few tons of coals on the voyage.
During the past sixteen years or so the advance made in respect to the reduced ratio of fuel consumed to power developed has indeed been considerable. Before the period stated a vessel of say 700 tons carrying capability was not only much slower than the present-day vessels but the coal supply amounted to about 16 tons per day of 24 hours, whereas vessels are now being built of like size which attain an average speed of 9 knots, the consumpt of coal not being more than 6 tons per day. In 1872 the consumption of coal in vessels whose engines were worked at a pressure of from 45-lbs. to 65-lbs. per inch (the latter being then the highest pressure recorded), did not exceed 2½-lbs. per indicated horse-power per hour. This indicated an improvement in the marine engine during the previous decade, represented by a reduction in the consumpt of fuel by more than one-half the amount previously thought indispensable. Since 1872, there has been a further reduction in the average consumpt of fuel to the extent of 15 or 16 per cent., or in the average from 2⅛-lbs. to less than 1¾-lbs. per indicated horse-power per hour.
As in the case of the vessels themselves, mild steel is largely taking the place of iron in the construction of marine boilers. The change has reduced the weight of this important item of machinery by about one-tenth, a great advantage in itself, as increasing the dead-weight capability of the vessel. The questions as to the reliable character of the boilers made of steel with respect to strength under working, and as regards corrosion, are being practically answered as time goes on; and, as in the case of ship structure, in a way very satisfactory for the new material. There is every probability that a further advance may soon be made in connection with marine boilers, in the way of constructing the shell in solid rings, thus doing away with the longitudinal seams. The strength of boilers is of course governed by the strength of the seam, and this is never above 75 per cent. of the solid plate. Hence, if solid shells are employed, an increase in pressure of about 25 per cent., with the same thickness of shell, may be obtained. Appliances are now being laid down in the Vulcan Steel and Forge Coy., Barrow-in-Furness, for this purpose.
Improved appliances and modes of construction, no less than the change of material employed, have played a large part in rendering the boilers of modern steamships capable of being worked at the higher pressures now common. It is not possible, however, with the space at command, to treat of these; nor is it practicable to consider or even enumerate all the various improved fittings which in the aggregate so materially enhance the efficiency of boilers.
One such feature particularly noteworthy because of the success with which it has been applied to the boilers of very many modern high-class merchant ships may be shortly referred to. This is the corrugated mild steel furnace, manufactured by the Leeds Forge Company on Mr Samson Fox’s patent, an illustration of which is given in Fig. 4. This shows a single corrugated furnace flue, flanged at the end to meet the tube plate of the boiler. The strength of these flues to resist collapse has been proved in the presence of the officials of the Admiralty, Board of Trade, and Lloyd’s Register, to be, on the average, four times greater than a plain flue of the same dimensions. An immediate effect of this has been to increase their average diameter from 3-ft. to 4-ft., the thickness of plate-½-inch—remaining the same; a result as to diameter and thickness quite impracticable with ordinary furnaces. Some have even been made to carry 170-lbs. per square inch of steam pressure, 4-ft. 8-ins. outside diameter constructed of one single plate, with the weld so arranged as to be below the fire bars in the furnace.
By the corrugated, as against the plain tube, a greatly increased heating surface is presented to the flame and the heated gases of the furnace, thus yielding a greatly enhanced evaporative power, equal to at least 50 per cent. more than in the ordinary form. Better allowance is made by the corrugated surface for the expansion and contraction caused by changes of temperature in the furnace, without in any way impairing its efficiency as a longitudinal stay for the boiler. Through the increased diameters and the augmented surface possible by these corrugated tubes, their adoption lessens the number of furnaces and stokers necessary for the horse-power required. As a further consequence, the boiler space may be diminished, and an increase effected in the cargo space or freight-carrying capacity of the vessel.
The advantages of corrugated flues as compared with plain flues cannot all be named, but the extraordinary extent to which they are now employed in the best class of steamships is the best proof of their superiority. It is stated that if the flues which have been made by the Company since their introduction about the beginning of 1878, and are now at work, were placed in one continuous line, they would extend to a length of over twenty miles, representing, in marine and other engines, nearly one million horse-power.
The number of separate types of boilers introduced into steamships has been much increased of recent years—an evidence that engineers are growingly conscious of the possibilities which may result from improved efficiency in this agent of propulsion. One direction in which their efforts at present are being largely put forth, is that of securing the more complete combustion of fuel in the furnaces. Considerable success has already attended the working of boilers under forced draught, or the admission of air to the furnaces under pressure. Combined with special types of boilers, it has been affirmed that nearly 50 per cent. more power has been obtained by this means. There is doubtless much to be expected from this system in the future, especially as it may be associated with a change in the form or type of boilers by which the number and weight of such items will be reduced. The saving of space in the vessel, the economy in consumption of coal, the reduction in dead-weight of machinery, are possibilities of the movement now in progress which cannot fail to effect materially the commercial character of our high-class mail and passenger steamships, and merchant vessels generally.
Other directions in which advance has been made during the period under review are, considerably higher steam pressures, less heating surface, and smaller cylinders, for indicated horse-power developed. The various improvements in design and construction which have contributed to these results cannot be entered into with any degree of fulness here. For detailed treatment of these matters, readers are referred to the papers read by eminent engineering authorities, before the various professional and scientific institutions, a list of which papers follows the present chapter.[3]
Reduction in the weight of machinery per indicated horse-power developed is, in general terms, the common line in which engineering effort lies, and in which no little advance has lately been made. Every possible opportunity of using steel, where it can be introduced with safety and efficiency, has been taken advantage of. Hollow crank steel shafts and propeller shafting in place of solid shafting; propellers and pistons of cast steel in place of iron; and boilers of mild steel plates, are a few of the directions in which large weight-savings have been effected. That there is still great room for improvement in this direction is shown by the following statement, given by Mr F. C. Marshall, of Messrs R. & W. Hawthorn, Newcastle-on-Tyne, in his valuable paper read before the Institution of Mechanical Engineers in 1883. The figures given show for various classes of vessels the average weight of machinery per indicated horse-power, in steamships of the merchant marine—and for comparison—of the Royal Navy:—
| Lbs. per I.H.P. | |
|---|---|
| Merchant Steamers, | 480 |
| Royal Navy, | 360 |
| Royal Navy, fast cruiser Iris, | 280 |
| Torpedo Ram, Polyphemus, | 180 |
| Torpedo vessels, | 60 |
| Ordinary marine boilers, including water, | 196 |
| Locomotive boilers, including water, | 60 |
The figures given are for weights of machinery, including engines, boilers, water, and all fittings ready for sea.
One of the most important of recent advances in marine engineering—affording as it does the means of using higher steam pressures than have hitherto been used with economy—is the introduction of the triple expansion description of engines already referred to. This important departure was begun in 1874, when Mr A. C. Kirk, of Messrs R. Napier & Sons, designed and fitted on board the screw-steamer Propontis, built for Mr W. H. Dixon, of Liverpool, by Messrs Elder & Co.—with whom Mr Kirk at that time was engineering manager—engines involving the principle of triple expansion and abnormally high pressure of steam. In 1877 the principle received further practical development on board the Isa, a pleasure yacht fitted with triple expansion engines, designed in 1876 by Mr Alexander Taylor, consulting engineer of Newcastle-on-Tyne, who has subsequently designed several other engines of the same type for larger merchant steamers.
As not infrequently happens in connection with inventions, several minds were occupied, and independent ideas matured almost simultaneously, in the matter of triple expansion engines. Mr Kirk had secured the patent for engines involving this principle subsequent to, but before he was made cognisant of, Mr Taylor’s work. At the same time he learned that in quite another quarter the designs for such a type of engine had already been perfected. Mr Kirk, on hearing these facts, relinquished the patent rights he had secured. Notwithstanding this, it is to the success of the engines designed by Mr Kirk, and fitted by his firm on board the screw-steamer Aberdeen, that the recent development of the system is largely due. This vessel was built in 1881 for the Australian service of Messrs G. Thomson & Co., London and Aberdeen, and measures 350 feet by 44 feet by 33 feet. Her engines work at a boiler pressure of 125 lbs. per square inch. The three cylinders are respectively 30 inches, 45 inches, and 70 inches in diameter, and the stroke is 4 feet 6 inches. The smallest is the high pressure cylinder, into which the steam is first admitted; from thence it passes, after expansion, into the second or intermediate cylinder; after still further expansion it passes into the third or low pressure cylinder, from whence, after the expansion is completed, it is discharged into the condenser.
When the Aberdeen was completed, 2,000 tons of dead-weight were put on board, and the consumption was tested on a four hours’ run at 1,800 horse-power. The result was the consumption at the rate of 1.28-lbs. per indicated horse-power per hour, with Penrikyber Welsh coal. From this the designer of the engine inferred a sea consumption of good Welsh coal at the rate of 1·5 to 1·6-lbs. per indicated horse-power. The maximum measured mile speed was 13·74 knots, with 2,631 indicated horse-power, and a consumption of 1 ton 17 cwt. per hour. The vessel started from Plymouth on 1st April, 1881, upon her first voyage to Melbourne, with 4000 tons of coals and cargo—weight and measurement—on board. She arrived at Cape Town on the 23rd April, having accomplished the distance—5,890 miles—in 22 days. After taking in about 140 tons of coal, she left for Melbourne on the 24th, and arrived there on the 14th May, in 20 days. The whole time occupied in steaming from Plymouth to Melbourne was, therefore, 42 days. Her average indicated horse-power on the voyage has been about 1,880, and the consumption less than thirty-four tons per day, or at the rate of about 1·69-lbs. per indicated horse-power over the whole voyage. Since these results were obtained, Messrs Napier have fitted three sets of 5000 H.P. triple expansion engines into vessels built for the Compania Transatlantica Mexicana, and are completing a duplicate of the Aberdeen.
The firm of Messrs Denny & Coy., Dumbarton, are at present making engines of the triple expansion type for the new steamers of the Shaw, Savill & Albion Company’s direct New Zealand service. There are four cylinders and two cranks, the cylinders being arranged in pairs, tandem fashion, the small on the top of the large. Expansion takes place in three stages, the first small cylinder taking steam from the boilers about five-eights of the stroke, and expanding into the valve chest of the second small cylinder, where it is further expanded. From thence it exhausts into the valve chest common to both the large cylinders described. The steam to be supplied to these engines is to have a pressure of 160-lbs. per square inch, the highest yet carried in marine engines. These instances of actual advancement, taken in conjunction with the favourable light in which the triple expansion principle is regarded by our foremost marine engineers, augur well for the future of steamship propulsion.
The activity characterising merchant ship construction, and especially the enormous increase in their dimensions and speed within recent years, have necessarily led to speculation with regard to what form the ship of the future will take. There have not been wanting, indeed, actual propositions and elaborately prepared designs of what the ideal ship should be. A company was sometime ago formed in Washington, U.S., to have three vessels built of a novel type, the patented invention of Captain Lundborg, a Swedish engineer, intended to make the Atlantic passage in five days. It was also announced that the order for their construction had actually been given out, but this is wanting in confirmation. Great expectations were entertained in America regarding what was termed the dome-ship Meteor, built on the Hudson in the early part of 1883 from the designs of Captain Bleven. A company had been formed under the designation of the “American Quick Transit Company,” the chief supporters being Boston merchants, to build several large steamships on the proposed lines, but the utter failure of the Meteor to answer the promises of her inventor has relegated the scheme to the vast limbo of unfulfilled American projects. Three years ago or more, scientific journals gave publicity to a scheme of “Ocean Palace” steamship, patented by Mr Robert Wilcox, of Melbourne, Victoria, the claims for which ranked themselves under the heads of speed, safety, and comfort. Double hulls, as in the case of some Channel steamers, were employed, but each of the hulls was divided into two cigar-shaped portions, thus giving to the submerged whole, a quadruplicate character, and which, with its palatial superstructure, was apt to remind one—shall it be said?—of Rome and her seven hills, or Venice and her island base! The design, nevertheless, was to give the least resistance with the greatest buoyancy and stability. The method of propulsion proposed by Mr Wilcox was also novel. He placed a couple of enormous drums fore and aft (between the hulls), which were to be driven by the engines as if they were paddle-wheels. Over these drums was placed a continuous band of iron links, upon which, at suitable intervals, paddles or blades were fixed. A comparatively low speed of engine was to give a high speed of velocity to this band of blades; and as there would be twenty-one paddles, all immersed at the same time, their grip of the water was to be such that there should be little slip. Whether on a serious application of the principles involved in this invention to a ship for the Australian service the voyage would have been made, as was claimed, in 26 days, equal to an increase in speed of 75 per cent., has never of course been determined! Still another scheme, and one which the inventor has been encouraged to prosecute by the recommendations of eminent authorities on both sides of the Atlantic, is that of Captain Coppin, noted for his success in salvage operations, which consists of an “Ocean Ferry” partaking as to form somewhat of the features above described for Mr Wilcox’s “Ocean Palace.” The speed said to be possible by Captain Coppin’s vessel is twenty knots an hour, and the terminal ports proposed are Milford Haven and New York. It was announced some time ago that M. Raoul Pictet, the eminent engineer of Geneva, was engaged upon the question of ship design and propulsion, and was in hopes that by application of his ideas he might yet send ships careering over the sea at the rate of thirty-seven miles an hour!
Enough has been said to show that there is no lack of inventive effort being put forth towards a realization of the ideal ships of the future. In a service, however, like that of the Atlantic, where competition is strong and keen, and where the monetary issues are neatly adjusted between rival companies, there is little chance of any of the various projects being tried. An impression exists among shipowners—for which doubtless there are sufficient grounds—that time and capital staked on novelties or “new departures” are simply invitations to defeat in the race or to absolute ruin itself. This commercial prudence and industrial caution has been startled in several ways of recent years—e.g., by meteoric flashes such as the Livadia and Meteor—the ultimate effect of which has been to illumine and make clearer the probable line of advancement.
By pretty general consent of those most competent to judge the ships of the immediate future will possess the broad distinctions of being either purely passenger or purely cargo-carrying mediums. It is equally agreed that twin in place of single screw propellers will be employed, and that for the express ships nothing less than 20 knots per hour will be considered satisfactory. On a subject, however, concerned not with historical facts, but with theories and scientific forecasts, it may be well not to enlarge, especially as the future is evidently charged with possibilities of which present-day designers can have but indefinite notions. The subject of employing electrical energy as the propulsive power on board ship is at the present time engaging serious attention, but the degree of practical and commercial success attained does not, as yet, warrant any anticipation of its immediate application to vessels beyond small craft, such as launches and ferries. In the midst, however, of such immense and marvellous works achieved by this great—and, in some senses, modern—force, it would be both idle and unwise to keep out of view the possibilities of its future as affecting ship propulsion.
List of Papers and Lectures bearing on the speed and propulsive power of modern steamships, to which readers desiring fuller acquaintance with the technique and details of the subject are referred:—