As in making the Clyde a navigable river there were many eminent names, connected with the works, brought forward from time to time, so in the special and leading industries on its banks, both in ship-building and engineering, there are many names which have become household words, and will be honoured in the future as in the past.

Henry Bell, whose monument stands beside the old fort of Dunglass, overlooking the river which his enterprize has rendered famous amongst the rivers of the world as the cradle of European steam navigation, started his Comet in 1812. Bell was a clever, enterprising man, and appears early to have turned his attention to steamship propulsion, as in 1800 he tried some experiments in this direction, and in the same year laid his plans before the Admiralty, but without a successful issue. Lord Nelson, however, thought differently, and with a deeper insight into the future than his colleagues, said: , My Lords and gentlemen, if you do not adopt Mr. Bell’s scheme other nations will, and in the end vex every vein of this empire. It will succeed, and you should encourage Mr. Bell.” The practical success was indeed very soon shown in America, where Fulton, with a native-built boat and a Boulton .fc Watt engine, started the Claremont on the Hudson, and it was not till about five years later that Bell managed to get his long-cherished scheme accomplished.

The Comet, begun in 1811, and launched in 1812, has several well-known names associated with her, as she was built by John Wood, of Port-Glasgow, “the father of all that is best in the style of our ships, and truest in the practical application of science in the ship-building trade of Great Britain.” David Napier, afterwards so celebrated in connection with the development of the steamship industry of the Clyde, made the boiler. Bell’s Comet, after undergoing various changes, His wrecked off Craignish, on the west coast, in October, 1820, and the engine was afterwards recovered and finally placed in the Museum at South Kensington, London. Bell was on board the Comet at the time of the disaster, as lie had gone especially with the view of getting subscribers for a bigger and more powerful boat. This was now gone into vigorously, the West Highland lairds coming forward readily, and in 1821 Comet No. 2 appeared, which, after plying for some time to Inverness, was sunk by collision with the steamer Ayr, off Gourock, on 20th October, 1S25; upwards of seventy people were lost in this disaster. The vessel was afterwards raised and many valuable articles recovered.

Henry Bell was born at Torphichen Mill, near Linlithgow, on the 7th of April, 17G7; he died at Helensburgh on the 14th November, 1830, and was buried in the churchyard of Row, in the neighbourhood.

That the early attempt by Bell had all the elements of after success in it, appears from the following statement drawn up by well-known early Clyde engineers:

“Glasgow, 2nd April, 1825.

“We, the undersigned engineers in Glasgow, having been employed for some time past in making machines for steam vessels on the Clyde, certify that the principles of the machinery and paddles used by Henry Bell in his steamboat the Comet in 1812, have undergone little or no alteration, notwithstanding several attempts of ingenious persons to improve them.

Signed by Hugh and Robert Baird, John Neilson, David and Robert Napier, David M‘Arthur, Claud Girdwood & Coy., Murdoch & Cross, William M'Andrew, William Watson.”

Professor Rankine also remarks, in speaking of this introduction of steam power: “Since that period the advancement of steam navigation has consisted not so much in the development of new principles, as in the improvement of workmanship, arrangement, and economy of fuel, and the progressive increase of the size, power, and speed of steamships, and the extent of their voyages.” The whole subject of the introduction and development of steam propulsion is one of great general interest, as illustrating the application of mechanical skill and inventive genius in overcoming difficulties; yet, in any general account of the progress from the early periods until now (as the field is so wide and the interval of time great since the first feeble attempts were made on inland rivers to use the power of steam), we lose the more salient points in the development because of the wide-spreading results with which we are at the present day so familiar. For the last half-century we have been living in an age of steam. In 1705, James Watt, while repairing a model of a Newcomen engine belonging to the natural philosophy class of the University of Glasgow, made his discovery of the separate condenser. This afterwards, applied practically with many other beautiful mechanical inventions, gave vigour to a machine which formerly, from its elementary form and rude construction, had been limited to the pumping of water. Although Watt made his discovery in 17G5, it was not till the year 1781 that we find him writing: “Our rotative engines, which we have now rendered very complete, are certainly very applicable to the driving of cotton mills, in every case where the convcniency of placing the mill in a town, or ready-built manufactory, will compensate for the expense of coals and of our premiums.”

As yet the steam-engine was on its trial, and encountered great opposition ere it won its way by sheer force of applicability to the many operations gradually opening up. In reference to the great invention of James Watt, the late Professor Macquorn Rankine says: “Watt set to work scientifically from the first. Tie studied the laws of pressure of elastic fluids, and of the evaporating action of heat, so far as they were known in his time; he ascertained as accurately as he could, with the means of experimenting at his disposal, the expenditure of fuel in evaporating a given quantity of water, and the relations between the temperature, pressure, and volume of steam. Then, reasoning from the data which he had thus obtained, he framed a body of principles expressing the conditions of the efficient and economic working of the steam engine, which are embodied in an invention described by himself in the following words, in the specification of his patent of 1769: “‘My method of lessening the consumption of steam, and consequently fuel, in fire engines, consists of the following principles:

“‘Firstly, that vessel in which the powers of steam are to be employed to work the engine, which is called the cylinder in common fire-engines, and which I call the steam-vessel, must, during the whole time the engine is at work, be kept as hot as the steam that enters it; first, by inclosing it in a case of wood or any other materials that transmit heat slowly; secondly, by surrounding it with steam or other heated bodies; and thirdly, by suffering neither water or any other substance colder than the steam to enter or touch it during that time.

“‘Secondly, in engines that are to be worked wholly or partially by condensation of steam, the steam is to be condensed in vessels distinct from the steam-vessels or cylinders, although occasionally communicating with them. These vessels T call condensers; and whilst the engines are working, these condensers ought at least to be kept as cold as the air in the neighbourhood of the engines by application of water or other cold bodies.

“‘Thirdly, whatever air or other elastic vapour is not condensed by the cold of the condenser, and may impede the working of the engine, is to be drawn out of the steam-vessels or condensers by means of pumps, wrought by the engines themselves or otherwise.

"'Fourthly, I intend, in many cases, to employ the expansive force of steam to press on the pistons, or whatever may be used instead of them, in the same manner in which the pressure of the atmosphere is now employed in common fire-engines. In cases where cold water cannot be had in plenty the engines may be wrought by this force of steam only, by discharging the steam into the air after it has done its office.

Lastly, instead of using water to render the pistons and other parts of the engines air and steam tight, I employ oils, wax, resinous bodies, fat of animals, quicksilver, and other metals in their fluid state.’ ”

The earlier forms of the Watt engine had wooden “walking-beams.” An example of such an engine may be seen near the Museum in the Kelviimrove Park of Glasgow, where it was re-erected some years ago. Iron was afterwards substituted for the wooden beam, and so designed as to give a maximum of strength, to resist the heavy strains coming upon it, with a minimum of weight. The Blam-engine still holds its place as a reliable engine for mill work, and the Americans have retained it for their steamers at least on the eastern waters and coasts. Watt’s prolific brain thought out from time to time many important inventions which proved useful in the development of the steam-engine.

In 1812 we start with the Come I, and by 1811 we have in all seven steamers which had been built up to that year, including the Industry, which, as the seventh steamer built on the Clyde, is, as already stated, still in existence at the age of seventy-four, lying rotting away in Bowling Harbour (see cut on p. 229). In 1820 we find the number of steamers as given in the Steamboat Companion for that year plying on the Clyde to be twenty-four, nine of which (including the first Comet) extended their voyages to Fort-William, Campbeltown, Belfast, and Liverpool. In 1828 the number, according to Dr. Cleland, extended to fifty-nine, twenty-five of which were sea-going boats; Liverpool and Dublin being, however, as yet the farthest ports ventured to. In 1836, another step of eight years, we find recorded in Fowler's

Commercial Directory for Renfrewshire seventy-eight steamers as calling at Greenock, of which thirty-one were for Liverpool, Dublin, Belfast, and generally ports beyond the end of the firth. The voyages of the Sirius and Great Western to New York in 1838 and the establishment of the Cunard Co. in 1840 brings us to the period of ocean-going steamers, and the interest in the river and coasting boats built or plyiug on the Clyde ceases to have a paramount interest.

The engine of the Comet1 was of a somewhat peculiar form, called a bell-crank arrangement, and, like a number of the earlier engines, was connected to the paddle-wheels by spur gearing. Afterwards the side-lever engine was commonly employed in sea-going vessels, and the steeple and oscillating engine on river boats. The custom in this country at least was to work the steam at low pressure with the aid of the condenser. In some cases, however, high-pressure steam was used; but its progress was checked by the disastrous explosions which occurred, notably in the case of the Telegraph at Helensburgh and the Cricket on the Thames. Broadly speaking we had at first a period of wooden boats, bluft-bowed and broad in proportion to length, driven more or loss by side-lever engines, the propellers being paddle-wheels with fixed fioats. A single long narrow funned rose abaft the paddle-box, and the vessels were heavily sparred and rigged. Copper boilers in many cases were used, and steam pressures of from 5 to 10 lbs. were common. The jet condenser was in use, and the steam, when unused, was blown from a steam-pipe led up alongside the funnel with a roaring noise. By a simple arrangement it can now quietly escape into the water. The regulating of the escape in the old boats was managed through a safety-valve loaded with a series of discshaped weights, which could be adjusted on the spindle of the safety-valve, placed upon the steam-chest, immediately adjoining the funnel, and manipulated from the deck by a stoker or attendant engineer.

The use of iron for shipbuilding did not become general till about thirty-five years after the Comet was launched. Some early attempts are recorded to have been made with canal boats both in England and Scotland. John Wilkinson, of Lancaster, about the year 1750 made an iron boat, and in 1787 another was tried on one of the Staffordshire canals. In 1818 an iron boat named the Vulcan (designed by Sir John Robinson, of Edinburgh, in 1816) was built at Faskine, on the Monkland Canal, by Thomas Wilson. This boat plied for a number of years on the Forth and Clyde Canal. Wood has now almost disappeared as a building material for our vessels; but on the Continent fully one-half of the vessels are still built of that material.

The great drawback to the use of steam of a high pressure in these times was the weakness of the boiler. Watt from the first clearly saw the advantages in economy which would arise from its use, but was unable, from the imperfect mechanical appliances of his time, to obtain the necessary resisting strength in the material employed.

In a few years after Bell’s Comet a goodly number of steamers were plying on the Clyde, Built and cngined by different constructors; some of these men ultimately rose to much distinction. The name of Jas. Cook early appears as the engineer for several of the early boats; thus the next steamer after the launch of the first Comet was the Elizabeth, started on 9th of March, 1813. It was engined by James Cook of Tradeston, as were a number of others later on. David Napier is specially connected with the sea-going vessels, as in 1818 the Bob Boy was cngined by him with a single side-lever engine, a type much developed in later years. This vessel was built by William Denny of Dumbarton, and thus we find a well-known name on the Clyde appearing amongst the early builders of our sea-going vessels. This same builder’s name, however, appears as early as 1814, when he built the river boats Trusty and Marjery. The Bob Boy plied to Belfast, and was afterwards on the Dover and Calais route. In 1817 Mr. Napier, like Mr. Seath at a later date, tried the running of a steamer above the bridges.

The name of Robert Napier, however, is linked to others who took a leading part in the development of ocean-going steamers. We find the history of events bringing us in contact with great commercial undertakings, and one more especially where the Clyde and the Mersey in some measure joined hands. In 1824 the firm of Messrs. G. & J. Burns was started, their vessels plying to the North of Ireland. In 1828 they built their first steamer for the Liverpool traffic. Mr. Napier became early associated with these movements, and thus we find that in 1840, when the Cunard Co. was established, and in the formation of which the Messrs. Burns and Mr. Napier took a leading part, his engines were placed in the first steamer of the company, and the steamers themselves were all built on the Clyde by such well-known firms as those of Duncan, Wood, and Steele.

In connection with this it is interesting to notice that the four vessels with which the Cunard Coy. started in the Liverpool and American service in 1840, viz. the Britannia, Acadia, Caledonia, and Columbia, all wooden paddle boats of about 1100 tons burthen each, have been year by year added to until the total number of boats used since that time amounts to fifty-nine. After passing through the period of iron, with paddle or screw, they are now built of steel, with screw-propellers, such ships as the Umbria and Etruria being of about 8000 tons burthen. The large paddle ships culminated in the Scotia, also built for tho Cuuard Co. by R. Napier & Sons in 1861. The dimensions of this boat were: Lenoth, 366 feet; breadth, 47 feet 6 inches; tonnage, 4050. She had two side-lever engines of a nominal horse-power of 1000. The diameter of the cylinder was 100 inches; stroke, 12 feet. The paddle-wheels were 40 feet diameter, and the size of the floats 11 feet 6 inches by 2 feet. Time of passage to New York, 9 days. This, the last paddle steamer of the Cunard Co., was a very different vessel from their first steamer the Britannia, no doubt considered a wonderful boat in her day. The side-lever type of engine is illustrated by the figure on p. 211, which shows the engine of the Industry, and also the spur-wheel connection used in the older boats.

The first iron steam-vessel was the Aaron Manby, made at “Horsely” in 1821, and put together at London. This vessel plied on the Seine. The first iron steamer built on the Clyde was the Aglaia in 1827. This vessel plied on Loch Eck. The first iron steamer to ply on the Clyde was the Fairy Queen, built in Glasgow at the Old Basin, about a mile and a half from the river, to which she was carried, and launched in 1831. This vessel plied to Largs about 1836. The Vanguard was the first iron vessel built by R. Napier at Govaij (1843). She plied for many years on the Glasgow and Dublin route.

The use. of wood, however, continued for many years, all the early Atlantic steamers being built of this material; and it was not till 1856, when the Persia was added to the celebrated Cunard fleet, that that company introduced iron for the hulls of their vessels. The firm of Tod & M‘Gregor is associated with the first iron seagoing steamer, the Royal Sovereign, built in 1839. She was engined by this firm and plied to Liverpool. The firm of T. Wingate & Co. had the special honour of having made the engines of the first steamer which crossed the Atlantic from Britain, the Sirius, built in 1837 by Menzies & Sons, of Leith. The engines were of the side-lever class, and had the special feature of being fitted with Hall’s Surface Condenser. The name of Caird & Co., of Greenock, is specially associated with the start of the deep-sea boats belonging to the firm of Messrs. G. & J. Burns, as in 1828 they cngined the Glasgow for that company. The engines were side-levers, the steam pressure being 5 lbs. per square inch. TheLiverpool, a bigger ship than the Glasgoiv, was added to the same company’s fleet in 1830, and was built by Steele & Co. of Greenock. The Atrato for the West India Royal Mail Steam-Packet Co. was built and engined by Caird Co., at Greenock, in 1854. Dimensions: 315 feet long by 42 feet broad, and 26 feet 6 inches deep; gross tonnage, 3466; diameter of cylinder, 96 inches; stroke, 9 feet; nominal horse-power, 800. The paddle-wheels had feathering floats. The average ocean speed was 13'3 knots, with an average daily coal consumpt of 100 tons. The Atrato was an iron vessel.

Experiments were being made from time to time with the screw-propeller, early attempts being made with a screw or helix of several turns. Stevens, at New York, tried a small vessel on the Hudson in 1802. The cumne and propeller can still be seen at the Stevens’ Institute, Hoboken. The engine is placed vertically, and geared by a spur-wheel to the propeller shaft. Smith and Woodcroft in this country, and Ericsson in America, also tried various arrangements; and in 1840 the late Captain Kincaid of Greenock tried a four-bladed propel lei In a steam-boat on the Forth and Clyde Canal. But previously to that, and as early as 1828, Captain Kincaid made a wooden four-bladed propeller, and experimented with it 011 a long-boat in inid-occan. The actual propeller then used is now in the Kelvingrove Museum. The first British steamer fitted with a screw-propeller was the Archimedes, 237 tons, and built on the Thames in 1839. This vessel appears to have come up to Glasgow on a trip. The first screw-ship in H.M. navy was the Dwarf, an iron vessel, built in 1843.

The Great Britain, built in 1843, was the largest vessel of that day. It may be interesting to state some particulars of this ship as noted at the time,1 as she was a departure in several ways from what had gone before, both in size and method of propulsion. In the journal referred to we find amongst other details that “ the Great Britain is no doubt an object of great interest; she differs from every other steamer which has ever crossed the Atlantic; she is the largest—she is built of iron—and she is propelled by the screw instead of paddles. She is thus destined to test three principles:— The first as respects size. The advantage of iron over wood as a material for marine architecture may already be considered as established; but the trial of the Screw v. Paddle is yet pending for want of sufficient evidence.” The Great Britain still, or until recently, running, after nearly half a century’s service, was designed by Brunei, and built at Bristol. She was launched after some difficulty, on account of her unprecedented size, in 1843. From an advertisement notifying her sale in 1881, the dimensions are given as—length, 274-2 feet, or 322 feet over all; breadth, 48‘2 feet; depth, 3T5 feet; 3270 gross tonnage. Engines by J. Penn & Sons, Greenwich; and boilers by Fawcett, Preston & Co., Liverpool. Strongly built of Low Moor iron of the finest quality. This vessel plied with much satisfaction in the Australian % trade. The propeller was 16 feet diameter; the main shaft was hollow, measuring 28 inches diameter outside and 10 inches inside: this part being bored out and a stream of water sent through it to keep the bearings cool. The engines were geared to the shaft. The Great Britain, like the Great Eastern, made her first trips across to New York, the passage being fifteen days. In one of her outward trips, by a mistake as to the lights, she got ashore in Dundrum Bay on the Irish coast, and lay there for a considerable time. This event, occurring to this wonderful ship of the time, was reckoned sufficiently notable to be illustrated in one of the views of a panorama which came to Glasgow after the mishap; the describer carefully pointing out to the spectators the position of the “propeller,” which could be easily seen, as the vessel was shown at low-water, pretty much high and dry.

Shortly after this, in 1845, the first iron screw-steamer, the Fire Queen, was built at Glasgow; and in 1850, the City of Glasgow, of 1001 tons, commenced to ply between Glasgow and New York. This vessel was built by Tod & M'Gregor, and was an iron screw-steamer of 1600 tons, measuring 227 feet long by 82 feet 7 inches broad, and 24 feet 7 inches deep. She had two geared beam-cngines of 880 horse-power; the propeller was 14 feet diameter.

The City of Glasgow left Glasgow on the 16th of April, 1850, and arrived in New York on the 8d of May, after a passage of 16 days 21 hours. She encountered head winds ; her greatest day’s run was 241 knots. The return voyage was made in 14 days 6 hours; greatest day’s run, 203 knots.

Attempts were made from time to time to increase the effective action of the paddle-wheel, the feathering float being the most important improvement. (See cut p. 21C.)

The Glasgow, which followed her, was the first steamer belonging to the Inman Company, so long well-known on the Atlantic route for its swift and commodious steamers. This company, under the new designation of the Inman and International Company, are at present having two very large Atlantic liners built and engined on the Clyde by Messrs. J. & G. Thomson, Clydebank; twin-screws of about 10,000 tons, with corresponding power and equipment.

The Glasgow left Glasgow for New York on 16th September, 1857, and arrived on the 30th of the same month; the greatest day’s run was 254 knots. She left,New York on the 11th and arrived in the Clyde on the 28th October; greatest day’s run, 262 knots.

The dimensions of the City of New York now launched are: length on water-line, 525 feet; breadth, 63£ feet; depth, moulded, 42 feet; tonnage, 10,500. This vessel is fitted with twin-screws and triple expansion engines.

The Collins line, belonging to the United States, started in 1850, and continued to run for about ten years; their vessels were large paddle-wheel steamers.

It is just about thirty years since the iron vessel and screw-propeller may be said to have taken a prominent place in the history of naval architecture. About the time of the introduction of the screw-propeller for oceangoing vessels it was thought hy some that a modified application might prove commercially successful; and this gave rise to auxiliary screw-propellers, the idea being to aid the force of the wind upon the sails by means of steam-power applied to a screw-propeller. To test the correctness of this, a vessel was built at Liverpool in 1846, called the Sarah Sands, of 1100 tons, and made several voyages between that port and New York, her passages occupying about seventeen days. This vessel was nearly destroyed by fire in the Indian Ocean while conveying troops during the Indian mutiny. For the following incidents the author is indebted to one of the passengers:—The vessel sailed from Portsmouth on 15th August, 1857, having on board 350 officers and men of the 54th Regiment; on the 11th November lire broke out, and raged so furiously that it was only through the military discipline that it was got under; to add to the danger, during the conflagration some powder exploded in the after-part of the ship. The women and children were placed in boats and rafts which lay alongside. The iron got white-hot, and the masts went overboard, but finally the fire was extinguished and some sail got up. The boats lying around were then taken in. They had been followed by shoals of sharks, which had been attracted by the light and the prospect of making the castaways their prey. The chronometer was lost, and the watches of the officers were used instead. A course was set for the nearest land, the Mauritius, 1000 miles distant, and the weather fortunately remaining fine, the battered craft and miserable-looking ship’s company arrived safely on the 23d November.

Another incident of the sea may be mentioned in connection with the Three Bells, built at Dumbarton by Messrs. Win. Denny Brothers in 1851. She was the largest iron sailing ship afloat at the time, and during one of her voyages came upon the San Francisco, a United States transport, which had a number of troops on board. As this vessel was in a sinking condition the captain of the Three Bellsdetermined to stand by them till morning, so that help might be given, which incident has been described by the poet Whittier in the following lines:

“Beneath the low-hung night cloud
That raked her splintering mast
Tlie good ship settled slowly,
The cruel leak gained fast.

“A voice came down the wild wind,
‘IIo! Ship ahoy! ’ its cry :
Our stout Three Bells of Glasgow
Shall lay till daylight by!’

“All night across the waters
The tossing lights shone clear;
All night from reeling tatl'rail
The Three Bells sent her cheer.

“And when the dreary watches
Of storm and darkness passed,
Just as the wreck lurched under,
All souls were saved at last.”

The firm of Randolph & Elder is inseparably associated with the successful introduction of the compound engine, as that of R. Napier & Sons is now with the triple-expansion system. In a memoir of John Elder, by the late Professor Macquorn Rankine, we find that Elder mastered the subject of reduction of friction by neutralizing the forces which drive the shaft. In 1853 they patented vertical direct-acting and geared compound engines for driving a screw-propeller; in 185G, two opposite cranks; in 1858, three cranks. The first vessel fitted with a compound engine by Randolph, Elder, & Co. was the Brandon in 1854, the consumpt of coal obtained being 3^ lbs. per indicated horse-power per hour; formerly this consumpt had been as high as 4 to 41, lbs.

After this the Pacific Steam Navigation Company got two paddle steamers built—the Inca and Valparaiso. These were fitted with Randolph & Elder’s compound engines in 1856, the consumpt being from 2½ to 3 lbs., “a degree of economy never before realized in marine engines; and this was not only obtained on the trial trips, but maintained during many years’ subsequent service at sea. It amounted to a saving of from 30 to 40 pel cent of the coal previously burned by steamers of the same class.” This great reduction of fuel now made long ocean passages commercially practicable.

In the Memorials of James Watt, published in 1856, it is stated that “at that time by far the largest proportion of steam-vessels launched in the Clyde are of iron,” and “of the whole steam-vessels constructed on the Clyde, or in progress at the various building-yards in 1852, amounting in all to 73, only four were of wood; while the proportion of screws to paddle-wheels was as 43 to 30.” TheTimes, treating of shipbuilding in 1883, says: “One fact, emphasized by the returns for the year under review, is, that wood has practically, if not absolutely, gone out of existence as a shipbuilding material. Iron is now the general material of which vessels are constructed, though steel is year by year coming to the front. This is particularly shown in the returns from the Clyde. Very few years have elapsed since the first steel ship was launched on the Clyde. Four years ago the entire output of steel vessels was 18,000 tons. In 1882 the quantity had been increased to fully 100,000, and in 1883 it rose to 120,000 tons, or nearly one-third of the whole tonnage launched, the proximity of steel-plate works, and the distance of the source of part of the supply of iron plates undoubtedly contributing to that change. In the north-east ports the number of steel vessels built is much fewer. On the Tyne 12 vessels have been built of steel, and on the Wear 4. But in the Scotch and Irish ports this material is being increasingly used, and in addition to the Clyde, Grangemouth and Belfast have used it largely. Another fact prominently brought out is that sailing are speedily giving way to steam-vessels. Of the 32G vessels launched on the Clyde during the year, 240 are steam and only 8G sailing. On the Tyne not one sailing vessel has been built, and on the Wear one only. Taken all round, the size of the vessels has increased. The Clyde still holds its own for vessels of the largest class; but taking an average between large and small, the Tyne and Wear show larger figures than the Clyde. Boughly stated, the average is as follows:— Clyde-built vessels, 1210; Tyne, 1400; Wear, 1G85.”

The most of our great ocean liners of the present day are built of steel. This material, both in ship plates, angles, &c., and in boiler plates, has within the last few years largely replaced the use of wrought iron,—partly due to its greater strength, whereby less material is required; a very great advantage, when we consider the great weight of the vessels and boilers of the present day. The use of steel for shipbuilding is not, however, altogether new, as, about twenty-five years ago, some river steamers were built on the Clyde of that material.

Mr. Robert Duncan, speaking on the classification of shipping, gives the following statistics of the comparative.

The consumpt of coal in all the earlier sea-going steamers was excessive, consequently the available space for merchandise was very limited, giving rise to the belief expressed at the time of the first ocean passages, that it would be impossible to carry on a commercially successful traffic with steam. In reference to this, Sir William Pearce, Bart., in a lecture delivered in 1881, points out that thePersia burned 6’3 tons of coal for every ton of cargo she carried; whilst the Gallia, built in 1879, and fitted with screw-propeller and compound engines, burned only about half a ton of coal for every ton of cargo, and, besides, carried this cargo about two and a half knots faster. Still further, the Arizona, also built in 1879, burns only 5 cwts. of coal for every ton of cargo carried. The daily coal consumpt in the Persia was 150 tons per day, the indicated power 8600, or 3'7 lbs. of coal per indicated horse-power. In the Gallia the daily consumpt was 97 tons, the indicated power 5000, or 1/8 lbs. per indicated horse-power per hour. In the Arizona the daily consumpt was about 110 tons or P75 lbs. per I.H.P. The speeds of the Persia, Gallia, number of vessels built at ports in Great Britain in 1886:—

In connection with the subject of the size of our future sea-going steam-vessels, Mr. William Denny says (Watt Lecture, 1882): “Steamers were increasing in size, and the least costly increase for weight-carrying, and, up to certain points, for speed, was in beam, provided sufficient draughts could be obtained. Steamers would follow their natural course of development, and it would be for dock proprietors, river trustees, and harbour boards to see that their docks, rivers, and harbours were of such depth as to permit them to favour steamers so developed. He believed it was found daily more difficult to build the larger types of Atlantic steamers rigid enough for the service, even with the great percentage of their displacement devoted to structural weight. A reaction would set in against their extreme proportions and absolute length. When that happened, beam would be increased; as a consequence draught increased, and distinct preferences accorded to ports having great draught of water. Besides, great draught of water, and comparative shortness of a steamer, were more favourable to the efficiency of the screw, by keeping it well immersed, than great length with shallow draught, which told very much against the screw’s efficiency.” Mr. Denny further states that he he is “ convinced that the steamer which was to do the Atlantic work would be a vessel of what might be called at the present time moderate length. That was a vessel which would not only be shorter than the City of Rome, but shorter than the Servia, and shorter than the Alaska, which, of the three steamers, as far as he could learn, came nearest the type he had in view. He believed the steamer to do this work would he under 500 feet in length between perpendiculars. What her other dimensions should be would have to be fixed by experiment and a very careful series of calculations.”

The annexed diagram of the comparative sizes of some leading steam vessels was originally used to illustrate a lecture delivered by the author during the Naval Exhibition, held in Glasgow in 1880-81, under the auspices of the city authorities.

The compound engine, as introduced on the Clyde by Randolph, Elder & Co., in the first mercantile steamer fitted with this form of engine, the Ihxmdoii, in 1854, reduced the consumpt of fuel to a large extent, later on, due to further improvements, such as surface condensation, the use of three cylinders instead of two, wherehy the efforts on the shaft were more completely equalized, the consumpt was further reduced, until, in the latest compound engines, less than 2 lbs. of coal were required. Recently the triple-expansion engine has been introduced, whereby a further saving in coal is obtained. In this form of engine the expansive action of the steam is carried out through three cylinders consecutively—that is, it is admitted from the boiler into the first and smallest cylinder and, after driving the piston of that cylinder before it for a part of the stroke, the admission of the steam is cut off, the rest of the stroke being accomplished by the expansion of the steam already admitted. Thereafter this steam passes into the next or intermediate cylinder, and presses forward the piston in that cylinder, and finally, as its expansive power is not yet exhausted, it is allowed to enter the third cylinder, pressing forward in turn the piston there. The-intensity of the pressure, as it enters the second or intermediate cylinder, is much less than when entering the first; hut as this cylinder is made proportionately wider, and has therefore a greater area of piston, the total driving power on the piston is still obtained about equal to that in the first cylinder. The third cylinder is in turn larger than the second cylinder. Certain proportions have been adopted as best suited to equalize the pressures on the pistons, and from thence to the cranks.

The quadruple-expansion engine, of which a few have been made, is simply, like the triple-expansion engine, a development of the compound—that is to say, in the compound the steam was expanded through two cylinders, in the triple through three, and in the quadruple through four, higher pressures being required in the triple and quadruple forms than in the compound, as the range of expansion is greater. Here, however, we touch the main item in the increased economy of the later forms, and which may be shortly referred to.

Generally speaking, steam when expanding may lie represented as following what is known as Boyle’s law of gaseous expansion—that is, that the pressure varies inversely as the volume; so that if, in the triple-expansion engine above referred to, we suppose that the steam is cut off from the boiler after driving the piston through half of the stroke, or when one-half of the cylinder is full, then at the end of the stroke the volume of steam will be double of what it was when cut off. The pressure, therefore, will be only one-half of what it was before being cut off—that is to say, the volume having doubled, the pressure has fallen to one-half. In like manner, when the volume has further increased—say to five times—then the pressure will be reduced to one-fifth. It will now be found that the mean pressure is higher when the expansion is considerable, in proportion to the steam used. Thus, if the steam were not used expansively at all the pressure would be uniform throughout the stroke; but a whole cylinder full of steam would be used. If cut off at say half-stroke, the mean pressure would now be approximately seven-eighths of what it was in the first case. But only one-half of the steam is now used.

It is, therefore, economical to use the expansive force of the steam; and to do this with the greatest effect a long cylinder or a series of cylinders is necessary. It is also necessary that the initial pressure be high, so as to take advantage of expansion to the fullest.

In the compound system, therefore, an advantage is gained; and in the triple and quadruple systems a still further improvement arises from the use of steam at a higher pressure and expanded more fully, whereby less steam can be made to give a better mean result. A saving is thus effected, both in coal consumed and in boiler space. Pressures have now reached 160 lbs. and  170 lbs. per square inch, and will, no doubt, go higher still. The limit of economical working cannot, however, be far off, as with increased pressure difficulties will be met from the greater heat of the steam affecting the working parts.

The whole question of economical working, in a word, depends upon the amount of effective work which can be obtained from the coal consumed. So that, not only is the engine subject to further improvement, but also the boiler and furnace. Combustion by forced draught, &c., are all elements in the question. From the combustion of 1 lb. of coal about 14,500 thermal units should be obtained. Roughly speaking, this energy may be stated to be expended as follows:—In the triple-expansion engines as now used at sea, we may take 1 lb. of coal consumed per hour as equivalent to one horse-power; but as one horse-power rcpresentl 33,000 foot-pounds of work done per minute, then the total work done by the combustion of the If lb. of coal in the hour is 33,000 x 00 = 1,980,000 foot-pounds. But it can be shown that from the combustion of one pound of coal 14,500 thermal units should be obtained, and consequently from I f lb. 21,750 thermal units, which, multiplied by 772 (the mechanical equivalent of heat), gives 10,791,000 foot-pounds of work done in the hour; if, therefore, we compare the work actually done with the work which should be done if all the coal energy could be converted into useful work by the engine, we have this ratio:

The triple-expansion system of marine engines was first tried in the Propontis, built in 1874, by Messrs. J. Elder. The diameters of the cylinders were 23, 41, and 62 inches respectively; steam pressure 150 lbs. Mr. William Parker1 says: “The first engines made for sea-going purposes on the triple-expansion principle were those made in 1874, from the designs of Mr. A. C. Kirk, now of the firm of Messrs. R. Napier & Sons, for the S.S. Propontis. The next triple-expansion engines were those of the yacht Isa, of Newcastle-on-Tyne, in 1877, steam-power 120 lbs. In 1881 the Aberdeen was built and fitted with tripleexpansion engines by Messrs. R. Napier & Sons, the steam pressure being 125 lbs. In the Propontis and Aberdeen there were three cranks, in the Isa two cranks only, two of the cylinders being arranged tandem-wise. The diameters of the Aberdeen s cylinders are 30, 45, and 70 inches respectively, with 4 feet 6 inch stroke.” Since then many sets of such engines have been made, the steam pressure rising to 160 and 170 lbs. A few quadruple-expansion engines have also been made.