The application of steam-power to navigation is one of the most wonderful triumphs of human ingenuity. By this power vessels of gigantic size are impelled across the trackless ocean; and, in spite of its storms and resisting tides, establish a chain of communication between the shores of the remotest regions, as safe and as certain as if connecting the cities of a continent. Thirty years have scarcely yet elapsed since the first steam-ship of traffic was launched on the Hudson; and now there is hardly a navigable river or an inland lake whose waters are not agitated by the steam-boat paddle, and its atmosphere darkened by her smoke; while even the ocean itself is crossed in almost every direction by lines of steam-ships of immense size, and of beautiful construction. Many individuals have claimed the merit of inventing an art so pregnant with interest to mankind; and almost every civilized country contends for the honour of its birthplace. If the mere suggestion of the application of steam-power to the purposes of navigation entitle an individual to the credit of having invented the art, there are, doubtless, many who may be regarded as its inventors; for this suggestion was repeatedly made almost as early as the invention of the steam-pump, although from the nature of steam machinery, then and for long after, no advantage could be derived from it.

To show how the ingenious of that time were led to propose steam as a motive power in navigation, we shall give a brief account of the contrivances which had been devised for the propulsion of vessels.

The substitution of other apparatus than oars, and of other power than human labour, to impel vessels in a calm or against the wind, is of unknown antiquity. The Egyptians are said to have used, in their boats, wheels like the paddle-wheels of the present day, but moved by oxen working in a gin on the deck of the vessel. Valerius, in his treatise De Re Militari, gives an account of paddle-wheel boats used by the Romans as transports, the paddle-wheels being driven by men or by horses; and we have, from many sources, abundant evidence of the existence of similar boats elsewhere. In a book published in London in 1578, called Inventions and Devices, by William Bourne, we find the following passage: "And furthermore, you may make a boat to go without oars or sail, by the placing of certain

1 For these historical notices, ending in p. 693, we are not indebted to the same contributor who wrote the rest of the article. Na-by a motion derived from the piston-rod of his engine, to impel the paddles of a boat. Here, with the discovery of the high-pressure engine within his reach, Papin relinquished his experiments; and Newcomen, adopting his cylinder and piston, and Savary's mode of condensation, a few years afterwards completed the atmospheric engine. The difficulty of converting the reciprocating motion of the atmospheric engine into a rotatory motion was the great bar to the use of it in any other way than for pumping water. Yet not a few speculators are to be found at this time inventing other means of propelling vessels than by paddle-wheels, so as to take advantage of the single reciprocating action of the engine. In 1730, Dr John Allen proposed to give motion to vessels by forcibly ejecting a stream of water or current of air from their stern; a scheme which, since his time, has been again and again invented, patented, and abandoned. Seven years after his proposal, Jonathan Halls published an account of a steam-boat invented by him. In this boat, he had two paddle-wheels suspended in a frame projecting from its stern. In the body of the boat were two atmospheric engine cylinders with their pistons: to each piston one end of a rope was fastened; the rope was then carried round a pulley on the corresponding paddle- wheel, and one end was allowed to hang free, with a weight attached to it. When one of the pistons was pressed down in its cylinder by the weight of the atmos- phere it pulled its rope, and, consequently, moved round the paddle-wheel in a degree due to the length of the stroke and the diameter of the pulley. While the piston was ascending in the cylinder, on the admission of the steam, the counterbalance weight, at the outer end of the rope, dragged round the pulley in the contrary direc- tion; but the pulley being attached to the paddle-wheel by a ratchet-wheel, the latter remained stationary during the retrograde motion of the former. There being two cylinders and two paddle-wheels in the boat, it was so ordered that one should be in motion while the other re- mained stationary, and that thus the boat's motion should be continuous. However ingenious this plan of a steam- boat may be, we find no evidence that it was ever re- duced to practice; but in a tract which Halls published in 1737, he meets, and combats in a most masterly man- ner, every objection which he conceives might be urged against his project.

In 1757, the celebrated Daniel Bernoulli, in an essay which obtained a prize from the Academy of Sciences, after demonstrating the effect of many mechanical con- trivances which might be substituted for oars in moving vessels, suggests paddle-wheels moved by steam-power or the force of gunpowder. Another of the essayists, Gautier, a canon of Nancy, in suggesting the same me- chanism and the same power, shows very great fertility of invention, and skilful application of mechanical re- sources in the adaptation of the different parts of the machinery.

In 1759, Mr J. A. Genevois, a minister of Berne, invented a species of propellers, which, like a duck foot, would expand, and present a large surface to the water when moved against it, but would fold up into small compass when moved in an opposite direction. It is scarcely necessary to say, that these duck feet oars failed; but it is a melancholy fact, that similar apparatus has been frequently re-invented since the days of the

* A Description and Draught of a new invented Machine for Carrying Vessels or Ships out of, or into, any Harbour, Port, or River against Wind and Tide, or in a Calm; for which his Majesty has granted Letters Patent, for the sole benefit of the author, for the space of fourteen years. By Jonathan Halls. London, 1737, 12mo.

pastor of Berne, and with the same degree of practical Steam-Na- vigation.

The Comte d'Auxiron, in 1774, under the auspices of a company formed for the purpose, made some expe- riments with steam-boats on the Seine. These unfor- tunately failed; but M. J. C. Perier, who had been present, repeated them with improved machinery, a year or two later. His success was so indifferent as to offer no inducement to him to continue his experiments. It is unnecessary to swell the present work with examples such as these; and we shall therefore at once proceed to the time of Watt, whose labours gave to the steam- engine its power of almost universal applicability, and eminently fitted it for the moving of paddle-wheels.

Leaving undescribed the experiments of the Marquis de Jouffroy on the Seine in 1782, and the attempts of Runsey, of Fitch, and of Evans in America, between the years 1775 and 1787, which were attended with no beneficial effect, we proceed to notice the first attempts which were perfectly successful, and to which we more immediately owe the benefits of steam navigation. These were made in 1787, by a Scottish gentleman, Patrick Miller, Esq. of Dalswinton in Dumfries-shire, who, in that year, published an account of some experiments which he had made on the best mode of impelling single, double, and triple vessels, by the power of men and of horses applied to paddle-wheels. In this publication, Mr Miller states, "I have reason to believe that the power of the steam-engine may be applied to work the wheels, so as to give them quicker motion, and consequently to increase that of the ship. In the course of this summer I intend to make the experiment." He owed the suggestion of the steam-engine to a young man, Mr James Taylor, who resided in his family as tutor, and who had assisted him in his experiments; but neither Mr Miller nor Mr Taylor could devise a way of applying the engine to the boat. In this dilemma, Taylor suggested that they should have recourse to the aid of an old school-fellow of his, Mr William Symington, an engineer, at that time assiduously employed in endeavouring to adapt the steam- engine to wheel carriages. Mr Taylor seems to have sent an account of their project to Mr Symington, as we find the latter thus writing to the former, on the 20th August 1787: "I must make some remarks on your summer's inventions, which, if once made to perform what their author gives them out for, will undoubtedly be one of the greatest wonders hitherto presented to the world, besides its being of considerable emolument to the projector. Great success to you, although overturning my schemes." In the winter of the same year, Mr Miller was introduced to Mr Symington in Edinburgh, and saw the model of his locomotive carriage. Convinced of the perfect applicability of a similar engine to drive the paddle-wheels of a boat, Mr Miller gave orders for the construction of an engine on the same plan, under the direction of Symington and Taylor. The engine was accordingly made in Edinburgh, and sent to Dalswinton, and by them put together in October 1788. The en- gine, in a strong oak frame, was placed on one side of a twin or double pleasure boat on Dalswinton lake. The boiler was placed on the opposite side, and the paddle- wheels in the middle. In the middle of October, the machine was first put in motion; and the ingenious inven- tors had the gratification of witnessing the perfect suc- cess of the first steam-boat. Although the cylinders of the engine were but four inches in diameter, yet the boat attained a speed of five miles an hour. Mr Miller, anxious to try the experiment on a larger scale, commis- sioned Mr Symington to purchase a galert, or large boat at the Forth and Clyde Canal, and to get suitable engines Steam Navigation.

Every thing being completed, a trial took place on a level reach of the Canal, of about four miles in length, at Lock Sixteen. The trial was made in presence of many spectators, who were however disappointed in their expectations, owing to the breaking of the paddle-wheels. Stronger wheels were obtained, and another trial took place on the 26th December 1789, and the vessel moved at the rate of about seven miles an hour. Next day and afterwards the experiment was repeated with equal success; and the following account of it was transmitted by Lord Cullen to several of the Edinburgh newspapers:

"It is with great pleasure I inform you that the experiment which some time ago was made upon the great canal here by Mr Miller of Dalswinton, for ascertaining the powers of the steam-engine when applied to sailing, has lately been repeated with great success. Although these experiments have been conducted under a variety of disadvantages, and with a vessel built formerly for a different purpose, yet the velocity acquired was no less than from six and a half to seven miles an hour. This sufficiently shows that, with vessels properly constructed, a velocity of eight, nine, or even ten miles an hour may be easily accomplished, and the advantages of so great a velocity in rivers, straits, &c., and in cases of emergency, will be sufficiently evident, as there can be few winds, tides, or currents which can easily impede or resist it; and it must be evident that, even with slower motion, the utmost advantage must result to inland navigation."

It is much to be regretted that Mr Miller, having made so successful an experiment, carried his attempts no further. The boat was dismantled and laid up at Carron; and this ingenious and public-spirited gentleman directed his attention to other objects. His pursuits had a greater tendency to improve the condition of his country, than to enrich his own family.

In 1793, Rumsey, who, as we have already stated, had been unsuccessful in his experiments in America, got some American residents in London to defray the expenses of another experiment there. He, however, died before his boat was finished; and when it was got afloat by those engaged with him, it attained a speed of four miles an hour against wind and tide. The propulsion of this boat was effected, on the principle of Dr John Allen's, by ejecting a stream of water at the stern.

In 1795, Earl Stanhope revived the pastor of Berne's duct feet ears; but he could not cause his vessel to move at a higher rate than three miles an hour.

In the year 1801, Thomas Lord Dundas employed Mr Symington to make a tug-boat for dragging vessels on the canal. With this view, a series of experiments were made between 1801 and 1802, at a cost of £3000. In March 1802, Lord Dundas, Mr Speirs of Elderslie, and several other gentlemen, being on board of the newly-constructed tug-boat, which was named the Charlotte Dundas, it "took in drag," says Mr Symington, "two loaded vessels, each upwards of 70 tons burden, and with great ease carried them through the long reach of the Forth and Clyde Canal to Port Dundas, a distance of 19½ miles in six hours, although the whole time it blew a very strong breeze right ahead."

In consequence of an impression in the minds of some of the canal proprietors, that the paddle-wheels of the boat injured the banks of the canal, the project of the steam-tug was with great reluctance abandoned, and the boat was laid up in a creek of the canal, where it remained for many years exposed to public view. A year after this most successful experiment, Mr Fulton, an American, made a similar experiment on the Seine at Paris, under the auspices of the American chancellor, Mr Livingstone. Owing to a miscalculation of the strength of the boat, it had no sooner received the weight of the engine than it broke through the middle, and went to the bottom. Not disheartened, Fulton set about building a new vessel; and in August 1803 he launched it with its machinery. This vessel was 66 feet long and 8 feet wide; but moved so slowly, that we may describe the experiment as a failure. He afterwards came to Scotland, and saw Mr Symington's vessel. Of this visit, a memorial of Mr Symington's, which we have before quoted, gives the following account:—

"When engaged in these last experiments, I was called upon by Mr Fulton, who very politely made himself known, and candidly told me that he was lately from North America, and intended to return thither in a few months, but having heard of our steam-boat operations, could not think of leaving this country without first waiting upon me, in expectation of seeing the boat, and procuring such information regarding it as I might be pleased to communicate; he at the same time mentioned, however advantageous such invention might be to Great Britain, it would certainly become more so in North America, on account of the many extensive navigable rivers in that country; and as timber of the first quality, both for building the vessels, and also for fuel for the engine, could be purchased there at a small expense, he was decidedly of opinion it could hardly fail, in a few years, to become very beneficial to trade in that part of the world; and that his carrying the plan to North America could not turn out otherwise than to my advantage; as, if I inclined it, both the making and superintendence of such vessels would naturally fall upon me, provided my engagements with steam-boats at home did not occupy so much of my time as to prevent me from paying any attention to those which might afterwards be constructed abroad. Mr Fulton having thus spoken, in compliance with his most earnest request I caused the engine-fire to be lighted up, and in a short time thereafter put the steam-boat in motion, and carried him from Lock No. 16, where the boat then lay, four miles west the canal, and returned to the place of starting, in one hour and twenty minutes, to the great astonishment of Mr Fulton, and several gentlemen who at our outset chanced to come on board. During the above trip, Mr Fulton asked if I had any objections to his taking notes regarding the steam-boat; to which question I said, none, as I considered the more publicity that was given to any discovery intended for general good, so much the better; and having the privilege secured by letters patent, I was not afraid of his making any encroachment upon my right in the British dominions, though in the United States I was well aware I had no power of control. In consequence, he pulled out a memorandum-book, and, after putting several pointed questions respecting the general construction and effect of the machine, which I answered in a most explicit manner, he jotted down particularly every thing then described, with his own remarks upon the boat, while moving with him on board along the canal; but he seems to have been altogether forgetful of this, as, notwithstanding his fair promises, I never heard anything more of him, till reading in a newspaper an account of his death.

"From the above incontrovertible facts, which can be corroborated by a number of persons of respectability living at this day, it is very evident that commerce is not indebted to North America for the invention of steam-packets, it being hereby established beyond the possibility of doubt, to be truly British, both in the idea and practice; and that Mr Fulton's steam-vessel did not make its first appearance in the Hudson river earlier than 1806 or 1807, four years at least posterior to his having been on board the Charlotte Dundas steam-boat, and minutely examined it, when at work on the Forth and Clyde Canal, Fulton, having obtained what information he could, ordered, under an assumed name, it is said, a steam-engine from Bolton and Watt. He shortly afterwards returned to America, and in conjunction with Mr Livingstone obtained a patent, securing to them the prospective advantages of steam navigation in America, by what they rather insincerely termed their invention of steam-boats.

In 1806 Bolton and Watt's engine arrived, and in 1807 the first steam-vessel in America was launched on the Hudson river. It was called the Clermont, which was the name of Livingstone's residence. In spite of the advantages which it possessed over the Scottish vessels, in having better engines, and in its projectors having the benefit of Symington's experiments, it was a comparative failure, attaining at the utmost a speed of only five miles an hour.

The boat had not been long under weigh, on its first trip, when Fulton ordered the engine to be stopped. Having observed that the paddle-wheel floats were too deeply immersed in the water, he shifted them nearer to the centre of the paddle, so that they did not enter so deeply into the water; and this alteration had the effect of increasing the speed of the vessel.

Shortly after this first experiment, it was announced that the Clermont would sail from New York to Albany; and of this first voyage the following account was sent to the Editor of the American Citizen newspaper, by Fulton himself:

"Sir,—I arrived this afternoon, at four o'clock, in the steam-boat from Albany. As the success of my experiment gives me great hopes that such boats may be rendered of great importance to my country—to prevent erroneous opinions, and to give some satisfaction to the friends of useful improvements, you will have the goodness to publish the following statement of facts. I left New York on Monday at one o'clock, and arrived at Clermont, the seat of Chancellor Livingstone, at one o'clock: time, 24 hours; distance, 110 miles. On Wednesday I left the chancellor's at nine in the morning, and arrived at Albany at five in the afternoon: distance, 40 miles; time, 8 hours. The sum is 150 miles in 32 hours, equal to nearly 5 miles an hour, &c.—Robert Fulton."

During the same season, the boat made many voyages between New York and Albany, and in these she met with not a few accidents, arising chiefly from the defective construction of her paddle-wheels, which were of cast-iron, and had no support beyond the vessel. She was likewise injured by the sailing vessels, whose owners, dreading the intruder, ran them against her. The Clermont was at length laid up during the winter; and being enlarged and strengthened, she was again, in the spring of 1808, employed as a passage-boat between the same stations, and continued during the summer crowded with passengers. The success of their first vessel induced Messrs Livingstone and Fulton to build other two vessels, the Car of Neptune, of 300 tons, and the Paragon, of 350 tons.

Thus it was that steam navigation in America originated; and the enthusiastic and speculative Fulton enjoys the honour of having first shown to the world its commercial value. It is now proper time to mention that Fulton had been aided in his experiments on steam navigation by Mr Henry Bell, by whom the first steam passage vessel in Britain was constructed. The nature of this connexion will be better seen from Mr Bell's own account of it, which was addressed to the Editor of the Caledonian Mercury in 1816.

"Sir,—I observed in your paper lately a paragraph respecting steam-boats, in which the Americans claim the right to the discovery which is become of so much utility to the public. On this account I propose to give Steam Navigation a full statement of what I conceive to be the truth.

Mr Miller of Dalswinton first wrote upon the method of moving or impelling vessels or rafts through water by paddles, wrought by a capstan, or by the wind, in the manner of a wind-mill, which idea he afterwards gave to all the different courts in Europe. It will be recollected by most people in this country, that the French proposed to erect rafts for conveying troops to invade this country, by means of Mr Miller's wind-mill or capstan plan; for, it may be stated that this gentleman built two vessels at Leith, and put them in motion upon his new improvement, and even sent one of them to the King of Sweden as a present. After this, he thought that an engine could be so constructed as to be applied to work his machinery for the moving of his paddles; and accordingly he employed an engineer to put his plans in execution; but they failed for want of being properly executed. But to give you a more correct account of the manner Mr Fulton, the American engineer, came to the knowledge of steam-boats, that gentleman had occasion to write me about the plans of some machinery in this country, and beg the favour of me to call on Mr Miller of Dalswinton, and see how he had succeeded in his steam-boat plan; and if it answered the end, I was to send him a full drawing and description of it, along with my machinery. This led me to have a conversation with the late Mr Miller, and he gave me every information I could wish for at the time. I told him where, in my opinion, he had erred, and was misled by his engineer; and at the same time I told him, that I intended to give Mr Fulton my opinion on steam-boats. The friends of Mr Miller must have amongst their papers Mr Fulton's letter to me; for I left it with Mr Miller. Two years thereafter I had a letter from Mr Fulton, letting me know that he had constructed a steam-boat from the different drawings of the machinery I had sent him out, which was likely to answer the end, but required some improvement on it. This letter I sent to Mr Miller for his information, which must also be amongst his papers. This letter led me to think of the absurdity of writing my opinion to other countries, and not putting it in practice myself in my own country; and from these considerations I was roused to set on foot a steam-boat, for which I made a number of different models before I was satisfied. When I was convinced that they would answer the end, I contracted with Messrs John Wood and Company, ship-builders in Port-Glasgow, to build me a steam-vessel according to my plan, 40 feet keel, and 10 feet 6 inches beam, which I fitted up with an engine and paddles, and called her the Comet; because she was built and finished the year that a comet appeared in the north-west part of Scotland. This vessel is the first steam-boat built in Europe that answered the end, and is at this present time upon the best and simplest method of any of them; for a person sitting in the cabin will hardly hear the engine at work. She plies on the Frith of Forth betwixt the east end of the great canal and Newhaven, near Leith. The distance by water is 27 miles, which she performs, in ordinary weather, in $3\frac{1}{2}$ hours up, and the same down. There were many attempts to make steam-boats in this country before this one, but none of them ever answered the end; and even three years after the Comet was set a-sailing, there was a number of our first-rate engineers joined together, and obtained a patent for what they conceived a new discovery on the paddles for impelling the vessel forward. They were disappointed in their plan, and had to return to the model of the Comet."

The Comet was a vessel of about 25 tons, and her engine, which was a vertical one, exerted about three Steam Navigation.

Bell's success immediately excited conviction; and a vessel called the Elizabeth, 59 feet in deck, and with an engine of 8 horse power, was started by Mr John Thomson on the 9th of March 1815. The spirit of enterprise was now roused, and steam-boats rapidly succeeded each other, every succeeding one excelling its predecessor in power and beauty. No longer timidly confining themselves to the navigation of rivers, the projectors of those steam-ships boldly steered into the deep waters, crossing the channel between Great Britain and Ireland, and performing the dangerous coasting voyages between Glasgow and Liverpool, Leith and Aberdeen, and Leith and London.

The first person who ventured beyond the precincts of a river was in all probability R. L. Stevens of Hoboken. This gentleman had been associated with Chancellor Livingstone, previously to the connexion of the latter with Fulton, and had brought his experiments to a successful issue nearly as soon as Fulton and Livingstone. Fulton having, however, secured to himself the exclusive privilege of navigating by steam in the state of New York, Stevens at once conceived the bold idea of taking his vessel by sea from the Hudson to the Delaware. To Mr Stevens many of the improvements of steam navigation are to be ascribed. He introduced the modifications of Watt's engine, which we have represented in Fig. 2, p. 693, still in use in American vessels. He introduced engines of long stroke; and, as a necessary consequence, a long crank, and the further peculiarity of upright guides for the piston-rod, instead of the old parallel motion. To him we likewise owe the paddle-wheel with divided boards, by which the resistance of the water was rendered more uniform, and the concessions of the common paddle-wheels avoided. He improved the shape of the American steam-vessels, by substituting for the full round bows and sterns a fine entrance and a fine run. By this, and by making the length of his vessels eight or ten times their beam, he succeeded in raising their rate of sailing from nine to thirteen miles an hour.

Reverting to Britain, we find from the first introduction of Bell's Comet in 1813, steam navigation gradually improving as an art. The vessels were, however, of small dimensions, of low proportion of power, and of little speed, until the year 1818, when Mr David Napier directed his attention to the improvement of steam navigation. It is to this gentleman that Great Britain owes the introduction of deep sea communication by steam vessels, and the establishment of post-office steam-packets. In 1818, Mr Napier established between Greenock and Belfast a regular steam communication, by means of the Rob Roy, a vessel built by Mr William Denny of Dumbarton, of about 90 tons burden, and 30 horse power. For two winters she plied with perfect regularity and success between these ports, and was afterwards transferred to the English Channel, to serve as a packet-boat between Dover and Calais. Having thus ventured into the open sea, Mr Napier was not slow in extending his range. Soon after, Messrs Wood built for him the Talbot, of 120 tons. With two of Mr Napier's engines, each of thirty horse power, this vessel was in all respects the most perfect of her day, and was formed on a model which was long in being surpassed. She was the first vessel that plied between Holyhead and Dublin. About the same time he established the line of steam ships between the stations of Liverpool, Greenock, and Glasgow. For the traffic of these stations he built the Robert Bruce, of 150 tons, with two engines of 30 horse power each; the Superb, of 240 tons, with engines of 35 horse power each; the Eclipse, of 240 tons, with two engines of 30 horse power each. All these were established as regular deep sea traders before the year 1822, on a station which has not since been surpassed for the power, beauty, and speed of its steam vessels.

In 1822 was built by Messrs Wood on the Clyde, the James Watt steam-vessel, to ply between Leith and London. This vessel was of 448 tons measurement, and she carried two engines of fifty horse power each, made by Messrs Watt and Bolton, and completed entirely under the superintendence of Mr Brown of that firm. The James Watt was remarkable for having its paddles moved, not directly by the engine, but through the interposition of toothed wheels, so that the number of revolutions of the axis of the engine was greater than that of the paddles. With the exception of the low proportion of its power to its tonnage, the James Watt possesses almost all the qualities of the most improved vessels of the present day.

The next great advance in the art was made in 1828, when the first of the Leviathan class of steamers, the United Kingdom, was constructed. This steam-ship was 160 feet long, 26½ feet beam, and 200 horse power. She was built by Mr Steele of Greenock, and the engines were constructed by Mr Napier. Mr David Napier was also one of the first persons to introduce surface condensation in marine engines. He used it successfully in the Post-Boy, a steam-vessel built by him. The condenser was composed of a series of small copper tubes, through which the steam passed towards the air-pump; and, a constant current of cold water encircling the pipe, the steam was cooled and returned into water, which was again sent into the boiler for conversion into steam, without being mixed with the cold salt-water, which, in the usual plan, is injected into the condenser. But, like Watt, Cartwright, and others, who have tried this system both here and in America, he did not find the rapidity of condensation sufficiently great, and he returned to the old system of condensation by jet. Some years afterwards, however, he reverted to this system in peculiar circumstances which rendered it desirable; and, using flat plates instead of tubes, was again perfectly successful, and plied for years with no other condenser. But, like all the other cases where it has been introduced, the advantages of the system were not reckoned equivalent compensation for its disadvantages. The plan of condensation by tubes, again introduced at a recent date by Mr Hall, has been tried in numerous vessels, in some of which it has been abandoned, and in others it still continues to be employed.

The next change introduced very extensively into steam-vessels by Mr Napier, was the use of an upright or vertical steam-engine, or engine of direct connexion. The first engine of Bell was to some extent a vertical engine, inasmuch as the axis of the cylinder and of the crank were placed in one vertical line; but there was no direct connexion between the crank and the piston-rod to the paddle-axle, the communication of motion to it being effected through the medium of toothed wheels. In the common or lever engine the piston-rod acts on a cross-head, the cross-head on side-rods, the side-rods on side-levers, the lever on a cross-tail, the cross-tail on the connecting-rod, the connecting rod on the crank-pin, by which through the axle the paddle-wheels revolve. In the engine of direct communication, the side-levers, and some other parts of the train of communication, are removed by a device which enables the piston-rod to be almost immediately attached by a connecting-rod to the cranks of the paddle-shaft. This plan was first adopted by Mr Gutzmer of Leith, who built a vessel called the Athole, and another called the Tourist, on this principle; but his method, though very simple, was not applicable in ordinary cases; and Mr Napier made se- Various modifications of the vertical engine, which, according to our judgment, include all the best that have yet been introduced. It does not seem to have been practically established that the engine of direct connexion is preferable to the lever engine; but the plans of Mr Napier appear to have been the best ever adopted.

It is now a considerable time since Mr David Napier relinquished all connexion with such operations on the Clyde; since his retirement, much has been done for the advancement of steam navigation in Britain, and to this work the ship-builders and engineers of the Clyde have contributed their full share. We have already stated that a regular communication by steam was early established between Liverpool and the river Clyde. This establishment has done much for the advancement of steam navigation. It has afforded scope for two extensive companies, who, employing the most eminent steam-engine and ship-builders for the construction of their ships, have produced a very superior class of vessels.

The introduction of wrought-iron hulls for steam vessels, has been the means of introducing a great improvement in the art. This method of construction enables builders to effect a combination of strength and lightness of draught, peculiarly advantageous in some branches of trade and in certain localities. One of the first iron steam-vessels was the Alburkha, of 55 tons. It was built to accompany the Quorra in the expedition to the Niger in 1832, and gave very great satisfaction. The builders of the Alburkha, Messrs Laird of Liverpool, immediately afterwards commenced another vessel, the Garry-Owen, destined to run between Limerick and Kilrush. The length of this vessel was 125 feet on deck, its beam 21 feet 6 inches, and its engines were fifty horse power each. The Garry-Owen was driven on shore, with many other vessels, in the great hurricane which happened about that time, and alone escaped uninjured. This, and other evidence of the power of iron vessels to withstand the casualties of the sea, so raised them in the estimation of builders, that their number was rapidly increased, and their size greatly extended.

For a long period there had been much speculation about the practicability of navigating the Atlantic by steam. So early as 1791, and while the steam-boat was yet in embryo, Fitch, the American, boldly predicted that sailing vessels would soon be superseded in transatlantic navigation. In 1819, an American steam-ship, the Savannah, of 300 tons' burden, arrived at Liverpool direct from the United States, having accomplished the passage in 26 days, partly steaming and partly sailing; and nearly ten years after, the Curacao, an English-built vessel of 350 tons and 100 horse power, made more than one successful run in the same manner, between Holland and the Dutch West India colonies. Men of science, however, endeavoured to demonstrate that the navigation of the Atlantic by steam-power alone, was the dream of a visionary, and the tide of public opinion seemed to set in the same belief; but a strong undercurrent was at work, and in 1838 the following advertisement appeared in the daily papers: "Steam to New York. The well-known steam-ship, Sirius, Lieutenant Roberts, R.N., Commander, is intended to leave London for New York on Wednesday 28th March, calling at Cork harbour, and to start from thence on Monday the 2nd of April, returning from New York the 1st of May."

Thus, a company of merchants was found sanguine enough to disregard the demonstration of the impossibility of an American voyage, and actually to advertise not only the day of sailing, but also the days of arrival and return. The Sirius was not expressly built for transatlantic navigation; she belonged to the St George Steam-Packet Company, and had run with a good reputation between London and Cork. Her tonnage was about 700 tons, and her engine about 320 horse power.

Although advertised to sail on March the 28th, circumstances delayed her departure till the morning of the 4th April, when she started at ten o'clock, with 94 passengers. Though first in the race, she was only three days in advance; for on the 7th of the same month, the Great Western, built and fitted expressly for the purpose, followed her. In the interval, between the sailing of these vessels and the reports of their arrivals, much doubt prevailed as to the possibility of their accomplishing their task in safety, and the uncertainty was increased by vessels having arrived from America at ports in Britain, without having encountered either of the steamships; people having, for a moment, forgotten that there were more roads than one across the Atlantic. They were at length, however, spoken with by the Westminster, the Sirius on the 21st, within six hours' sail of New York, and the Great Western on the 22d; and in due time, reports of their having reached New York arrived, the Sirius on the 22d, being 17 days clear on the passage, and the Great Western on the 23d, being 15 days. The Sirius again sailed on her homeward passage on May 1st, afternoon, and the Great Western on May 7th, and they arrived, the first on the 18th, and the latter on the 22d, being 16 and 14 days respectively. The average speed, and expenditure of fuel of the Great Western was as follows. The whole distance run from Bristol to New York was 3125 miles, averaging each day 208 miles, each hour 8-2 miles; the distance run in returning from New York 3192 miles, each day 213 miles, each hour 9 miles nearly. She departed with 860 tons of coals, and on her arrival at New York she had 205 tons remaining. She left New York with 570 tons of Newcastle coals, and had on board when she arrived at Bristol 178 tons. Her average daily consumption was 27 tons; and, with the expansion valves up, 32 tons. In page 707 there is given a table exhibiting a comparative view of the size and power of six of the largest of the transatlantic vessels.

The practicability of transatlantic navigation being thus fully demonstrated, preparations for its continuance on a gigantic scale commenced, and the British Queen, the President, and other vessels of enormous size, were launched in rapid succession. In addition to these, the offspring of a state of peace, steam war vessels, of great size, are daily constructing, and call for the highest ingenuity of the ship-builders and engineers, in adapting them for taking the advantage of their sails as well as of their steam-paddles.

While the art was thus rapidly advancing, many ingenious men were making attempts to improve the form of the paddle-wheels, or to substitute for them some other impelling apparatus. Of the improvements in the paddle-wheels themselves, we shall have occasion to speak in the sequel. We shall, therefore, in this place, give some account of the most important of the substitutes, the Archimedes screw propeller. The idea of impelling a vessel by means of a screw of a large diameter, lying in the direction of the boat's motion, was originated some considerable time ago; but its first successful application was to a vessel named the Archimedes, constructed under the direction of the patentee of the screw, Mr Smith. From an interesting report of experiments made with this vessel by Captain Chappell, R.N., we condense the following statement:

—The burden of the Archimedes is 237 tons, its mean draught of water 9 feet 4 inches. The diameter of the engine cylinder 37 inches, and the length of stroke 3 feet. The screw propeller consists of two half-threads of an 8 feet pitch screw, 5 feet 9 inches in diameter; each is therefore 4 feet in length, and they are set diametrically... Steam Navigation.

opposite to each other on the propeller shaft, at an angle of 45 degrees to the shaft. The propeller is placed longitudinally in a hole cut in the dead wood, immediately before the rudder, the keel being continued under the screw. The average performance of the engines is 26 strokes per minute, and the revolutions of the screw in the same time 1383. If there was no slip or recession, the vessel ought to advance 8 feet for every revolution of the screw, or 12.60 miles per hour. The utmost speed ever obtained by her, under the power of steam alone, was 9.25 nautical miles per hour, showing a loss by recession of rather less than 1/3th, under the most favourable circumstances. It is necessary to state that the Archimedes is not a fair exemplar of the screw-propelling principle, its steam-power being insufficient to drive a screw adapted to the size of the vessel.

The advantages of this species of propeller appear from Captain Chappell's statement to be these:—1. It occupies a position in the vessel in which it is not liable to injury, and in which it materially augments the power of the helm, enabling the vessel to be turned round and round in circles gradually smaller, until at length it seems to revolve on a pivot. 2. It retains its efficiency of action, even in heavy seas, the rolling, pitching, or lurching of the vessel not materially affecting it. 3. It offers little obstruction to the speed of the vessel, when the sails alone are employed. When to these are added the saving of expense, which is said to be great, and the removing the top-weight and unsightly paddle-boxes, we are of opinion that there is enough in its favour to recommend its further trial.

We have now traced the art of steam navigation from its first suggestion to its present state of high perfection. We have overlooked, it is true, much that is interesting in the minute progression of the art; but we have endeavoured to mark its greater advances. We have seen its advancement in the short period of a quarter of a century, from the canal boat experiment of Symington, and the three horse steam-boat of Bell, to the construction of the monster ships, the British Queen and the President, of 500 and 600 horse power. When, in 1820, steamships were first used for conveying merchandise, as well as passengers, the tonnage of the whole of the steam-traders amounted to only 505 tons. In 1821, it amounted to 36,194; in 1822, it had reached to 101,744 tons; and thus advancing, it had arrived, in 1836, at the prodigious amount of 5,429,226 tons. The number of vessels of the mercantile marine, with their power and tonnage, is exhibited in the following table.

An Account of the Approximate Number, Tonnage, and Power of Vessels belonging to the Mercantile Steam Marine of the United Kingdom and its dependencies, at the close of the year 1839.

| SIZE OF VESSELS | Total Number of Vessels according to the Custom-House Returns in 1838 | Total Registered Tonnage | Tonnage of Engine-Room, &c., not Registered at the Custom-House | Total Computed Tonnage | Total Computed Amount of Horse power | Average Computed Power per Vessel | Average Computed Tonnage per Vessel | |----------------|---------------------------------------------------------------|--------------------------|---------------------------------------------------------------|------------------------|-------------------------------------|-----------------------------------|-----------------------------------| | Under 50 Tons | 256 | 6,106 | 10,816 | 16,922 | 6,400 | 25 | 66 | | From 50 to 100 Tons | 145 | 10,267 | 7,458 | 17,725 | 6,866 | 47 | 122 | | 100 ,, 150 ,, | 84 | 10,084 | 7,761 | 17,845 | 7,483 | 90 | 211 | | 150 ,, 200 ,, | 63 | 10,982 | 7,147 | 18,129 | 7,560 | 120 | 287 | | 200 ,, 300 ,, | 76 | 16,654 | 10,839 | 27,493 | 11,188 | 147 | 361 | | 300 ,, 400 ,, | 41 | 14,247 | 7,580 | 21,827 | 10,914 | 266 | 332 | | 400 ,, 600 ,, | 10 | 4,488 | 3,506 | 7,994 | 3,000 | 300 | 769 | | 679 ,, | 1 | 679 | 661 | 1,340 | 450 | 450 | 1,340 | | 1,053 ,, | 1 | 1,053 | 810 | 1,855 | 500 | 500 | 1,855 | | Number of vessels Registered in 1838 | 677 | 74,510 | 56,378 | 131,080 | 54,361 | ... | ... | | Not Registered | 83 | 4,154 | 5,484 | 9,638 | 2,129 | 50 | 116 | | Total Number in Great Britain and Ireland 1838 | 760 | 78,664 | 62,062 | 140,718 | 56,490 | ... | ... | | Isles of Guernsey, Jersey, and Man, 1837 | 6 | 832 | 618 | 1,450 | 600 | 100 | 241 | | British Plantations, 1837 | 44 | 8,411 | 7,253 | 15,664 | 6,160 | 140 | 356 | | Total | 810 | 87,937 | 69,933 | 157,840 | 60,840 | ... | ... |

THE THEORY AND PRACTICE OF MODERN STEAM NAVIGATION.

There is perhaps no popular error more injurious to the welfare of a mechanical nation, like our own, than the notion that theory is opposed to practice; and there is no subject in which this error has ever been more disastrous than in steam navigation, and naval architecture in general. It is by the combination of theory and practice that most is to be accomplished; and it may be hazarded as a general assertion, resting on all past experience, that the best promoters of the public welfare are—that theoretical man who has made himself best acquainted with the practice of his art, and that practical man who has acquired the greatest knowledge of its scientific principles. There is no art which does not attest this truth, and none attests it more than steam navigation. It is admitted, that out of every three steam vessels that are built, two fall very far short of fulfilling the intention with which they were We believe there is no error which it may be possible to commit in steam navigation, that has not already been perpetrated again and again.

To construct a perfect steam-vessel, it is necessary first of all to make a perfect ship; secondly, to construct a perfect steam-engine and boilers of a very complex description; thirdly, to apply a propelling apparatus of the most appropriate description; and finally, to combine all of these in a perfect and well-proportioned whole. Now, to construct a perfect ship, is itself a problem of the highest order, requiring a combination of the most profound resources of analysis, with the highest practical sagacity; a problem on which the reasoning of the mathematician, and the tact of the artist, have long been engaged, with few examples of complete success. To construct a sufficient, effective, powerful, durable, and safe engine and boilers for marine purposes, is a problem more easy, yet one in which there has been encountered continual failure. Then, the means of propelling the vessel over the element on which it floats, give rise to questions in the resistance of fluids which all the resources of hydrodynamic science, in the hands of the ablest mechanical philosophers of the last century, have failed to resolve. Then, last of all, the combination of all of these together, in the best possible way to bring about the precise effect desired, is a problem still more arduous; and all the skill of the analyst, the geometer, the mechanical philosopher, of the naval architect, the engineer, the mechanic, and the sailor, if combined in a single individual, or concentrated on a single object, are not more than sufficient to the arduous task of directing the wealth, enterprise, and resources of this country, in the attempt to render available to her own prosperity, and the interests of the human race, this most admirable of all her creations.

In the following enquiry, we shall soon see that neither practical experience without systematized knowledge, nor superficial theory ignorant of practical wants and practical means, will suffice to ensure success. Both physical science and practical sagacity will, in the art of steam navigation, find enough to exhaust their united resources.

We regret that we cannot record in the present work, that at this day the science of steam navigation is constructed and can be presented to our readers. Even the elementary principles of hydrodynamics are yet to be learned, before we can apply them to the ends of steam navigation. What seems the law of a fluid to-day, tomorrow shows to be a plausible fiction, or doubtful verisimilitude. How then can it be expected that a science should be determined, when its very foundations are yet to be laid? We shall, however, endeavour to generalize what we with certainty know, convinced that a clear statement of our ignorance is often the stepping-stone to truth. The steam-ship consists of three integrant parts: the marine-engine, with its boilers, by which the moving power is furnished; the propelling apparatus, by which it is rendered locomotive; and the ship itself, which contains both. We shall consider each apart, and then their combination.

The Marine Steam-Engine.—The marine steam-engine is of a structure more complex than the common fixed steam-engine, insomuch as its function is locomotive, and it differs from a land-engine in those peculiarities which adapt it to the unstable nature of its support. He who looks at the ponderous masses of matter that form and sustain the shock of a powerful engine on land, the beams of iron, the blocks of stone, the deep buttresses, and the powerful walls which form its bed, on which it is adjusted at once with the greatest accuracy and power, and which it nevertheless causes to quiver and tremble Steam Navigation by its giant strokes, will readily understand the incredulity with which the first projectors of steam navigation were regarded.

The earliest application of the steam-engine was to the pumping of water. We find that when it was first used to the effect of making machinery revolve, the great lever of the pumping-engine was retained. So was it in the application of the steam-engine to navigation; and the marine steam-engine, most generally used at the present day, both here and in America, is called the beam-engine, or lever-engine.

The first of the following diagrams represents the beam-engine, or lever-engine, as used on land to turn round machinery; the second represents the lever-engine, as used in America to give revolution to the paddle-wheels of a steam-boat; and the third represents the lever-engine of British steam-vessels.

In all of these figures, S represents the place of the steam-cylinder, in which, by the alternate action of the steam on opposite sides of the piston P, that and the piston-rod P B are forced alternately to the top and bottom of the cylinder; and so the end of the lever or great beam B B is carried up and down around the centre M, carrying with it the connecting rod K B', by whose reciprocation the crank-pin K, of the crank radius K X, is carried round on the great revolving shaft X; which, in the case of the marine engine, is the axis of the paddle-wheel, and in the case of the stationary engine, is the axis only of the fly-wheel. V is the place of the valves by which steam is admitted from the boiler into the cylinder, and, after having done its duty, is educted into the condenser C, where, by a jet of cold water constantly playing, it is immediately condensed into water of the seventeen-hundredth part of its bulk, and so leaves the cylinder empty, i.e., nearly a perfect vacuum; and as this condensing receptacle would soon, by the jet of cold water flowing into it, and the accumulation of condensed steam, be filled with water and its evolved gases, the air and water are pumped out at each stroke of the engine by the air-pump A, worked from the lever or working-beam B B, and so the vacuum is kept perfect and the condenser effective. The feed-pump F replenishes the boiler G with some of the water extracted from the condenser, at a temperature of about 90°, and so supplies the deficiency caused by the con- Steam Navigation.

The differences between the arrangements of the marine steam-engine used in Great Britain, and the land steam-engine, are chiefly these: the lever or great beam, which, in the land-engine, is above the top of the engine, and which in large engines is generally composed of a pair of thin deep beams of cast-iron, united side by side into one; this single beam is brought down in the marine engine to the bottom of the engine, or rather one-half of the great beam is placed on either side of the cylinder, the two being connected together from the opposite sides of the engine, so as to act simultaneously as a single lever. This form of engine, sometimes applied to other purposes as well as to navigation, is called, from this disposition of the working beam, the side lever engine.

Another peculiarity in the marine-engine, sometimes however adopted in land-engines, is the place and arrangement of the condenser C, which, instead of being placed in a cistern of water, is set immediately on the centre of the engine, the condensation being wholly effected by the play of the jet of water in the interior of the condenser, without surrounding its external surface with cold water, as in the stationary engine. When thus placed, the condenser has also the advantage of giving support to the main centre of the engine, around which the levers move in giving revolution to the paddle-wheels.

Before proceeding further with this article, the reader is requested to make himself familiar with the parts and arrangements of the engine already described, by referring to the plates of the marine-engines given at the end, and to the descriptions of them.

It will be observed that the air-pump A is generally placed on the side of the engine furthest from the cylinder. This arrangement is convenient in point of room, and keeps the moving parts of the engine itself more perfectly in equilibrium.

Beside the air-pump is generally placed the feed-pump, designed to force water out of the air-pump or discharge-pipe into the boiler. This is the general disposition of parts, which the reader will easily be able to recognise in the plates given with this article.

Although the lever-engine is the form most commonly employed for marine purposes, it is by no means the only form. Very many attempts have been made to obtain engines more compact and of less weight and bulk than the lever-engine. These are distinguished from the lever-engines by the names vertical engines, steeple-engines, and engines of direct connexion. It is still doubtful whether any of them, except in very peculiar circumstances, are practically to be preferred to the lever-engine; on the contrary, objections of a serious nature are alleged against them.

We have already seen that the first steam-boat, the Comet of Mr Bell, had a vertical engine. It was remarked of this vessel that the strain of the engine on the vessel was very small; but this has been attributed to the low proportion of power to the tonnage of the vessel.

The first steam-vessel whose engines we had the pleasure of seeing, had a pair of vertical engines, made by Gutzmer of Leith; the paddle-shaft B being directly over the axis of the cylinders A, as in figs. 4. and 5.

Modifications of this plan of direct or immediate connexion have been recently tried on a larger scale; but the method has the disadvantages of admitting only a short stroke and a short connecting rod, and requires that the height of the axis above the bottom of the cylinder should be at least three times the length of the stroke. Thus, one of the extremes, too short a connecting rod, too short a stroke, or a paddle-axis too high above the floor of the vessel, is incurred.

To obtain the same object without incurring those evils, many descriptions of engine have been contrived. The following admits of placing the paddle-axis at little more than double the height of the stroke of the engine, and gives a connecting rod of $1\frac{1}{2}$ or 2 times the stroke. The piston-rod P is inserted into a cross-head d d, to the extremities of which two vertical rods d e, d e, are attached. With the lower extremities of these rods the side-rods g f, g f, are connected; the upper ends of these side-rods are attached to the cross-head g g, to the centre of which the crank-rod is attached.

This species of engine has the great disadvantages of a multiplicity of shafts, bearings, and cranks. It was afterwards simplified by Mr David Napier in the manner represented in the following figures; viz. by uniting into one forked cross-head each cross-head with its side-rods.

Even thus, however, limits are placed on the length of stroke and height of shaft, so as to give rise to inconvenience in many circumstances. To remedy these evils, Mr Napier appears to have invented the following class of engines, to which the cant term of steeple-engines appears to be sufficiently appropriate. In the steeple-engine the piston-rod is made forked or divaricated, so as, passing round the shaft, to rise above it to a considerable height, from which again descends the connecting rod to the crank. The following example is that The top of the piston-rod carries a quadrupartite crosshead \( h \), on each end of which stands a pillar \( h \); these four pillars again unite in another quadruple crosshead, sustained upright by a vertical guide; and it is from this summit that a connecting rod descends to the crank \( k \). We believe that this principle of continuing the piston-rod round the axis by a forked frame was first devised, at the end of the last century, by Trevithic, the famous high-pressure engineer, and by him applied to steam-carriges. It is drawn in his patent specifications.

After passing through a great variety of phases, the steeple-engine appears to have settled down into the two following shapes. In figs. 14 and 15, the piston-rod is seen united to a triangular frame, from the apex of which the connecting rod descends to the crank. In fig. 16, this frame is shown to be square, and fig. 13 is the side view of both varieties.

Another method of accomplishing the direct connection without encumbering the deck, has twice been patented; in the last instance by Mr Humphreys. It may be called the trunk-engine. The axis is placed at the height of half the stroke, or more, above the cylinder, and a connecting rod unites immediately the crank-pin with the centre of the piston. In this way the connecting rod, passing through the top of the cylinder, would allow the steam to escape but for a large trunk or casing with which it is surrounded, and which, passing through a chasm of large area conceived to be steam-tight, rises and falls with the piston to which it is attached. In fig. 17, \( A \) is the cylinder; to its piston is attached a trunk \( B \), which works through a stuffing-box in the cylinder cover; to the piston the connecting rod \( c \) is attached. Fig. 18 represents the top of the cylinder \( A \), with its stuffing-box and the trunk \( B \).

For a like purpose, oscillating cylinders have been used with some measure of success. Rotatory engines have been unsuccessfully tried. The reader may now examine the vertical engines in the plates.

In short, it does not appear that any vessel, either on a large or small scale, constructed with an engine different from the ordinary side lever engine, has been found to be practically superior to it; and therefore we shall for the future speak of the lever-engine of the ordinary construction, when we treat of the marine steam-engine, unless when another species is expressly mentioned. The lever-engine possesses three advantages of an important nature:—first, its parts are nearly in equilibrio; secondly, its basis embraces a large part of the vessel's bottom for strength; thirdly, the lever presents great facility for working its appendages.

The Cylinder of the Marine Steam-Engine.—The cylinder of the steam-engine being that portion of its apparatus, by means of which the elastic force of the steam Engine is directly applied to the mechanical arrangements by which the force of the machine is developed, is therefore the principal member of the engine, on the size of which its powers and the dimensions of the other parts depend.

It is according to the dimensions of the cylinder that an engine receives its denomination, and is bought or sold. An engine is called a 10, 20, 50, or 100 horse-power engine, according to the number of inches in the diameter of the cylinder. It is not to be expected, however, that every steam-engine will develope the power of a given number of horses, simply because it has a cylinder of a given number of inches. This depends equally on the proper proportion, construction, and condition of all the other parts, without which the engine will be incapable of doing its proper duty. The engines of some makers will develope double the power of those made by inferior engineers, even although in name and dimensions identical. Hence, the dimension of cylinder is taken according to a rule somewhat arbitrary, of the value both dynamical and pecuniary of the engine under the term nominal power; and the actual efficiency of the engine under given circumstances, is called the real or effective power. Hence an ambiguity is incurred in speaking of the relative powers of engines, when it is not determined whether the real or nominal power is referred to. An engine of 100 horse power, which ought to be capable of giving out an effective power of 100 horses, may, from bad workmanship, bad arrangements, or modified circumstances, only give out the real power of 50 horses; and an engine of the same dimension of Steam Navigation.

Steam Na-cylinder, and of the same nominal power, but of better construction, may give out, and frequently does give out, real and effective power equal to that of 150 horses. Real or effective power, and nominal or mercantile power, are seldom identical, and should always be distinguished from each other.

Even the nominal or mercantile standard of power is not so perfectly invariable as may be desired. It varies a few inches according to the practice or policy of the engineer, who is frequently called upon to give an inch or two more in his mercantile dimensions, than the strict letter of his agreement might demand. Another cause of variation is this, that some engineers will prefer to sell a larger actual dimension under the name of a less number of horse power, that their engines of a given nominal power may apparently do more work than those of other people. It is a third cause of variation, that some engine-makers give more than the actual dimension belonging to the power, in order that, under even the most unfavourable circumstances, the possessors of the engine may derive from it more than the full measure of the actual effective power which they require.

The following table has been constructed from a comparison of the practice of the most eminent marine steam-engine makers, with the principles of their construction. But under the dimensions given, the engines of best construction will give out from one-fourth to one-third more than their nominal power. We know, for example, that a cylinder of 74 inches diameter has been constructed under the designation of 200 horses, whereas its proper nominal power is above 225 horses, and its actual effective power, as given out in the ship, was more than 300 horses. The contraction H.P. is generally used instead of the words horse power.

Table of the Dimensions of the Cylinder of a Marine Steam-Engine of given Horse power.

| Nominal Power | Diameter (within) | Length of Stroke | |---------------|------------------|-----------------| | 10 H.P. | 20 Inches | 2 Feet 0 In. | | 15 " | 24 " | 2 " 2 " | | 20 " | 27 " | 2 " 6 " | | 25 " | 30 " | 2 " 10 " | | 30 " | 32 " | 3 " 2 " | | 35 " | 34 " | 3 " 3 " | | 40 " | 36 " | 3 " 6 " | | 45 " | 38 " | 3 " 9 " | | 50 " | 40 " | 4 " 0 " | | 60 " | 43 " | 4 " 3 " | | 70 " | 46 " | 4 " 6 " | | 80 " | 49 " | 4 " 9 " | | 90 " | 52 " | 5 " 0 " | | 100 " | 55 " | 5 " 6 " | | 110 " | 57 " | 5 " 6 " | | 115 " | 57 " | 5 " 3 " | | 125 " | 59 " | 6 " 0 " | | 130 " | 60 " | 6 " 0 " | | 150 " | 62 " | 6 " 3 " | | 165 " | 65 " | 6 " 6 " | | 175 " | 66 " | 6 " 6 " | | 200 " | 70 " | 7 " 0 " | | 225 " | 73 " | 7 " 3 " | | 250 " | 76 " | 7 " 6 " | | 275 " | 79 " | 7 " 9 " | | 300 " | 82 " | 8 " 0 " | | 350 " | 87 " | 8 " 6 " | | 400 " | 92 " | 9 " 2 " | | 500 " | 100 " | 10 " 0 " |

This table shows that the power of the steam-engine increases more rapidly than the area of the cylinder or the square of the diameter. By the rule of the square of the diameter, the power of an engine of 74 inches would be about 200 instead of about 225; and 100 inches diameter would give only 333 horse power; but the same rule would give too small a diameter for the lower powers. We believe that engines of the dimensions of this table will all work to more than their nominal power.

The best proportion between the diameter of the cylinder and the length of the stroke, has been the subject of much dispute, and of opposite practice. In America, a diameter of 40 inches is sometimes combined with a stroke of 10 or 11 feet, being more than double the length given in this country. On the Clyde, we have seen the opposite extreme, a diameter of 60 inches with a stroke of only 4 feet. For sea-going ships, the proportions we have given are the most convenient. In deviating from this proportion, a longer stroke will be preferable to a shorter; and with the necessary alterations required for high velocities of piston, a longer stroke working the steam expansively is likely to be attended with many advantages.

By means of a long stroke or great velocity of piston, considerable advantages are gained. The pressure upon the journals and working parts of the engine, and the consequent strain, is lessened in proportion to a given power. All the parts of the engine might be lighter than with a shorter stroke and a greater diameter of cylinder. A short stroke has however this advantage, that with a given length of lever and connecting rod, the angles of oblique pressure are smaller, and the intervals of time between maximum and minimum pressure are shorter. There are other peculiarities of smaller importance. On the whole, a longer stroke than that of the present British engine, as given in the table, is to be reckoned considerably preferable to a shorter one.

The velocity of the piston in the cylinder of a steam-engine is generally reckoned in this country at 220 feet a minute, and all the arrangements of the engine and its work are made on that principle. We can find no better reason for this than that a horse going at that speed, viz. two miles an hour, can draw 150 lbs. eight hours a-day, all the year round. Tredgold finds it to be a law of nature. It is strange how much this arbitrary dogma, transmitted without question, has retarded the improvement of steam navigation. It is a rule as universal in its acceptation as it is groundless and injurious. With large condensers, and large ports and valves, double the speed may be employed with great advantage.

The Condenser and Air-Pump.—The condenser is the most wonderful part of the marine-engine, as indeed of the ordinary steam-engine. It is here that the whole process carried on in the boiler in so great bulk, and at so much expense, is instantly reversed, and all its laborious effects at once, as it were, annihilated. It is the instantaneousity of condensation that is its virtue: without this the whole of its virtue in the steam-engine is lost. Suppose a condenser capable of condensing the steam as fast as it is generated by the boiler, and given off in the cylinder, and no faster, what would be the consequence? The power of the engine would cease, the elastic force of the steam above the atmosphere would alone act, the steam being only condensed as the piston carried it out of the cylinder; the engine would become nothing else in power but a high-pressure engine, whose steam is merely condensed before going out into the atmosphere. It is by forming a perfect vacuum in the Let \( t \) = the caloric of water of 1°. \( c \) = the constituent caloric of water in the state of steam. \( e \) = the total force of steam in the boiler in inches of mercury; and \( x \) = the elastic force of steam at the temperature of best condensation which we seek to discover.

Then from the law which connects the elastic force of steam with temperature, as already determined in the article Steam, it follows, that in the case of maximum effect, or the temperature of best condensation,

\[ \frac{t}{c} = \frac{x}{e} \]

that is \( x = \frac{et}{c} \)

now \( c = 1000 \), and if the steam in the boiler be at 5 lbs. above the atmosphere, or if \( e = 40 \) inches of mercury, and \( t = 1 \),

\[ x = \frac{40}{1000} = 0.04 \]

Again, if the steam be at \( 7\frac{1}{2} \) lbs. = 45 inches,

\[ x = \frac{45}{1000} = 0.045 \]

Again, if the steam be at 10 lbs. = 50 inches,

\[ x = \frac{50}{1000} = 0.05 \]

Hence, we find that the best elasticity or temperature in the condenser depends on the elastic force of the steam in the boiler.

With steam of 5 lbs. in the boiler, the elasticity of maximum effect in the condenser is at 93° of Fahrenheit, and the best vacuum in the barometer is 28. With steam of \( 7\frac{1}{2} \) lbs. in the boiler, the elasticity of maximum effect in the condenser is 95° of Fahrenheit, and the best vacuum in the barometer is 27.8. With steam of 10 lbs. in the boiler, the elasticity of maximum effect in the condenser is 97°, and the best vacuum in the barometer is 27.5. In like manner it would be found that with steam of 50 lbs. in the boiler, worked expansively, as in Cornwall, the best vacuum in the condenser would be about 26° on the barometer.

It is hoped, therefore, that engineers will not in future distress themselves, at finding the vacuum of their condenser much less perfect than the vacuum of others who have obtained 30, and 30\(\frac{1}{2}\) inches, at so great a loss of fuel and power. To obtain a vacuum of 29\(\frac{1}{2}\) with the weather-glass at 29.75, and steam at \( 7\frac{1}{2} \) lbs., would be to sacrifice four horse power out of every hundred. In a day when the barometer is as low as 28\(\frac{1}{2}\) inches, the vacuum in the condenser should indicate 26.8.

In speaking of the vacuum in the condenser, it would save much ambiguity to indicate the elasticity merely of the gas in the condenser. Thus, if the barometer stands without at 29\(\frac{1}{2}\), and the barometer of the condenser at 28, it might be stated that the steam in the condenser stands at 1\(\frac{1}{2}\), being the point of maximum effect; and the indication would at all times convey more precise information.

An air-pump is an appendage rendered necessary by Air-pump the condenser, and especially by condensation by jet of marine d'eau. Ordinary water contains about 5 per cent. of engines, air and other gases, which become disengaged in the condenser, and must be withdrawn, to maintain the vacuum. Hence the air-pump, which is also used to withdraw the water which accumulates in the condenser. A valve between it and the condenser is called the foot valve; and a valve at the exit from the top of the air-pump is called the discharge valve. They are thus arranged: S the cylinder, C the condenser, A the air-pump, F the foot valve, and D the discharge valve. The dimensions of the air-pump seem to vary much, from \( \frac{1}{2} \) to \( \frac{1}{3} \) of the volume of the steam-cylinder. I do not know any disadvantage of importance in having a large air-pump; as, if properly constructed, the force which is required to work it will be nearly in the proportion of the elasticity of the gas which it has to remove from the condenser. To give the air-pump half the stroke of the cylinder and \( \frac{1}{2} \) of the area of the cylinder, or \( \frac{1}{2} \) of the stroke of the cylinder and \( \frac{1}{2} \) the area of the cylinder, are common proportions.

The Valves and Valve Passages.—The notion that because a horse can do most work at the rate of 2½ miles an hour, or 220 feet a minute, therefore a steam-engine should also move at that rate, is a prescriptive error almost ridiculous; but from which it will nevertheless be difficult for us to escape, especially as the proportions generally in use are derived from this absurd dogma. There is no doubt that the passages and valves should simply be as large as possible, and those valves should be used which can be most enlarged with least inconvenience. Such valves we possess in the class of equilibrium valves. These valves may have an area as large as the tenth-part of the cylinder without disadvantage, and the velocity of the piston may thus be increased, and consequently the power of the engine, with great advantage, especially in steam navigation. We have the best possible means of knowing, that with proper valves and passages, the speed of the piston may very advantageously be increased to 250, 300, 400, and 500 feet a minute. The pistons of the swiftest vessels in the world move at that rate.

The kind of valve most commonly in use in steam-vessels is the long D-slide, as it is called; and next to that is the short D-slide. There are scarcely any other kinds in use in Britain. A valve called the four-port slide valve has been used to a limited extent, as have also conical valves, and equilibrium valves, or double heat valves in this country, the latter very extensively in America. The following are diagrams of the long and short D-slides.

As the shaft A moves round, it is plain that the projection of the eccentric, first on one side of the shaft and then on the other side, will draw the eccentric rod in opposite directions; and the distance of the centre of the eccentric from the centre of the shaft, will be placed now on one side and now on another side of the axis. The motion thus produced is called the throw of the eccentric; and half the throw is equal to the eccentricity. An important point in setting the valves is what is called the lead on the centres. What is the best instant of time at which to allow the steam to enter or escape from the cylinder? At first sight we should say, precisely at the instant of reversing the direction of the motion. This is not the case. Great advantage is gained by letting the steam out of the condenser before the end of the stroke. A little of the force of the steam in the cylinder may thus be sacrificed; but it is a very little, say \( \frac{1}{50} \)th of the stroke, and is much more than compensated by this, that the steam escaping thus early into the condenser, time is allowed for effectual condensation, and there is an excellent vacuum in the cylinder by the time when the back-stroke begins. In like manner, the steam-port may be slightly opened before the engine comes to the centre; and as there are vacuities at the top of the cylinders to be filled, and as time is wanting for the passage of the steam, this is allowed. By the same means also the steam is cut off a little before coming to the end of the stroke, which allows the engine to work expansively; and the vacuum port may in like manner be shut, as the vapour will have been perfectly condensed in the cylinder long before the end of the stroke. Much of the efficiency of an engine depends on the adjustment of the slide.

The eccentric of the marine engine is generally a loose eccentric, capable of turning the valves either so as to give the engine motion forwards or backwards. By placing the eccentric loose upon the axis, only with a projection on one side, which is carried round by a corresponding projection on the axis, it is left free, except when this check comes in contact with the projection at either end of the stroke. To effect this, it is necessary to open the valves by hand through at least one half-stroke.

The Hand-Gear.—The hand-gear is generally a lever or series of levers, which enables the engineer to shut and open the valves by hand before placing them in connexion with the eccentric. By this means he places the machine either in the condition to keep moving forwards or backwards. For examples see the Plates.

The Expansive Valves.—It is of advantage to cut off a part of the steam which would be required to fill the cylinder, so as to allow that quantity which has partly filled it to expand with its elastic force, and fill the rest of the cylinder without further supply from the boiler. The advantage of doing this, especially in long voyages, has now become pretty generally known. A stop-valve \( V \), fig. 25, is placed on the steam-pipe \( S S' \), before it joins the casing of the common valves, which are applied as usual. The principal axis \( A \) of the engine carries a cam, with two projections proportioned in breadth to the extent of the stroke which is cut off. On this cam rolls a small pulley \( b \), pressed close by a weight \( w \); and by a simple connecting rod the cam opens and shuts the valve with great velocity twice in each revolution. On this cam there may be various grades at which the steam may be cut off in the stroke of the engine. This apparatus is used in all vessels calculated for long voyages.

The Proportion of Power to Tonnage.—Large power or small power has always been one of the vexatae questions of steam navigation. The early steam-boat engines had but a small power proportioned to the tonnage of the vessels in which they were placed. The Proper Comet had 25 tons burden and only three horse power; being about one horse power to eight tons, or a proportion of power to tonnage amounting to one-eighth.

On this subject modern practice and modern opinion seem to offer no guide. A low proportion of power and a high proportion of power have both their advocates. The East India Company have advocated and used low proportions of power to tonnage, and in this they appear to have followed the general maxims of southern engineers. The Government also appears to have adopted the same course; but without going to the same extreme. The Clyde engineers adopt the opposite maxim, and place as much power in their vessels as can be conveniently applied. There appears at the present moment to be a strong feeling in favour of a high proportion of power to tonnage. It has been found by some of the best mercantile companies, that a high proportion is not only better for expedition, but also more economical of fuel and of capital than a smaller proportion; and instances are frequent of an increase in the power of a steam-vessel, producing a diminution in the consumption of fuel.

As this question is becoming every day of greater importance, it is proper to examine it carefully. In the first place, it is well known that the proportion of power must be very much increased to gain a given increase of speed. Thus, if 120 horse power propel a vessel through water five miles an hour, it will require forty horse-power to propel the same vessel ten miles an hour, or it will require a quadruple power to obtain a double speed; and, in like manner, it will require a ninefold power to triple the speed. In fact, the increased speed requires an increased power in a duplicate ratio of the increased speed; or if the speeds be as the numbers 1, 2, 3, 4, 5, 9, 10, &c., the power required to attain those speeds must be 1, 4, 9, 16, 25, 81, 100 horses; or according to the well known law of the resistance of fluids, the resistance which the water opposes to increased speed is nearly in the duplicate proportion of the speed. Thus, to increase the speed in a given proportion, the fire of the engine and the consumption of fuel, which is nearly as the power of the engine, must be increased in a very high proportion. Hence the seeming great economy of a low power of engine and a small consumption of fuel.

Thus a large power of engine occupies much of the useful space of the vessel, which might have been filled with cargo. It consumes much coal, and the speed is by no means proportioned to the expense of fuel and machinery. But this is a very limited view of the subject. If time as an element, and a very important one in the value of mercantile conveyance, be calculated, then it will in many cases be found, that high speed at any expense of fuel will compensate for that expense. This is the case to a great extent in Britain, and especially in America, where a quarter of a mile an hour between the speed of two vessels ruins the fortune of one owner, and makes the fortune of another. But it is not on the value of speed at the present day, that we proceed in this enquiry; that can at once be appreciated by the local peculiarities of a given case. We are to enquire what may be the best proportion of power to tonnage in sea-going vessels, apart from the mere price of speed in the market.

We have seen that the lowest speed in a steam-vessel is the most economical, and that it requires great and expensive additions of power to gain high velocities. But in arriving at this conclusion, we have taken only the case of smooth and still water. Here it is obvious that the slowest rate and smallest power will be most economical; but it should be remembered that the great purposes of steam are generally of a different nature from the mere generation of motion through a quiescent fluid. The force of adverse winds and waves is to be opposed, stream-tides and currents are to be stemmed; and it is the success of steam in conquering those obstacles, and obtaining regularity and speed in spite of them, which constitutes its superiority over wind or animal power in navigation.

Now, if we take a simple case of one of these, we shall soon find that a higher proportion of power to tonnage may be essential, not only to speed, but even to economy. Suppose a steam-boat with a small proportion of power, capable of propelling the vessel at the velocity of three miles an hour through still water, to be applied to stem a current of three miles an hour, is it not plain that the vessel would make no head way, and thus a low proportion of power would burn an immense quantity of coal in doing nothing but standing still?

Let us again suppose that the same vessel, capable of steaming three miles an hour, meets with a moderately strong breeze opposed to her, such as prevents her from making any progress at all against it; then it is plain that by the continuation of this breeze, the vessel burning a continual supply of fuel would consume an indefinite quantity of coal in standing still. This extreme case of too little power, shows that there is at least one proportion of power, which is too small for economy of fuel; viz., that proportion which, being very economical of fuel in fine weather, is brought up altogether by adverse winds. In this case, the consumption of fuel is rendered indefinite, and the useful effect of fuel completely annihilated by too small a proportion of power.

As, then, we have plainly established the existence of a limit to diminution of power, in the vicinity of which it must be followed by extravagant consumption of fuel, we may now proceed to investigate the question of best proportion, or the point where the attainment of high speed is accompanied by absolute saving of fuel as compared to lower velocity. For this purpose, we merely take it for granted that the speed through the water will be nearly as the square root of the power, according to the general law of the resistance of fluids; that the resistance offered by bad weather or adverse winds has been ascertained and is determined on a particular station; that is, that it is known that on a given station a given vessel with a given power makes a voyage in adverse circumstances in, suppose, double the time of her most prosperous voyage: say her most prosperous voyage is in fourteen days, and her adverse voyage in twenty-four days, being a retarding power of ten days out of twenty-four; we take this retardation of ten days as the measure of the retarding power of adverse weather in the given circumstances.

And further, let the following quantities be thus represented:

Let \( h \) be the power, \( v \) the velocity, \( f \) the fuel consumed, \( t \) the time in good weather, Let \( h' \) be the power, \( v' \) the velocity, \( f' \) the fuel consumed, \( t' \) the time in bad weather, Let \( h'' \) be the power, \( v'' \) the velocity, \( f'' \) the fuel consumed, \( t'' \) the time in good weather, Let \( h''' \) be the power, \( v''' \) the velocity, \( f''' \) the fuel consumed, \( t''' \) the time in bad weather,

Also, let \( k \) represent the consumption of fuel per horse-power per hour, and \( s \) the length of the voyage or distance performed. Then

\[ f = k h \frac{s}{v} \quad v = \text{a given quantity}, \] \[ f' = k h' \frac{s}{v'} \quad v' = \text{a given quantity}, \] \[ f'' = k h'' \frac{s}{v''} \quad v'' = \left( \frac{v'^2}{h''^2} \right)^{\frac{1}{2}} - v + v'^2 \] \[ f''' = k h''' \frac{s}{v'''} = k h' s \left( \frac{v'^2}{h''^2} - v^2 + v'^2 \right) \]

Putting \( f'' = u, h' = x, \) and differentiating, we get

\[ \frac{du}{dx} = \left( \frac{v'^2}{h''^2} - v^2 + v'^2 \right) - \frac{1}{2} v' \frac{h'}{h''} \left( \frac{v'^2}{h''^2} - v^2 + v'^2 \right) \]

whence by reduction, in the case of a minimum, we obtain the value

\[ x = 2 h = \frac{v^2 - v'^2}{v'^2} \ldots \ldots \ldots (A.) \]

Whence we obtain the very simple rule for finding the best proportion of power to tonnage: From the square of the velocity of any given vessel in good weather, subtract the square of the velocity of the same vessel in the worst weather; divide the difference by the square of the velocity in good weather, and the quotient multiplied into double the horse-power of the said vessel will give the power which would propel the same vessel in the same circumstances with the smallest quantity of fuel.

We have also from (A) \( h' = 2 h \frac{v^2 - v'^2}{v'^2} \)

(B) \( v'' = \sqrt{2} (v^2 - v'^2)^{\frac{1}{2}} \) (C) \( v''' = (v^2 - v'^2)^{\frac{1}{2}} \) (D) \( f'' = \sqrt{2} \frac{k h s}{v'^2} (v^2 - v'^2)^{\frac{1}{2}} \) (E) \( f''' = \frac{2 k h s}{v'^2} (v^2 - v'^2)^{\frac{1}{2}} \) (F) \( t'' = \frac{s}{\sqrt{2} (v^2 - v'^2)} \) (G) \( t''' = \frac{s}{\sqrt{v^2 - v'^2}} \)

It appears from the comparison of (B) with (C), that a vessel has its power in the most economical proportion to its tonnage on a given station, when its worst voyage does not exceed the time of its best in a greater proportion than \( \sqrt{2} : 1 \); that is, than 14 to 10, or 7 to 5.

From (D) and (E) it further appears that in a vessel, whose power is thus proportioned, the consumption of fuel in the worst voyage will not exceed that of the best voyage in a greater proportion than 10 to 7; that is to say, for 70 tons of fuel burned on a good voyage, it will not be necessary to carry more than 100 tons, in order to provide against the worst.

Let us take as an example a transatlantic steam-ship, which has a proportion of 1 horse power to 4 tons of capacity. Her unfavourable voyage being between England and America twenty-two days, and her favourable voyage fourteen days, being a comparative velocity of 7 and 11, then

\[ h' = 2 h \frac{v^2 - v'^2}{v'^2} = 2 \frac{121 - 49}{121} = 2 \frac{72}{121} = 12 \text{ nearly}. \]

Hence, the power of such a vessel should be increased in the ratio of six to five; that is to say, the engines at The following results are obtained:

The vessel of less power burns thirty tons per day, performs the distance in fourteen days, consuming 420 tons of coals in fair weather.

The vessel of less power burns thirty tons per day, performs the distance in twenty-two days, consuming 660 tons of coals, in foul weather.

The vessel of greater power burns thirty-six tons per day, performs the distance in twelve and one-half days, consuming 468 tons of coals, in fair weather.

The vessel of greater power burns thirty-six tons per day, performs the distance in seventeen days, consuming 630 tons of coals, in foul weather; being a consumption of sixty-four tons less fuel, and performing the voyage in four and a half days less than the other.

It is manifest that the store of fuel carried in the vessel with less power, must on all occasions be equal to the greatest consumption of fuel; that is, to at least 650 tons, whereas 630 tons will be sufficient for the vessel of greater power; and as in all vessels for long voyages, coals carried are much more costly than the mere price of coals, or as the freight of the vessel is more costly than the fuel, coals carried are to be reckoned at least as expensive as coals burned. Moreover, as the gain in time and in capital is four one-half out of twenty-two, being twenty-five per cent, it is plain that the vessel may be calculated to perform the distance oftener in a year; because as the times of starting must always be regulated, not by the shorter but by the longest period of a voyage, seventeen one half days in the one case, stand in the place of twenty-two days in the other.

As another example, let us take the case of a vessel calculated to stem the monsoon in the Indian seas. A vessel of 600 tons and 200 horse power, steaming in fair weather at the rate of eleven miles an hour, has been found to have her speed diminished by the monsoon to five miles an hour. What would be the best proportion of power in such circumstances?

\[ h = \frac{v^2 - v'^2}{v^2} = 2 \left( \frac{11^2 - 5^2}{11^2} \right) = \frac{16}{10} \text{ nearly.} \]

Hence we see that the power being increased in the ratio of sixteen to ten, that is, engines of 320 horse-power being substituted for those of 200, the speed on the quick voyage would be twelve three-fourth miles an hour, instead of eleven, the speed against the monsoon increased from five to nine miles an hour, with a saving of coals amounting to forty tons out of 320; and when it is remembered that the voyage for which eighteen days would be required as continual allowance in the one case, might always be calculated on as performed in ten days in the other, the advantage is placed beyond all doubt. It appears, therefore, that for long voyages especially, great advantages in point of economy, certainty, and speed, are to be obtained by the use of vessels of a higher power than usual; and that, in a given case, the best proportion of power to tonnage may readily be determined from the rules already given.

In regard to absolute or definite proportion, it may be stated as the result of the best vessels, that the proportion of power to tonnage should not be greater than one horse power to two tons; the greater proportion holding in the smaller, and the less proportion of power in the greater vessel.

The Proportions, Form, and Mechanical Structure of Steam-Ships.—In the article Shipbuilding, the reader will find the elements of construction of ships developed and applied in a satisfactory and lucid manner. There he will also learn, that naval architecture is scarcely recognised as a science in England. The reader will therefore be prepared for the announcement that the proportions and structure of steam-vessels is an enquiry which has hardly as yet systematically commenced; and it is with much hesitation that we set the example of endeavouring to eliminate from the rude mass of practical truth and practical error, some general results worthy of confidence. We may premise, that the drawing and finding the displacement, centres of gravity, and buoyancy, and the calculations of stability, &c., may be performed for steam-ships by the methods, and on the principles developed in the article to which the reader has already been referred.

The proportions of steam-vessels were originally taken from sailing vessels; the lengths being three or four times the breadth. Six breadths to the length is now a common proportion. The proportion of depth varies with dimension, being about one-half the breadth in vessels of 100 tons, two-thirds of the breadth in vessels of about 600 tons, and three-fourths of the breadth in vessels of 1500 tons. The qualities of a vessel depending much on its form, it is not possible to deduce a very precise rule for proportion abstracted from shape; but the following list of dimensions is deduced from a comparison of the dimensions of the best vessels, and will serve as a standard of reference for the existing state of practice. The following are dimensions of flush-decked vessels without poop or forecastle. Where these exist, the depth must be diminished so as to leave the mean depth the same. Thus, in the table, a vessel of 180 feet long by thirty feet beam, has twenty feet depth; but with a half-poop she would require to be only about eighteen one-half feet deep.

### Table of Dimensions of Sea-going Steam-Vessels of the best proportions, in conformity with the best practice in Britain.

| Length between the perpendiculars | Breadth between the paddles | Depth hold and midships | Tonnage, Old law | |----------------------------------|-----------------------------|-------------------------|-----------------| | 90 feet | 16 feet | 7 feet | 110 tons | | 96 | 16½ | 7½ | 118 | | 102 | 17 | 8 | 140 | | 108 | 18 | 9 | 168 | | 114 | 19 | 10 | 197 | | 120 | 20 | 11 | 230 | | 126 | 21 | 12 | 266 | | 132 | 22 | 13 | 306 | | 138 | 23 | 14 | 350 | | 144 | 24 | 15 | 397 | | 150 | 25 | 16 | 450 | | 156 | 26 | 17 | 505 | | 162 | 27 | 18 | 565 | | 168 | 28 | 19 | 630 | | 174 | 29 | 20 | 700 | | 180 | 30 | 21 | 776 | | 186 | 31 | 22 | 856 | | 192 | 32 | 23 | 941 | | 200 | 33 | 24 | 1044 | | 205 | 34 | 25 | 1136 | | 210 | 35 | 26 | 1231 | | 216 | 36 | 27 | 1240 | | 222 | 37 | 28 | 1455 | | 228 | 38 | 29 | 1576 | | 235 | 39 | 30 | 1712 | | 240 | 40 | 30 | 1838 | | 250 | 40 | 30 | 1923 | | 300 | 50 | 40 | 3590 | The form of the ship, of course, affects very materially its qualities, and the choice of proportions to produce those qualities. The dimensions in this table apply to vessels of fine proportions, having a fine entrance and run, and a side nearly upright. If however the area of the load-water line be very large, the vessel will be uneasy even with these extreme dimensions; and in such a case the beam in the table is rather excessive, while the height might probably be augmented without inconvenience. Again, if the midship section of the vessel be very square, or merely rectangular, these dimensions will suffice. If however the bilges be round, and the sides slope outwards, more breadth may be usefully employed, so as to leave the breadth at the load-water line nearly equal to, or rather greater than, the beam given in the table.

River steam-vessels are, in this country, and especially on the Thames, made of great length in proportion to beam. Some of the swiftest river boats have their length equal to seven, eight, nine, and even ten times their beam, with advantage. In America they often have twelve times more length than breadth.

The Form of Steam-Vessels.—To determine the best form of a steam-ship may appear to be a much simpler case of the great problem of naval construction, than the formation of a sailing vessel. The principal desideratum in a steam-ship being the power of going fast through the water in the single direction of the propelling power, this case of the problem appears to approach much more closely to the construction of a solid that shall receive the least resistance in passing through the water, than to the case of the sailing vessel, which has to work with a propelling power which is generally in some other direction than that in which the vessel is designed to make way. In this point of view, the problem of the steam-ship is really a simpler case of the general problem than that of the sailing vessel. If, however, the steam-ship is also to be a good sea boat, and to work on some occasions under canvas alone, as well as under steam alone at other times, the problem at once assumes an aspect more complex than that of either problem taken by itself.

There is, however, a single fact which is important, as it very much simplifies the subject. Vessels built expressly for the purpose of steaming, and adapted for that purpose in the best possible way, have been found, when under canvas, to equal the fastest ships in sailing qualities. Their great length and fine ends prevent them from falling to leeward; their fast formation adapts them for going through the water; their boilers and machinery form a well placed and well distributed ballast; their fine ends and flaring bows render them lively as sea boats; and the small amount of their midship section, and small resistance, give them great speed under comparatively little canvas. This practical fact, that a vessel formed exclusively for steaming, and adapted for that alone, in the best possible manner, is found to be a good and fast ship under canvas, greatly facilitates the enquiry concerning the best form of a steam-ship. To this we now add another confirmatory fact, that the fastest schooners, cutters, smugglers, yachts, and slavers, approach more nearly to the form of the best steamers than any other class of sailing vessels. The problem of the best form of a steam-ship becomes thus not only simpler, but doubly interesting, from the reflex influence it may be expected to produce on sailing ships.

It is difficult, without going into minute technical details, to explain the peculiarities in the shape of the best steam-ships. The present state of practice shows that systems perfectly opposite are adopted by different builders. It is at all times difficult to convert into ver-

bal statistics forms so delicate and complex as the surfaces of double curvature formed by the bottom of a ship; but the following considerations of a general nature may probably be intelligible.

In the formation of steam-ships, it has been stated that there are opposite schools. One adopts and advocates a sharp bottom, a great rise of floor, great beam, extensive bearings on the surface, round sides, round water-lines, adopting altogether the formation of a full, capacious, stable, sea-going ship, only employing such dimensions and proportions as are given in the table of dimensions already produced. Another school adopts a flat bottom, long floor, more angular bilge, upright sides, straight entrance, clean run, sharp ends, comparatively small moment of stability, formed with the idea of going directly through the water in all weathers with the least proportion of resistance, and the smallest change of position. A third school, of recent origin, adopts the hollow wave lines and new formation, of which the principles have been established by the writer of this article. The fastest steam-vessels of the present day are built on this principle.

The question of form may be taken up under several heads.

The Transverse Section, or Midships.—The simplest and one of the earliest sections of a steam-ship is the rectangle, fig. 26, the bottom being flat, the sides vertical, and the bilges almost angular. This form is rendered necessary when the breadth of the vessel over the paddles is to be rendered as small as possible. But this form, although it gives the greatest capacity when the breadth and depth of water are limited, is at once weak at the bilges, liable to crankness, and uneasy at sea. To remedy these evils, the bilges have been rounded, and the floor sharpened, in order to give more easy lines on the bottom, and an easier bilge, as in fig. 27.

Fig. 26.

And again, this method has been carried to an extreme, or with the intention of producing the best possible sea boat, by making the floor very sharp, and the sides extremely round, thus:

Fig. 28.

But such boats are both unstable at sea, and pitch most violently. The next modes of construction have had for their object to produce the greatest capacity with the least material, and least surface of adhesion to the water. For this purpose semicircular and elliptical bottoms have been tried, thus:

Fig. 29.

Fig. 30. But both of these, and especially the former, although well suited for fast steamers, have a great tendency to oscillate continually, and roll with great latitude at sea.

It appears from experience, that there is great difficulty in determining that section of vessel best suited to a steam-vessel. The rectangular figure first given is, as we have said, at once weak, and crank, and uneasy. The sharpening of the bottom, as in the figures which follow it, removes the engines up from the floor, and effectively diminishes the height of the engine-room, as well as renders the vessel crank, by raising the centre of weight, and of the engines, &c., too high; and if, to counteract this evil, the beam at the surface of the water be increased as in the third section, the vessel is rendered laborious, uneasy, and ineffective at sea by the excessive beam. Again, in the round bilges the vessel swings like a pendulum, and it seems as if her oscillating would never stop.

From the multitude of practical experiments which have come under our notice, we are led to the following conclusions:

1. That the existence of a fixed mass in the shape of engine and boilers, renders the usual mode of determining the midship section of a ship inapplicable to steam-ships; and that the form must be determined with immediate reference to these.

2. That the engines of a vessel of 300 horse power occupy a space of about \( \frac{1}{3} \) of the beam of a ship, which necessarily is perfectly flat; and that the engine can only be firmly connected with this floor of the ship by being placed as directly in contact with it as possible; and further, that the weight of the said engine must be placed as low as possible, on account of the place of the paddle-wheel; all of which desiderata can only be obtained by making the floor of the vessel parallel to the bottom of the engine.

Hence the bottom of the ship should be nearly flat across about \( \frac{1}{3} \) of her beam, thus:—B to B; fig. 31, nearly flat, EE the engines.

3. That no displacement is desirable on each side of the engines beyond what is required to give an easy turn to the bilge; for it is found, as indeed it should be expected, that all displacement on each side of the engines, at the lower part of the bilge, being vacant space, or very inefficient stowage-room, is not only wasted, but tends to impair the stability and sea-worthiness of the vessel; and, further, the engines being placed low, a species of stability of the most valuable nature is obtained.

4. That there are two ways of obtaining stability; one by having the weight of engines and boilers as low as possible, which is obtained by the means already described, and by depth in the water; the other by considerable beam. Now, beam in excess is one of the worst features of a steam-vessel. It produces a rolling oscillation, when the wind is in any degree on the beam, which impairs exceedingly the action of the paddles; it gives a species of roll, which is at the same time most distressing to passengers, and most injurious to the ship. All these bad effects are diminished, and can alone be corrected, by obtaining stability as far as possible from depth of the centre of weight rather than beam, according to the midship section already given.

The Water Lines.—Opinions on the subject of water lines, or on the degree and manner of fulness or fineness which the ends of a vessel should possess in reference to the middle, are as various as the deviations which one may conceive possible from any given shape. When with these we combine the differences of opinion concerning midship sections, which differences must also affect very materially the form of water line, we get steam navigation into a labyrinth of difficulties, in the intricacies of which the good qualities of a steam-ship are so often lost.

Full round ends, convex outwardly at the bow, full form of above at the stern, and fine enough below to steer well, so rendering the form as like as possible to an American cotton ship, with a long straight narrow body in the middle; such a form has been introduced for steam-vessels, in the hope that the vessels, by having a small midship section and great buoyancy, might be easily propelled through the water. Even when they are made seven times as long as broad, we have seen vessels of this class turn out failures. They have, in the first place, been crank, in the second place wet, in the third place slow, and in the fourth place weak; for, by having too much bearing at the ends, and too little where the chief weight is to be supported, viz. in the middle, they have invariably bent down in the middle, and risen up at the ends.

Full round ends, combined with a full round midship section, are a modification from which much has been expected, as forming a ship of large capacity. This has been one of the worst and most extensive errors perpetrated in the construction of large steam-ships. The great breadth along the whole water line, arising from the full lines, gives an excess of superficial stability, which, with a cross sea, causes the vessel to roll violently, with an extent and abruptness of motion which the round form of the section has no tendency to prevent or retard. Then the full ends of the vessel prevent her speed through the water, and increase her motion in a heavy sea, by increasing to excess her longitudinal stability. In the next place, if the ends of the ship be used for stowage, it is plain that the great mass of matter at the two ends must render the ship laboursome, or the reverse of lively, according to the nautical phrase; and the ship will less readily obey the helm. Such are some of the evils which, in many instances, and those especially in steam-ships of the largest class, have been seen to result, and which necessarily must result, from the full and round-bodied vessel used in steam navigation.

These are not all the evils of the full form. The stowage of such vessels is by no means effective in proportion to the weight, capacity, and displacement of the ship. In the first place, by giving much space on both sides of the engine-room, a very inferior species of stowage is obtained to that which results from additional length of hold. Next, the stowage-room in the end of the ship, for which so much speed is sacrificed, cannot be made effective without rendering the ship unseaworthy and unmanageable; for it is notorious, that in order to rectify the erroneous fulness for which so much is sacrificed, the ends of the ship are bulkheaded off to obtain the valuable quality of liveliness. First, then, fulness is obtained at a sacrifice of speed and seaworthiness for some supposed advantage in capacity, &c.; then, that very capacity is rendered ineffectual by the injudicious mode of its application.

An opposite school from this recommends the long straight centre body of a ship, with rectangular sections and sharp, fine, wedgelike ends. This form possesses the advantage of small transverse sections, and gives great stowage: it is an easy sea boat, and is lively from its fine ends. The principal fault in this form of vessel is its liability to crankness—its weakness at the bilge. Many of the finest steam-ships belong to this class.

The last class to which it is necessary to make a particular reference, are the steam-ships recently constructed on the wave-lines, or the hollow entrance line—on the principle which the writer of this article, by experiment and by example, has laboured to introduce. The Steam Navigation.

The first vessel of this form was an experimental one of 75 feet keel, laid down in 1834. The next was a steam-vessel of 100 feet keel, constructed in 1835. The next were two pleasure yachts of Mr Ashton Smith, a wealthy proprietor in Wales, whose observation on vessels had independently led him to the conclusion that hollow lines and a peculiar midship section gave the easiest and best sea steamers; and both of these vessels, of 1838-39, though merely approximations to the true wave-lines, were remarkable for their speed and other excellent qualities. The fourth vessel of this class was the Shandon steam-vessel, altered from the old to the new lines, 1840, with a gain from the same engine of from two to three miles an hour in speed. This vessel is the property of Mr Robert Napier. The next and last vessel is the Flambeau, built in 1840, on the wave principle, by Mr Duncan of Greenock, with the cooperation of the present writer. This vessel, with the smallest proportion of power to tonnage, and with the smallest supply of steam, is, nevertheless, by far the swiftest vessel on the Clyde. The Fire-king, the largest of this new class of vessels, is 660 tons, and has engines of 220 horse power. The Flambeau has only 70 horse power to 280 tons measurement. Vessels of this class have been found at sea to be both easy, stiff, dry, and lively; while they are by far the fastest vessels of their power. The speed of the Fire-king, now the property of Mr Robert Napier, is fifteen miles an hour in still water. The speed of the smaller vessel, the Flambeau, with very deficient steam, is fourteen miles an hour; a velocity which, with her small proportion of steam-power, is only to be attributed to her superior form, and the slight degree of resistance which she encounters from the water.

The principle on which these wave-ships are constructed is, that the hollow lines forming the entrance are to correspond, as nearly as may be consistent with the form of a ship, to the form of a certain wave capable of moving with the same velocity as the vessel. The analogy between the displacement of the water by a wave of the first order, and its displacement by a vessel moving with the same velocity, being so very close as to approach to identity, rendered it probable that the same mode of displacement would be followed in both cases with the same result, viz., the production of minimum resistance. It was further to be anticipated, that as a wave, when allowed to follow the usual mode of displacing the particles of water over which it passes, presents a smooth and unbroken swelling surface, so the vessel, if of the proper shape, according to these wave-lines, would divide the water at the bow in a smooth, unbroken sheet, instead of showing the usual head of water or surge exhibited at the bow of ordinary vessels at high velocities. On the other hand, when a wave encounters a shapeless rock, or breaks on a rugged coast, it exhibits the same violent surges which are presented on the bow of vessels of the usual form. Thus, then, the analogy leads us to suppose, that the smooth, continuous, resisting displacement of a wave, would be the best method of displacement for a vessel. On submitting the question of least resistance to the elementary calculation, it appeared that the form of least resistance was very close indeed to that of the wave. The science of hydrodynamics is not, however, sufficiently matured to enable us to place implicit dependence on all the results of its calculations, unless where they are supported by actual observation; and it therefore became necessary to make the experiment.

For the purpose of determining whether this form were that of least resistance, an experimental vessel, about seventy-five feet long, was constructed on a hypothetical form of least resistance, with the wave water lines. When this vessel was propelled at the rate of seventeen miles an hour through the water, it was found, that instead of the usual surge exhibited at the bow of other vessels, the water was parted so smoothly and quietly, that no white spray nor other symptoms of high speed and great resistance were visible, and the parted water returned peaceably to the place it had occupied previous to the transit of the boat, with only a slight translation forwards. It appeared, therefore, from the experiment, that no greater quantity of motion was communicated to the water than was necessary to permit the vessel to pass through, and with no greater velocity than the speed of the vessel demanded. It was then presumed that this form was that of least resistance; and all subsequent experiment appears to demonstrate the truth of this inference from fact, as predicted by analogy and calculation.

It is also worthy of remark, that this form is capable of being combined with all the good qualities of a steamship, such as strength, dryness, easiness, as well as great speed; but as the construction of such vessels may still be deemed an experiment in progress, the writer will not occupy more space with observations on his own researches. Thus much he felt it his duty to communicate, in order to adapt this article to the most recent condition of steam-navigation.

The immediate Mechanism of Propulsion.—The paddle-wheel of the ordinary form (as given in the plates) seems to be the most perfect, as it is the most simple means of propelling vessels through the water. The idea soon occurred, that as the steam-engine is calculated to turn round wheels, it is only necessary to place, on a wheel on the outside of a boat, large teeth or paddle-boards to take hold of the water, and so drive the vessel forward by simply turning the wheel. It was this plan that was adopted by Jonathan Hulls, in the first plan of a steam-vessel. But there is no piece of mechanism (if we except, perhaps, the crank of the steam-engine,) which has been more despised, or which more strenuous and frequent attempts have been made to improve or supersede, than the common paddle-wheel. It is remarkable, that like the crank steam-engine, the paddle-wheel is almost universally employed in practice, after the fullest experiment of many diversified improvements. In fact, after experiments of all sorts of oars, propellers, paddles, chaplets, screws, &c., the common paddle-wheel continues to predominate as "the propeller."

The numerous faults attributed to the common paddle-wheel, are chiefly faults of misconception or malconstruction. It is easy to account for both.

When a steam-vessel is at rest in a harbour, and prevented from moving, or when in the act of setting out into motion after having been at rest, the defects of the common paddle-wheel appear to be very great. The paddle-boards, fig. 32, on entering the water, press obliquely down into it, tending to raise or lift the vessel up out of the water with a force which produces no useful effect. Again, when the paddle is rising out of the water behind, it seems to do little more than raise or drive the water upwards in the form of back water. It is only, therefore, in the middle of its path that the propulsion of the paddle seems exerted in forwarding the boat, and that only for a very short time. A large part of the force of the steam-engine seems thus to be expended in raising up the vessel, and The parallel wheel, fig. 33, is constructed on this principle, "that if two equal circles be equally divided, and so placed, that the distance between two of the points of division is equal to the distance between the centres of the circles, then will all the other points of division be also equidistant, and all the straight lines joining them be parallel." By giving to each paddle-board revolution on an axis, and placing an arm at right angles to it, connected by a junction-bar with an eccentric strap around the axis, the geometrical problem is mechanically constructed; and we have Buchanan's parallel paddle-wheel. This wheel, with and without alterations in mechanical structure, has been invented and reproduced over and over again. It has always failed, being radically bad.

In truth, the phenomena of a paddle-wheel revolving on a steam-boat, when the vessel is in motion, differ essentially in their form and effects from the phenomena of a wheel revolving around a centre which stands still. When the vessel is only starting, or as yet moving very slowly, all the evils here mentioned do in some degree take place; but by the motion of the vessel forwards, which is the result of the revolution of the paddles, the evils complained of are at once remedied, and the paddle of a common wheel in a quick vessel is actually "feathered," according to the most dexterous toss of the practised rower. A little study of the geometrical conditions of a paddle moving forwards and in a circle at the same time, will make this plain. Let us trace for this purpose the motion of a single paddle. At the point \( o \), the paddle-board \( O' \) being in the position \( O' \); the

then, by the property of the cycloid, all lines drawn from the point \( M \) at the superior extremity of the vertical diameter of that circle to \( A, B, C, D, E, F, \ldots \), points in its circumference, will be parallel to the cycloid of progression, or rather to its tangents, at the points of its periphery which correspond to \( A, B, C, D, E, \ldots \), when in motion. If it were possible to construct this Steam Navigation.

Steam navigation presents a geometrical problem in a mechanical apparatus, this paddle-wheel would have great efficacy even when very deeply immersed. It is, however, difficult to make this motion perfect at M. But this species of mechanism has been very beautifully combined and arranged by Morgan, Seaward, Cave, and others, whose geometrical apparatus is very beautiful. Unhappily the apparatus, even in its most perfect state, is only correct for a single velocity of vessel and of wheel; for a different velocity, the point of radiation of the paddles must be changed, or loss is at once incurred. Hence it is found that this apparatus, like the common paddle, is liable to imperfections of action, with every change of immersion and velocity. When to this there are added the complexity, friction, cost, wear and tear, liability to accident, of this moving mechanism, introduced for obtaining the partial remedy or slight amelioration of an evil which by proper arrangement is but slightly felt under the old method, it becomes manifest, that the general abandonment of the radiating paddle-wheel, and the return to the common one, has not been without sound practical reason.

The last species of paddle-wheel is that with the fixed float; in other words, the simple paddle-wheel with boards placed around its rim. Of this there are various modifications. A very simple modification is that mentioned by Mr David Stevenson, in his excellent work on the civil engineering of America. The paddle-board of the usual wheel is, as it were, cut in two, one-half being placed half an interval in advance of the other, as in figs. 37 and 38. This may be called the divided paddle-wheel. The concussion of a paddle-wheel striking the water is much lessened by this means, and the propelling force is rendered more nearly uniform. Another form of this wheel may be named the split paddle-wheel, from having the paddle-board, as it were, split into two or more horizontal slips, by which the same advantage is obtained as from the divided paddle-wheel. It has been proposed to place these stripes in a cycloid; but no advantage results from the arrangement, although the dignified name of the cycloidal paddle-wheel has been applied to it. Again, it has been proposed to place the paddle-boards at all sorts of angles with the axis of the wheel, both horizontally and vertically, but as yet without advantage.

A very simple expedient tends to remove all considerable irregularity or concussion from the common paddle-wheel. It is to allow the extremity of the paddle-board nearest the side of the boat, to descend from six to twelve inches deeper in the water than the outer extremity. This plan was carried into effect by the writer on a steam-vessel in 1836. The desired object was attained without any sacrifice of power or speed. For distinction we may call this the conical paddle-wheel. It is shown in figs. 40, 41.

In the three following figures we have represented the single oblique paddle-wheel. Fig. 44 shows the development or stretch-out of a part of the circumference of the wheel, to exhibit more clearly the arrangement of the paddle-boards.

In figs. 45, 46, the double oblique paddle-wheel is represented; and in figure 47 the development of a portion of its circumference is given.

The Roofing Paddle.—One of the greatest improvements on paddle-wheels, and one of especial importance to steam navigation, still remains to be invented. We mean such a mechanism as shall enable the steam commander to set out on a long voyage deeply laden, with a small diameter of paddle-wheel; that is, with the paddle-boards near to the axis, and to increase the (effective) diameter of the paddle, that is, to remove the paddle-boards farther from the axis, as the vessel proceeds on her voyage and is lightened by the consumption of coal. The invention of a durable, economical, and safe apparatus still remains to be made. In the infancy of steam-navigation, Mr Buchanan of Glasgow published an account and drawing of a reeving paddle.

The following Table exhibits a comparative view of the Size and Power of six of the largest of the recently constructed Vessels for Transatlantic navigation.

| Name of Vessels | British Queen | President | New York | Great Western | Liverpool | Acadia | |-----------------|--------------|-----------|----------|---------------|-----------|--------| | Length from Figure Head to Tailrail | 275 ft. | 273 ft. | 235 ft. | 240 ft. | 234 ft. | 228 ft. | | Length of Upper Deck | 245 ft. | 243 ft. | 0 ft. | 0 ft. | 212 ft. | 206 ft. | | Breadth within the Paddle-Boxes | 40 ft. | 41 ft. | 36 ft. | 0 ft. | 35 ft. | 34 ft. | | Breadth over all | 61 ft. | 68 ft. | 60 ft. | 57 ft. | 58 ft. | 56 ft. | | Depth of Hold | 27 ft. | 30 ft. | 22 ft. | 29 ft. | 23 ft. | 22 ft. | | Diameter of Paddle-Wheels | 31 ft. | 30 ft. | 0 ft. | 0 ft. | 28 ft. | 28 ft. | | Diameter of Engine Cylinder | 6 ft. | 7 ft. | 0 ft. | 0 ft. | 6 ft. | 6 ft. | | Length of Stroke | 7 ft. | 7 ft. | 0 ft. | 0 ft. | 7 ft. | 6 ft. | | Power of Engines | 500 h.p. | 600 h.p. | 0 h.p. | 460 h.p. | 450 h.p. |

* The three other North American Royal mail steam-ships Britannia, Caledonia, and Columbus, are of the same dimensions as the Acadia.

DESCRIPTION OF THE PLATES ON STEAM-ENGINE AND STEAM NAVIGATION.

Plate CCCXLVIII. Figs. 1 and 2. These figures exhibit a front and side elevation of one of the simplest forms of the non-condensing steam-engine. Its principal parts are the cylinder A, the piston-rod P p, and connecting rod p K, acting directly upon the crank K X, and fly-wheel W W. Besides these there are only an eccentric and valve-rod x x x, and governor w w. Two columns and an entablature support one extremity of the crank axle, and give attachment to minor appendages. The other extremity of the axle rests on the wall of the building. To the columns is attached g g, a guide for the top of the piston-rod. The feed-pump f f is worked by an eccentric on the crank-shaft.

Figs. 3 and 4. The form of engine here exhibited, is of still greater mathematical simplicity than the last, although its mechanical arrangements are probably more intricate. In this engine no member intervenes between the piston-rod and the crank. A cross-head carried by the piston-rod, open in the centre, permits the crank-pin, in its circle of rotation, to oscillate freely on alternate sides of the piston; and being itself powerfully confined to motion in the vertical direction only, by the slides on the columns of the framing, the vertical motion of the piston-rod is precluded from the production of any other dynamical effect than the most direct of all possible conversions of rectilineal into rotatory motion. The cross-head is marked H H in the figure, the columns being marked m m. The other letters refer to the same parts as in the last figure.

Figs. 5 and 6. In these figures the high-pressure engine is represented in its most improved form for stationary purposes. It is analogous, in the arrangement of its principal parts, to the usual construction of Bolton and Watt's condensing-engine. A cast-iron base supporting six columns and an entablature, forms a framing upon which the parts of the engine are distributed, so as to form what is called a Portable Engine, being entirely independent of the building in which it may happen to be placed. At one extremity of the base is placed the cylinder A A, and at the other the crank-axle X, and fly-wheel W W. The motion is transferred from the piston P p, through the great lever L L L, and connecting rod or crank-rod L K. The feed-pump f f is in this instance worked from the point m of the parallel motion, in the way generally adopted in condensing engines for working the air-pump, whose place in fact it here occupies. The valve is a short D-slide, worked by eccentric gear, x x x. S is the steam-pipe. The education pipes E are seen descending on both sides of the valve-casing; they unite in a common chamber beneath the cylinder, whence a pipe conveys the condensed steam to the chimney, or to serve some other purpose, as the case may be. The governor acts as in the previous case. This drawing is taken from the form of engine manufactured by Messrs Caird and Company.

Figs. 7 and 8 is a form of the upright condensing-engine manufactured by Messrs Carmichael of Dundee, and successfully applied by them to various purposes. It is compact and has been found to work well.

The cylinder A A is placed upon the floor, and on either side of it stands a cast-iron column. These columns are hollow and are used as steam-pipes, S S S S, to convey the steam to the jacket of the cylinder, from which it finds its way into the valve-chest D. On the top of the columns is a cross-beam sustaining the crank axle, and the columns support guides m m m m, on which, by means of wheels g g, and a cross-head g p g, the piston-rod P p is maintained in its vertical position, so that the connecting rod p K is directly attached to the crank-pin K. The air-pump G is worked from the crank-shaft by means of a second crank or bend, and an eccentric x x works directly the slide valve; f f is the feed-pump for the boiler, worked directly from the air-pump cross-head; w w w w is the governor, with its appendages; C is the condenser; N the cold well.

Plate CCCCLXIX. In fig. 1 of this plate we have given a sectional elevation of a land-engine of twenty-five inch cylinder and five feet stroke. In fig. 2 we have given its horizontal section at the level of the base of the cylinder, and in the remaining figures the details of its Steam Navigation.

In figs. 1 and 2 AA is the cylinder, P the piston, PP the piston rod, BB the parallel motion, LLL the great lever. The pillow blocks LL, in which the centre of the great lever works, rest on the spring beam UU, whose ends are secured to the walls of the building in the manner shown on the next plate. The centre of the spring beam is sustained by the columns VV and their entablature W, which crosses the building and has its ends secured to the walls like those of the spring beams. At the other end of the great lever are the connecting rod LK, the crank KX, and fly-wheel WW. Returning to the cylinder we have, DD the slide-valves and their casing; dd the packing ports. The valve-casing terminates below in EE the eduction-pipe leading into the condenser C. G is the air-pump, F the place of the foot-valve, h the air-pump piston-rod. The condenser and air-pump with their appendages are placed in the cold well N. M is the hot well into which the contents of the air-pump are discharged, and from which the hot water pump m draws its supply by the pipe m'. The pipe oo leads from the hot water pump for the supply of the boiler. The cold well is supplied from the cold water pump n by the pipe n'. The rods for working the hot and cold water pumps hang from a stud at either side of the lever at m. The governor ww is supported on a bracket u, which bridges across the main shaft. The influence of the governor is conveyed to the throttle-valve by the levers and connecting rods rrww. The valves are worked by the eccentric xxx. ff is the eccentric shaft which carries the gab-lever j' on which the eccentric rod acts; it also carries the levers for working the side rods of the valves, the levers which carry the counterbalance weight, and the socket for the starting lever. The small pillars TT, which surround the cylinder, are surmounted by an entablature which serves as a support for a gangway round the cylinder.

The remaining figures on the plate represent in detail the different parts of the engine which we have just described, separated from each other, in order more clearly to exhibit their construction. Figs. A A' a' show the details of the cylinder. In A A' is shown the upper and lower ports of the cylinder at 1 and 2, and the steam port at 3. In A', 4 is the cylinder cover, and 5 the stuffing box. a is a horizontal section of the cylinder, and a' a plan of the cylinder cover.

Figs. DD' dd' show the slide-valve casing; D a front view, D' a side view. 1 and 1 are the packing ports, 2 and 2 the packing-port covers, 3 the eduction-pipe, d the cover of the slide-valve casing, 4 its stuffing-box, d' a section of the casing. Figs. C, G, F, show a side elevation of the condenser, foot-valve, and air-pump; C', G', F', a section of these; and c, g, f, a plan of them. 1 is the cover of the foot-valve, 2 and 3 a section and front view of the valve. Fig. L shows a side view of the great lever, L l a top view, and L 2 a transverse section through the centre of it. Figs. KK' show a front view and section of the crank. Figs. XX show a side view, an end view, and a plan, of the crank shaft pillow block. Figs. 1, 11, 12, show a side view, an end view, and a plan of the pillow block for the main centre of the great lever. Figs. mm show a vertical and horizontal section of the hot water pump, and figs. nn' of the cold water pump. Figs. B 1, 2, 3 are the details of the main links of the parallel motion; b 4, 5, 6, 7, 8 details of its air-pump links; 9, 10, 11, 12 side and top views of its radius and parallel bars. 13, 14 is the clutch for the top of piston-rod; 15, 16, gudgeon and clutch for the top of air-pump rod; 17, 18, top and side views of the ring gudgeon to which the parallel rods are attached; P piston-rod, H air-pump piston-rod, h air-pump rod, gg cold water pump-rod and piston-rod, and gg' hot water pump-rod and piston-rod; x the eccentric, WW, 1, 2, 3, 4 details of the fly wheel, main centre or gudgeon for the great lever. PP 1 plan and section of the piston, w w' 1, 2, 3, 4, 5 details of the governor, w the spindle, w' the slide, l l the radius arms to which the balls 5 5 are attached, 2 2 the radius arms which cause the balls to act on the sliding collar w', 3 and 4 the stay for confining the motion of the balls, t 1 2 is the slide-valve rod and side rods, t 3 is the slide-valve cross-head, R R' a side and front view of the connecting rod.

Plate CCCCLXXI exhibits a Sectional Elevation of a Condensing Engine. This description of house engine is the design of Mr McNaught of Glasgow, and has been extensively applied by him to cotton, silk, and saw-mills. The principal peculiarity in its structure is the arrangement by which no further masonry is required for its foundation than the building in which it stands, the usual cold well being dispensed with, and the whole structure connected by cast-iron beams with the walls of the house. The cylinder AA is attached immediately to TT, the cast-iron beams of the floor, which are deeply bedded in the wall at T and T, and rests directly upon the large vessel C, which forms the condenser, and is supported likewise by beams YY, which are bedded in the walls. The condensation is effected by injection alone, without the usual accompaniment of a cold well around the condenser, an appendage that may safely be regarded as by no means dispensable to the practical perfection of the vacuum—when the vessel itself is formed with few joints. The transverse beams of the buildings are supported by two pillars directly under the centre of the great lever LLL, so as to support the main centre L; and the crank-axe X and the axis Z of the fly-wheel W, are supported on UU, another beam of cast iron.

The steam enters the house through the pipe SS, passes round the cylinder to SS, around the long slide-valve DD; being confined to the middle of it by the valve packing hh, and after performing its duty in the cylinder, passes out at EEE into the condenser C, where it is finally condensed into water. Hence it is drawn off at the foot-valve F by the piston H of the air-pump G, and delivered by the discharge-valve M into N, the hot well. The slide-valve DD is worked by the eccentric gear xxxxx and the rod dD through a moveable stuffing-box dx.

Plates CCCCLXXII, CCCCLXXIII. These plates represent the high-pressure engines which are employed to work the inclined plane at the Liverpool station on the Liverpool and Manchester Railway. They are beautiful and in many respects highly judicious; they are the work of Messrs Mather, Dixon & Co., Liverpool.

WWW, Plate CCCCLXXIII, is the great wheel which works the rope that draws the railway train up the inclined plane; the rope is contained in a groove in the edge of the wheel. A clutch kk connects or disconnects the crank-axe XXX with the wheel WW; the cranks KX, KX, KX are placed at right angles, so that when one is on the centre the other is at the furthest distance from it. Kk, the connecting rod, hangs down from LL, the ends of the levers. The centre of the side levers, IV., rests on a truss at no greater height than three feet above the floor of the engine-room. Lp is a side rod by which the levers are united to the cross-head rpr. The steam in this instance comes about a quarter of a mile from the boilers to the cylinders AA by the steam-pipe SSS. Fig. 2 is a section of the steam-valves and cylinder. The valves DD are short D-slides, surrounded by steam, and by the underside of the valves the escape takes place through the space E; dD is the valve-rod moved by the usual valve-gear xxx. The eccentric xxx, Plate CCCCLXXI., is placed on a long shaft from the

This lesser crank, just as by an eccentric. This gearing Steam Na- has the advantage of lightness and precision. m m are the usual links of the parallel motion; d is a counterpoise to the weight of the valve, w w are the weights of the governor.

Plate ccccxxlv. This is one of that class called the rotatory steam-engine; a class comprehending many varie- ties, of which we hear much and see but little. The en- gine is here given as an illustration of this very unsuc- cessful class of engines, by one of its least exception- able examples. It has actually been in use for some years, being frequently employed to turn the machinery of a large establishment. We have seen it working smoothly and well. Yet we have not been able to recog- nize in it any reason for giving it an equality, much less a preference, in comparison with the common engine. It can be reversed in the same way as a common engine. It was invented by Mr Yule of Glasgow, by whom it was patented, and is still in the works of Thomas Edington, Esq., at Glasgow.

SSS is a double steam-pipe, either branch of which may be employed according as the engine is to go forward or backward. AA is the cylinder firmly fixed on a stone foundation, and in its centre is an axis XX, upon one side of which and eccentric to the cylinder is an inner cylin- der or barrel turned quite true, and fixed to revolve with the axis X, and so to form the piston P, which is to receive and give out the force of the steam. RR furnishes the point d'appui, the surface of reaction, which resists the force of the steam and forms a fixed obstacle. It is a flat slide or sluice, (see fig. 5,) resting on the barrel piston P, and maintained by guides always in a vertical posi- tion. It passes into the cylinder through a rectangular stuffing box, and is raised and depressed by a small ec- centric pin xx, so as to remain always upon the surface of the piston drum. All the working surfaces are ren- dered steam-tight by metallic packings. EEE is the eduction passage into the condenser or the open air, DD are slide-valves to be reversed when the engine is to go backwards. On the revolving axis of the piston X are toothed wheels, gg, working other two, gg', which have a common axis zz, carrying a fly-wheel, and driv- ing the machinery to be worked by the engine. Fig. 6. shows the ports at DD. Fig. 7 shows the guides of the slide RR.

Plates cccclxxvii, cccclxxxviii, cccclxxix exhibit views of a pair of beautiful marine engines, constructed by Mr Napier, for the four British and North American royal mail steam-ships Britannia, Acadia, Caledonia, and Columbia, plying between Liverpool, Halifax, (Nova Scotia) and Boston, (U.S.) The following are the general dimensions of the vessel and engines.

| Length from figure-head to taffrail | 228 | | Length of keel and fore-rake | 206 | | Breadth of beam between paddles | 34 6 | | Depth of hold | 22 6 | | Diameter of paddle-wheel | 28 | | Length of floats | 26 | | Diameter of cylinder | 6 | | Length of stroke | 6 10 |

The power of the engines is about 240 horse power. The paddle shafts make 16 revolutions per minute. The tonnage of the vessel by the old law is about 1200 tons.

Plate cccclxxvii is a side elevation of one of the engines.

Plate cccclxxxviii is the elevation of the crank end of the engines, and Plate cccclxxix the elevation of the cylinder end. By an inspection of these engravings it will be seen, that the parts of the engines are sus- Steam Navigation.

Steam engines are constructed in an elegant and rigid Gothic framing, rendering them, notwithstanding the ponderosity of their different parts, entirely independent of the vessel on which they are placed. AA are the cylinders, B the slide-valve casing, C the condenser, D the hot well and air-vessel placed on the top of the condenser. E the air-pump, FF the feed-pumps. The moving parts of the engine are as follow:—K the cylinder piston-rod, I the cross-head, H the cylinder side rods descending to the great side levers GGG. Connected with the parts last described are the radius rods of the parallel motion L, the motion side rod Lt, and the parallel motion shaft l, V the valve or weight-shaft on which is fixed the valve lever W, whose other end is inserted into a clutch on the slide-valve link e. On either side of the centre of the great lever depends a side rod ff, to work the bilge and brine pumps, and to its extremity are attached the links of the cross-tail of the connecting rods, P the links, Q the cross-tail, R the connecting rod. To the upper end of the connecting rod is attached the crank S; T is the intermediate or crank-shaft, TT' the paddle-wheel shafts. On the crank-shaft is placed the eccentric U; and uu is the eccentric rod working the eccentric gat-lever v on the valve or weight-shaft ttt. Y yy are the expansion valve apparatus, h escape valves at top and bottom of cylinders, X paddle wheels, k lever for starting the engines, 1 steam-pipes, 2 waste water pipes from hot well, 3 double force-pump for filling boilers, extinguishing fires, and washing decks, 4, 4, engine beams, 5, 5, 5 midship section of vessel, 6, 6 thick planks checked in upon and bolted through the timbers thus:

Plate cccclxxx. Side and end elevation of one of the engines of her Majesty's mail packet, Urgent, and also of the Acteon, built by Messrs Caird and Company of Greenock. The Urgent plies between Liverpool and Dublin; the Acteon between Liverpool and Glasgow. Both vessels have been very successful: they are swift boats, and consume a small amount of fuel. Their general dimensions are here noted.

| Urgent | Acteon | |--------|--------| | Length of keel and fore-rake | 172 ft. | 171 ft. | | Breadth within paddle space | 26 ft. | 25 ft. | | Depth of hold | 17 ft. | 17 ft. | | Diameter of paddle-wheel | 24 ft. | 6 ft. | | Length of floats, which in the Urgent are of Galloway's patent, in 3 breadths of about 9 inches each | 8 ft. | 10 ft. | | Diameter of cylinder | 5 ft. | 2 ft. | | Length of stroke | 5 ft. | 9 ft. |

The power of each of the engines is 140 horse power. The paddle-shaft makes about twenty revolutions per minute. The tonnage of the Urgent, by the old law, is 5625 tons; of the Acteon 5518 tons.

AA is the cylinder, C the condenser, E the air-pump, H the cylinder side rods, I the cylinder cross-head, B the valve-casing, W the valve lever, WW the back balance, GGG the side levers, P the cross-tail links, Q the cross-tail, R the connecting rod, S the crank, U the eccentric, N the air-pump side rods, M the air-pump cross-head.

Plates cccclxxxi, cccclxxxii, cccclxxxiii, represent the engines of the Achilles, also built by Messrs Caird and Company, to ply between Liverpool and Glasgow. Plates cccclxxxvi, cccclxxxvii, show the two side elevations of one of the engines; and plate cccclxxxviii a section of the vessel to a lesser scale, with the engines, paddle-wheels, &c., in situ. The arrangement of the framing of these engines is highly beautiful. The entablature supported by the columns, uniting both engines in one design, gives massiveness of appearance, as well as great strength to the structure. In plate cccclxxxviii is seen the apparatus for working the engines expansively. On the crank axle T is placed a series of cams, ttt, which act upon the roller of the expansion-valve tumbler. Y yy are the expansion-valve connecting rods and levers. Z is the valve-chest, and the valve is of the kind called equilibrium valves, or crown valves. The other parts are A the cylinder, B the valve-chest, C the condenser, D the hot well, E the air-pump, F the feed and bilge pumps, GG the great lever, G its main gudgeon, H the cylinder side rods, I the cross head, K the piston-rod, LL the parallel motion, M the air-pump cross-head, N the air-pump side rods, O the air-pump piston-rod, P the connecting rod cross-tail links, Q the cross-tail, R the connecting rod, S the crank, U the eccentric pulley or cam, u u u the eccentric rod, V the valve-shaft, WW the valve-lever and counter balance lever.

Plates cccclxxxiv, cccclxxxv, cccclxxxvi. The engines exhibited in these plates are a pair of 110 horse power each, constructed by Messrs Fawcett, Preston & Co. of Liverpool.

Plate cccclxxxiv shows the side elevation of one of these engines. Plate cccclxxxv shows the elevation of the crank end of both engines; and plate cccclxxxvi the cylinder end of the engines, drawn to a somewhat smaller scale. The letters refer to the same parts as in the engines already described, and it is unnecessary here to repeat the description.

Plate cccclxxxvii. In this plate is given a representation of a single marine engine of 65 horse power, with a stroke of four feet. Fig. 1 is a side elevation; fig. 2 a plan or bird's-eye view; fig. 3 an elevation of the cylinder end; and fig. 4 an elevation of the crank end. The same letters indicate the same parts as in the former figures.

Plate cccclxxxviii, fig. 1, is an end view, and fig. 2 a side view, of a double towing-engine of forty-five horse power and three feet six inches' stroke. The most striking peculiarity of this engine is, that the paddle-wheel shaft is separate from the crank-shaft, and driven by it through the intervention of toothed wheels. T is the cranks haft, with its spur wheel driving the spur wheel of the paddle-shaft T'. The other letters refer to the same parts as before.

Plate cccclxxxix. In this plate are represented two engines of direct connexion, constructed by Messrs Tod and McGregor, Glasgow.

In figs. 1 and 2 of this plate, the crank S of the engine is placed directly above the cylinder A; the piston-rod K carries a cross-head I, which is guided to move in the vertical direction by two cross guides gg, one at each extremity, whose ends slide upon the vertical pillars pp, which sustain the framing for the support of the crank-axle. From each end of the piston cross-head depends a side rod HH, whose lower extremity, together with the ends of the side rods PP, which depend from the cross-tail Q of the connecting rod R, are attached to the end of a side lever GG. To the opposite end of the side levers are attached the side rods N of the air-pump, and on either side of its centre the side rods of the feed and bilge pumps F. The parts not already described are aa the slide-valve, C the condenser, E the air-pump, S the crank, U the eccentric, and uu the eccentric rod and valve-gear.

In the engine represented in figs. 3 and 4, the pi...