STEAM ENGINE. large size and especially sturdy construction. The largest stationary steam engines now used in any form are those employed for driving the generators of electric power plants. These large machines are almost universally of the inverted vertical direct-acting type, illustrated in the accompanying plate. A sixth important form of steam engine is the steam-driven air compressor described in the article AIR COMPRESSORS. Engines other than stationary fall into one of two great classes, viz., locomotive engines for railways and marine engines for ship propulsion. The traction engine is essentially a locomotive engine designed to run on common roads, and the portable engine is practically a stationary engine and boiler plant of small size mounted on wheels so that it may be hauled from place to place. The growth and construction of the locomotive engine are described in the article LOCOMOTIVE. Marine engines fall into two separate classes. For paddle-wheel boats the beam engine and the inclined engine are universally employed. For screw-propelled vessels the inverted vertical direct-acting engine is almost universal. (See STEAM NAVIGATION.) For a discussion of the theory of steam engines and heat engines in general, see STEAM and THERMODYNAMICS. For descriptions of special applications of steam engines, see AUTOMOBILE; FIRE-ENGINE; BLOWING-MACHINES. BIBLIOGRAPHY. For an account of the development of the steam engine, see Thurston, Growth of the Steam Engine (New York, 1879). Among the best theoretical and descriptive works are: Clark, The Steam Engine (London, 1890); Thurston, Manual of the Steam Engine (New York, 1892); Hutton, The Mechanical Engineering of Power Plants (ib., 1897); Seaton, A Manual of Marine Engineering (ib., 1895); Peabody, Valve Gears for Steam Engines (ib., 1892). STEAMER DUCK, LOGGERIHEAD, Or RACEHORSE. A very large duck (Tachyeres cinerus), numerous about the southern extremity of South America, so called on account of its peculiarity of rowing itself along the surface of the water at great speed. This is said to be due to the remarkable fact that this bird loses its power of flight when it reaches maturity. STEAM HAMMER. See HAMMER. STEAM HEATING. See HEATING AND VENTILATION. STEAM NAVIGATION. The Spaniards assert that as early as 1543 Blasco de Garay made an attempt to propel a vessel by steam in the harbor of Barcelona. In the absence of direct proof of the fact this may well be doubted. At the time mentioned the most advanced scientists in Europe had not yet begun seriously to consider steam as a source of power. The assertion is also made that Denis Papin (q.v.) in 1707 propelled a boat by steam on the River Fulda. Papin invented the safety valve and a single-acting steam cylinder pump, and made various improvements in steam pumps, but it does not appear that he ever built what might be called a steam engine. The boat which has been mentioned and which is frequently referred to had some sort of paddle wheels, but they were operated by the crew and not driven by steam In 1729 Dr. John Allen took out a power. patent in England for a method of propelling a 529 . STEAM NAVIGATION. boat by means of forcing water out of the stern with steam or other pressure. In 1736 the rather vague ideas of Allen were improved upon by Jonathan Hulls, a clockmaker of Campden, Eng HULLS BOAT. (From an old drawing.) land, and he was granted a patent for mechanism to propel a boat by steam power. Like Allen, he apparently made no serious attempts to put his ideas into practice. In 1752 the French Academy of Sciences awarded a prize to the distinguished physicist Daniel Bernoulli for an essay on the manner of propelling boats without wind. In addition to other suggestions he proposed the use of the screw propeller. Up to this time successful steam navigation was impossible because a practical steam engine did not exist. This deficiency was supplied by Watt, who took out his first patent in 1769, but the engines contemplated were really singleacting pumps. In 1782, however, Watt brought out the double-acting engine, and developed the principle of expansive working by cutting off the steam at a suitable point instead of allowing it to follow full stroke. All the conditions for the propulsion of vessels by steam were now in existence and experimental boats rapidly appeared. In 1783 the Marquis de Jouffroy built have been successful; but before it could be deone which was tried at Lyons, and it is said to lution overtook and ruined him. At the same veloped into a form for practical use the Revotime John Fitch, James Rumsey, and Oliver Evans were experimenting in America. Rumsey's boats, like the proposed vessel of Dr. Allen, were fitted with jet propellers, whereby a stream of water was discharged by a steam-driven pump. His first boat was tried in Virginia in 1784 and a second, which attained a speed of 4 knots, was completed in 1786. He died in London in 1792, just previous to the trial of a new boat built from his. plans. Fitch's boats were fitted with various types of propelling machinery -with paddle wheels in 1785 and afterwards with long paddles which were given motion similar to that of the paddle of an Indian canoe. In 1790 one of Fitch's boats attained a speed of 7 knots, and afterwards was used on the Delaware to carry passengers. In 1793 Fitch went to France; in 1796, after returning to America, he built a small screw steamboat, but the exact measure of success that he attained is uncertain. Evans experimented with various peculiar types of steamboats, one of which was fitted with a rude screw and wheels with which to run on shore. In England Joseph Bramah obtained a patent in 1785 for propelling vessels by means of "a wheel with inclined Fans or Wings similar to the fly of a Smoke-jack or the vertical sails of a windmill." A patent for a similar invention was issued to William Lyttleton in 1784 and to Edward Shorter in 1800. In 1791 John Stevens of Hoboken, N. J., patented a multitubular steam boiler, and he soon after began experiments with steam propulsion of boats, in which he was assisted by the celebrated engineer Mark Isambard Brunel, then an exile. Brunel left the United States in 1799, however, and it was not till three years later that Stevens completed a small screw-propelled boat which he used for his own pleasure. This little boat, only twenty-five feet in length, was the first successful screw-propelled craft built. Engines suitable for large screw steamboats were not yet invented, so that commercial success in this direction was not yet aimed at. Patrick Miller, a retired banker of Edinburgh, for several years experimented with boats of various types in a lake on his estate of Dalswinton in Dumfriesshire. These boats had two or three hulls con MILLER'S BOAT. nected by a flying deck and driven by paddle wheels placed in the space between the hulls. In the earlier experiments men were employed to turn the wheels, but in 1788, partly at the instance of James Taylor, a tutor in his family, Miller engaged a Scotch engineer by the name of Symmington to fit the boats with steam power. A small boat was tried and gave such promises of success that a larger one was built in 1789. In October of that year this boat attained a speed of seven miles an hour on the Forth and Clyde Canal. Either because of lack of interest or of means, Miller ceased thereafter to interest himself in the matter and nothing further was attempted. But in 1801 Symmington was commissioned by Lord Dundas of Kerse to build a steamer for towing barges on the Forth and Clyde Canal. This was the celebrated Charlotte Dundas. She was a success in CHARLOTTE DUNDAS. all essential respects, but the proprietors of the canal refused to use her because they feared the effect of the wash from her paddles on the banks of the canal. She was therefore broken up and her disappointed designer turned his attention to land machinery. The next development was Robert Fulton's Clermont, and her advent marks the beginning of steam navigation as a commercial success. In 1797 Fulton (q.v.) went to Paris from England and soon afterwards began experiments with submarine torpedoes and torpedo boats. About the year 1801 he secured the assistance of Robert Livingston, then the United States Minister to France, and they built a small steamboat. Her engines proved to be too heavy for the poorly constructed hull, which collapsed and sank. The engines were recovered, however, and placed in a larger boat 66 feet long and 8 feet broad, and on August 9, 1803, this boat was tried on the Seine, but the speed obtained was unsatisfactory. In 1804, as the agent of Livingston, Fulton went to England, where he ordered of Boulton and Watt the machinery for a much larger vessel which was to be built in the United States. In the autumn of 1806 Fulton returned to America, and the new engine followed him almost immediately. A hull, built in New York, was launched early in 1807, the engines were placed on board, and on August 7, 1807, the Clermont started on her trial trip. She proceeded without stopping to Clermont, the home of Livingston, on the Hudson, 110 miles away, and twenty hours later went on to Albany. The next day she started to New York and made the trip in thirty hours at an average speed of 5 miles an hour. Within a month she began to run regularly between Albany and New York. In The success of paddle steamers for sheltered waters was now assured, and they multiplied rapidly, particularly in the United States, where the conditions were particularly suitable. Great Britain the use of steamers was less immediate. The first commercially successful one to be completed there was the Comet, built by Henry Bell in 1811-12. She went into service on the Clyde and was soon followed by others. In the meantime the use of steamers for ocean navigation was being tried. In 1813 Fulton began the war steamer Demologos (see UNITED STATES, section on Navy), which was the first steam war vessel as well as the first ocean going steamer. Several steamers began to make regular trips along the British coast in 1818-19, but the voyages were all short. In 1819 a vessel fitted with steam power crossed the Atlantic. This was the Savannah, of 350 tons, with a length of 100 feet, which crossed from Savannah to Liverpool in 25 days. In her, however, the engines were purely auxiliary; she was fitted with full sail power, and when the wind was fair or the seas too boisterous for steaming the paddle wheels were unrigged and taken in on deck. The beginning of real transatlantic voyages under steam was made by the Sirius and the Great Western. The latter was built for transatlantic service and was the larger and more powerful, while the former was taken from the London and Cork line. The Sirius started on April 4, 1838, and the Great Western four days later. They arrived in New York within twenty-four hours of each other, the Sirius at 10 P. M. on the evening of April 22d and the Great Western the next afternoon at three o'clock. The average speed of the Sirius was 161 miles per day-the highest 220 miles and the lowest 85 (half day only); the amount of coal consumed was 450 tons. The Great Western averaged 208 miles per day and her highest run was 247 miles. Neither vessel carried much sail. For two or three years the transatlantic. steamer service was rather irregular. The Sirius was withdrawn after making a few trips, and though the Great Western continued running, she lost money for the company that owned her. Other steamers made a few trips, but they also, like the Sirius, were withdrawn. In 1839 Samuel Cunard, of Halifax, N. S., went to England and succeeded in forming the celebrated Cunard Company. Assisted by a liberal Government mail subsidy, it was commercially successful from the start. The first vessels put in service were the paddle steamers Britannia, Acadia, Columbia, and Caledonia. They were of 1154 tons burden and their machinery was of 740 horse power. The Britannia, the first to sail, left Liverpool on July 4, 1840, and made the passage to Halifax in 12 days 10 hours; on her return voyage she did better, the time being but little over ten days. The Cunard Company enjoyed a practical monopoly of the transatlantic service until 1850, when the Collins (American) and Inman lines were started. The Collins Line lost two of its four steamers and was discontinued in 1858. Two other American steamship lines were started in 1850, the New York and Havre Steamship Company and the Vanderbilt Line. Both ceased running at the beginning of the Civil War. The Inman Line was more successful. It began its career with steamers built of iron and propelled by screws. Though no faster than the wooden paddle-wheel Cunarders, they were cheaper to operate. The screw propeller (q.v.) now began rapidly to displace the paddle wheel, though the Cunard Company launched the Scotia, their last and finest paddle steamer, in 1861. The rapid increase in size of ocean steamships led to the production of the Great Eastern (q.v.), but she was half a century ahead of the demands of ocean traffic and the adequate development of marine steam engineering. She was fitted with both screw and paddle engines, as it was thought im possible for either separately to deliver sufficient propulsive effect. The combination was not an economical one, and was a leading cause of her failure as a commercial venture. By 1860, in the fight for supremacy, the screw had become the unquestioned victor over the paddle wheel so far as ocean navigation was concerned, both in the merchant marine and in naval construction. Its advantages for war vessels were numerous, but the greatest of these was the possibility of placing all the propelling machinery of a screw steamer below the water line; and this alone was decisive. In merchant steamers the advantages of the screw were of a different kind. The efficiency of the paddle wheel depends upon the depth of immersion of the pad dles; if too great or too little, the losses from slip, drag, and churning of the water are serious. The variation of draught consistent with economical propulsion was therefore very small-too small to admit of heavy loading. Very large wheels and feathering wheels reduced the losses somewhat, but introduced troubles of another type, while the rolling of paddle steamers in heavy seas greatly interfered with their speed and economy no matter what the character of the wheels. The draught and condition of lading of screw steamers was of much less importance and could be varied within much wider limits without perceptible loss of efficiency; rolling STEAM NAVIGATION. produced little effect, and though pitching might be serious in short vessels in which the screw was not deeply immersed, yet, owing to the small ordinary angle of pitch, the screw rarely rose high enough above the surface to give trouble. Up to this time boilers were of the box type and the pressure of steam carried rarely exceeded 25 pounds per square inch-in many of the early steamers 10 pounds or less was the common practice. But the displacing of box boilers by cylindrical permitted a higher steam pressure, and this in turn demanded another form of engine to utilize it economically. The compound engine, which was built and patented by Hornblower in 1781 and revived by Woolf in 1804, had not been much used, because the conditions had not demanded it; but now it became a necessity. It consisted at first of two cylinders-and many compound engines are still so built-in which the steam was expanded in two stages, the first expansion taking place in the high-pressure cylinder, by which the pressure was reduced one-half, more or less, and the second expansion in the low-pressure cylinder, where the pressure was carried down to the atmospheric line or below it. The demand for increased speed led to higher steam pressure and greater engine speed. The range of economical expansion in one cylinder being limited, the tri-compound or triple-expansion engine was designed to utilize the increased boiler pressures. The gain was twofold. The new engines, using a higher pressure of steam, were lighter than their predecessors of equal power and they were also more economical. The first large vessel to be fitted with them was probably the Propontis, which, in 1874, was supplied with engines designed by Mr. A. C. Kirk. By 1880 the use of triple-expansion engines became common, though compound engines were largely used for another decade and they are still fitted in certain steamers where the conditions favor their economical working. (See The continued demand for increased power, particularly in small vessels (torpedo boats and the like), naturally pushed up the steam pressure again, and, although the locomotive boiler was used to some extent, the advantages of the water-tube boiler soon became apparent. section on Boilers below.) Its capability to furnish very high pressure steam reacted upon engine design and produced the quadrupleexpansion engine. The water-tube boiler is not yet much used in the mercantile marine, but is rapidly displacing the cylindrical boiler in naval construction. It has not yet brought about the extended use of quadruple-expansion engines in large vessels, but this may follow in the course of time. The length of the voyage and the vast amount of traffic has caused the transatlantic trade to be the principal field of steamship development. While the gain in size and speed of the vessels in this trade has been continuous from the start, a great impulse was given by the building of the Britannic and Germanic for the White Star Line in 1874. They at once reduced the average passage from Queenstown to New York to about eight days. They were followed in 1879 by the Arizona of the Guion Line, confessedly built to outstrip all competitors, and her success was the begin |