354: STEAM NAVIGATION ran steamers from Newport, R. L, to Provi- dence and to New York. In 1825 the steamer Enterprise went to Calcutta from England, and in 1836 it was proposed to establish lines of steam vessels between New York and Liverpool. In 1838 the Sirius, a ship of 700 tons and 250 horse power, sailed from Cork, April 4; and the Great West- ern, a comparatively powerful steamer of 1,340 tons, 236 ft. in length, with engines of 450 horse power, paddle wheels 28 ft. diameter and 10 ft. length of floats, sailed from Bristol April 8. Both vessels arrived at New York April 23, the Sirius in the morning and the Great "Western in the after- noon. At this time Ericsson, Smith, and others were again ex- perimenting with the screw, and Ericsson soon brought it into general use in the United States. His first boat was successful as a tugboat on the Thames in 1837. (See STEAM ENGINE.) The first naval screw vessel, the Archimedes, built for the British navy in 1840, was so perfect- ly successful that comparatively few paddle steamers were subsequently built. The ear- liest regular transatlantic line of steamers, the Cunard line, sent its first vessel, the Britan- nia, of 1,350 tons, from Liverpool, July 4, 1840. In 1847 Capt. R. B. Forbes took out the first transatlantic screw steamer, the Mas- sachusetts, and introduced steam vessels into Chinese waters, sending out hulls and machin- ery from the United States in sailing vessels. Attempts have been made within a few years to revive the system of hydraulic propulsion first tried a century ago by Rumsey. Chain propulsion has in some instances proved very satisfactory. A chain or wire rope is laid in the bed of the river, or along the proposed route of the steamer, and passes over a drum worked by steam engines on the vessel, which is hauled along, taking in the chain at the bow and passing it out astern. In this arrange- ment loss by slip or oblique action is avoided, and a very satisfactory degree of economy is attained. Here, however, but little lateral movement of the vessel is permitted, and only one vessel can make use of the chain. The most successful steam vessels in general use are the screw steamers of transoceanic lines. These are from 350 to 450 ft. long, usually pro- pelled from 12 to 15 knots (14 to 17 m.) an hour, by engines of from 3,000 to 4,000 horse power, consuming from 70 to 100 tons of coal a day, and crossing the Atlantic in from 8 to STEARIO ACID 10 days. These vessels are now invariably fitted with the compound engine and surface condensers. The largest vessel yet constructed is the Great Eastern, fig. 5, begun in 1854 and completed in 1859, by J. Scott Russell, on the Thames, England. This ship is 680 ft. long, FIG. 5. Great Eastern. 83 ft. wide, 58 ft. deep, 28 ft. draught, and of 24,000 tons measurement. There are four pad- dle and four screw engines, the former having steam cylinders 74 in. in diameter with 14 ft. stroke, the latter 84 in. in diameter and 4 ft. stroke. They are collectively of 10,000 actual horse power. The paddle wheels are 56 ft. in diameter, the screw 24 ft. The steam boilers supplying the paddle engines have 44,000 sq. ft. (more than an acre) of heating surface. The boilers supplying the screw engines are still larger. At 30 ft. draught this great vessel dis- places 27,000 tons. The engines were designed to develop 10,000 horse power, driving the ship at the rate of 16 statute miles an hour. STEAUIC ACID (Gr. artap, tallow), a fatty acid obtained from mutton suet, and other fats that contain stearine, by saponifying suet and de- composing the hot solution of the soap with hydrochloric, or still better with tartaric acid. The oily acids are next submitted to pressure between hot plates, by which means a large portion of the oleic acid is separated ; the solid residue is then to be purified by recrystalliza- tion from alcohol three or four times. Its formula is HCi 8 H 3 eOa. When recrystallized from ether, until the fusing point becomes con- stant at 159, and slowly cooled, the acid forms beautiful colorless, transparent, rhombic plates ; these melt into a colorless oil, tasteless and without odor, and when quickly cooled the substance concretes in a white crystalline mass, which is insoluble in water, but readily forms with hot alcohol a solution having acid reac- tion. It is the material of the so-called stear- ine candles. Stearic acid exists in fats in combination with glycerine, forming stearine,
