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* PULKOVA OBSEEVATOEY. 537 PULMONATA. migue central de Poulkova (Saint Petersburg, 1845); Publications de I'observatoire central Xicolas (Saint Petersburg, 1893-1901). PUL'LAN, RicHABD Popple WELL (1825-88). An English architect and archseologist, born in Knaresborough, Yorkshire, and educated at Christ's Hospital. He studied architecture under Richard Lane in Manchester, early devoted him- self to polychromy, and with Wyatt had charge of the decoration of the Byzantine and Gothic halls of the Crystal Palace (1851). In 1857 he was sent by the architectural department of the Foreign Office to examine the Halicarnassus mausoleum and to make excavations in Cnidus (q.v.) ; this work is described in A History of the Discoveries at Halicarnassus, etc. (London, 1802-03). Pullan was employed in 1802 in excavating the Temple of Bacchus at Teos. and that of Apollo Smintheus in the Troad; and in 1869 on the Temple of Athene Polias at Priene. He built several churches in Italy, and wrote Byzantine Architecture (1864), Principal Ruins of Asia Minor (1865), Eastern Cities and Italian Toic-ns (1879), and Lectures on Christian Architecture (1879). PULLET. One of the many provincial names for the British edible clam (Mya truncuta). See Clam, and accompanying Colored Plate. PULLET, Aunt. A leading character in George Eliot's Hill on the Floss, the sister of Mrs. Tulliver, a selfish invalid, who domineers over her husband. PULLEY (OP., Fr. poulie, probably from LGer. pulen, AS. pullian, Eng. pull). A circu- lar wheel turning on a smooth axle through its centre, and with a grooved cut in its rim so that a cord can run around it. A 'fixed' pulley is one whose axle is fixed to some support ; while a free pulley is not stationary, but is carried in the bight of the cord passing over it. A fixed pulley simply changes the direction of the force Fig. 1. Fig. i. which the cord exerts. If in Fig. 1 Fj and Fj are two forces acting on a cord passing over a pulley, they will be equal if the system is in equilibrium. If a free pulley carrying a weight is supported by a cord, as shown in Fig. 2, there are three forces acting on the pulley, a force F„ vertically down equal to the weight of the pulley and the weight it carries, and two forces obliquely up- ward each equal to Pj due to the two branches of the cord which passes over the pulley. If the branches of the cord make an angle 6 with the vertical, 2FiCos9 is the total force acting verti- cally upward; 2F,Jose = Fj; r? is 2eos9. therefore if there is equilibrium and the mechanical advantage. In particular, if, as is usually the case, the two branches of the cord are parallel and vertical, e = 0, and 2F, = F.. This same fornuila may be deduced by consider- ing the system displaced slightly from equilib- rium, using the principle of the "conservation of energy. Fixed and free pulleys may be combined in many ways, but the principle is evident. If a continuous cord passes over a free compound pulley — made up of several independent wheels — in such a manner that there are » supporting branches of the cord, the mechanical advantage is n. Pulleys are also made in which two toothed wheels of different radii are clamped together, so that as one turns the other must also ; and the cord is replaced by a chain whose links fit into the teeth. Such a pulley is called a 'differ- ential' one. If one wheel has in its rim N teeth, and the other X — 1, the mechanical ad- vantage is 2N. The principle of the action of pulleys was first given by Stevinus. See Block; Tackle. PULL'MAN. An industrial toTi now form- ing a part of the southernmost ward of Chicago. It was founded in 1880 by George M. Pullman, wlio established here the extensive shops of the Pullman Palace Car Company. The town was laid out along artistic and scientific lines, with handsome brick houses, wide streets, flower gar- dens, a fine school building, library, hotel, and theatre, and was under the sole control of the company. The idea of the promoter was to secure for his employees all the advantages which might accrue from congenial surroundings. The high rates charged for rent, water, and gas. how- ever, caused dissatisfaction among the residents, and in 1889 they voted in favor of annexation to Chicago. Population, at that time, about 12,- 000. Consult Doty, The Town of Pullman (Pull- num, 1S!I3). PULLMAN, George Mortimer (1831-97). An American inventor, born in Chautauqua Count}-, X. Y. He worked for a time as a cabinet- maker with an elder brother in Albion, X. Y., .Tnd in 1853 took a contract for moving buildings that obstructed the idpning of the Erie Canal. Six years later he removed to Chicago, where he did business as a building contractor. In the same year that he reached Chicago he remodeled two old coaches into sleeping cars. Four years later he built the first new sleeping ear, 'Pioneer.' upon lines of the now famous •Pullman' cars. In 1807 he organized the Pullman Palace Car Com- pany, and was its president until his death. In 1880 he founded for his employees the model town of Pullman (q.v.) and attempted to make the place an ideal home for his men. In 1887 he invented and put into execution the idea of vesti- bule trains. He was also connected with various other industrial undertakings, and was president of the company which put into operation the Manhattan Elevated Railroad of New York City. PULMONATA (Xeo-Lat. nom. pi., from Lat. piihno. lung). An order of air-breathing gastro- pod mollusks having no gills, but the mantle- cavity modified into a respiratory sac or 'lung,*