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Rh Alexander, accompanied by his brother Nicholas and a remnant of his followers, retreated to Rimnik, where he spent some days in negotiating with the Austrian authorities for permission to cross the frontier. Fearing that his followers might surrender him to the Turks, he gave out that Austria had declared war on Turkey, caused a Te Deum to be sung in the church of Rosia, and, on pretext of arranging measures with the Austrian commander-in-chief, crossed the frontier. But the Austria of Francis I. and Metternich was no asylum for leaders of revolts in neighbouring countries. Ypsilanti was kept in close confinement for seven years, and when released at the instance of the emperor Nicholas I. of Russia, retired to Vienna, where he died in extreme poverty and misery on the 31st of January 1828.

(1793–1832), second son of Prince Constantine, distinguished himself as a Russian officer in the campaign of 1814, and in the spring of 1821 went to the Morea, where the war of Greek independence had just broken out. He was one of the most conspicuous of the Phanariot leaders during the earlier stages of the revolt, though he was much hampered by the local chiefs and by the civilian element headed by Mavrocordato. In January 1822 he was elected president of the legislative assembly; but the ill-success of his campaign in central Greece, and his failure to obtain a commanding position in the national convention of Astros, led to his retirement early in 1823. In 1828 he was appointed by Capo d’Istria commander of the troops in East Hellas. He succeeded, on the 25th of September 1829, in forcing the Turkish commander Aslan Bey to sign a capitulation at the Pass of Petra, which ended the active operations of the war. He died at Vienna on the 3rd of January 1832.

Gregory Ypsilanti (d. 1835), third son of Prince Constantine, founded a princely family still settled near Brünn. Nicholas Ypsilanti wrote Mémoires valuable as giving material for the antecedents of the insurrection of 1820 and the part taken in them by Alexander I. of Russia. They were published at Athens in 1901.

See the works cited in the bibliography of the article , especially the  of J. Philemon.  YPSILANTI, a city of Washtenaw county, Michigan, U.S.A., on the Huron river, 30 m. W. by S. of Detroit. Pop. (1900) 7378; (1904) 7587; (1910) 6230. It is served by the Michigan Central and the Lake Shore & Michigan Southern railways, and is the seat of the Michigan State Normal College (1849). There are various manufactures. Ypsilanti was laid out and named in honour of Demetrius Ypsilanti, the Greek patriot, in 1825; it was incorporated as a village in 1832, and chartered as a city in 1858.  YSAŸE, EUGÈNE (1858–), Belgian violinist, was born at Liége, where he studied with his father and under R. Massart, at the Conservatoire, until he was fifteen; he had some lessons from Wieniawski, and later from Vieuxtemps. In 1879 Ysaÿe played in Germany, and next year acted as leader of Bilse's orchestra in Berlin; he appeared in Paris in 1883, and for the first time in London at a Philharmonic concert in 1889. He was violin professor at the Brussels Conservatoire from 1886 to 1898, and instituted the celebrated orchestral concerts of which he was manager and conductor. Ysaÿe first appeared as conductor before a London audience in 1900, and in 1907 conducted Fidelio at Covent Garden. The sonata concerts in which he played with Raoul Pugno (b. 1S52), the French pianist, became very popular in Paris and Brussels, and were notable features of several London concert seasons. As a violinist he ranks with the finest masters of the instrument, with extraordinary temperamental power as an interpreter. His compositions include a Programme Symphony (played in London, 1905), a Piano Concerto, and a “Suite Wallonne.”  YSTAD, a seaport of Sweden on the S. Baltic coast, in the district (län) of Malmöhus, 39 m. E.S.E. of Malmö by rail. Pop. (1900) 9862. Two of its churches date from the 13th century. Its artificial harbour, which admits vessels drawing 19 ft., is freer from ice in winter than any other Swedish Baltic port. Apart from a growing import trade in coal and machinery,

its commerce has declined; but it is among the first twelve manufacturing places in Sweden, having large mechanical workshops.  YTTERBIUM [symbol, Yb; atomic weight, 172.0 (O = 16)], a metallic chemical element belonging to the rare earth group. Mixed with scandium it was discovered by Marignac in gadolinite in 1878 (see ). The oxide, Yb2O3, is white and forms colourless salts; the crystallized chloride, YbCl3·6H2O, forms colourless, deliquescent crystals; the anhydrous chloride sublimes on heating (C. Matignon, Ann. chim. phys., 1906 (8), 8, p. 440). In 1907 G. Urbain separated ytterbium into two new elements, neo-ytterbium and lutecium (atomic weight, 174.0); and in 1908 C. A. von Welsbach published the same result, naming his elements aldebaranium and cassiopeium (on the question of priority see F. Wenzel, Zeit. anorg. Chem., 1909, 64, p. 119).  YTTRIUM [symbol, Y; atomic weight, 89.0 (O = 16)], a metallic chemical clement. In its character yttrium is closely allied to, and in nature is always associated with, cerium, lanthanum, didymium and erbium (see ). For the preparation of yttrium compounds the best raw material is gadolinite, which, according to König, consists of 22.61% of silica, 34.64 of yttria, Y2O3, and 42.75 of the oxides of erbium, cerium, didymium, lanthanum, iron, beryllium, calcium, magnesium and sodium. The extraction (as is the case with all the rare earths) is a matter of great difficulty. Metallic yttrium is obtainable as a dark grey powder by reducing the chloride with potassium, or by electrolysing the double chloride of yttrium and sodium. It decomposes water slowly in the cold, and more rapidly on heating. Yttria, Y2O3, is a yellowish white powder, which at high temperatures radiates out a most brilliant while light. It is soluble, slowly but completely, in mineral acids. It is recognized by its very characteristic spark spectrum. Solutions of yttria salts in their behaviour to reagents are not unlike those of zirconia. The atomic weight was determined by Cleve.  YUCATAN, a peninsula of Central America forming the S.E. extremity of the republic of Mexico and including the states of Campeche and Yucatan and the territory of Quintana Roo. Small parts of British Honduras and Guatemala are also included in it. The natural boundary of the peninsula on the S. is formed in part by the ridges extending across N. Guatemala, the line terminating E. at the lower part of Chetumal Bay, and W. at Laguna de Terminos. From this base the land extends N. between the Gulf of Mexico and Caribbean Sea in nearly rectangular form for about 280 m., with about the same extreme width in longitude. It has a mean breadth of about 200 m., a coast-line of 700 m. and an area of about 55,400 sq.m.

The coast on the N. and W. is low, sandy and semi-barren, and is made dangerous by the Campeche banks, a northward extension of the peninsula, covered with shifting sands. The outer shore-line on the N. for nearly 200 m. consists of a narrow strip of low sand dunes, within which is a broad channel terminating to the E. in a large lagoon. There are a number of openings through the outer bank and several small towns or ports have been built upon it. The E. coast consists of bluffs, indented with bays and bordered by several islands, the larger ones being Cozumel (where Cortés first landed), Cancum, Mujeres and Contoy. There is more vegetation on this coast, and the bays of Chetumal, Espiritu Santo, Ascencion and San Miguel (on Cozumel Island) afford good protection for shipping. It is, however, sparsely settled and has little commerce.

The peninsula is almost wholly composed of a bed of coralline and porous limestone rocks, forming a low tableland, which rises gradually toward the S. until it is merged in the great Central American plateau. It is covered with a layer of thin, dry soil, through the slow weathering of the coral rocks. The surface is not so level and monotonous as it appears on many maps; for, although there are scarcely any running streams, it is diversified by a few lakes, of which Bacalar and Chichankanab are the largest, as well as by low isolated hills and ridges in the W., and in the E. by the Sierra Alta, a range of moderate elevation traversing the whole peninsula from Catoche Point S. to the neighbourhood of Lake Peteu in Guatemala. The culminating points of the W. ridges do not exceed 900 ft., and some authorities estimate it at 500 ft. 