inferior to that of Sir W. Rowan Hamilton. But his thirst for knowledge was unlimited in its range. He was not content with languages, mathematics, and physical science: natural science, medicine, and even ancient philosophy were eagerly studied by him; and he was passionately devoted to athletic exercises. His medical studies were pursued successively in London, Edinburgh, Gottingen, and finally at Emmanuel College, Cambridge, where he took his doctor's degree. The death of a maternal uncle put him in a position of comfortable independence, and he did not heartily enter upon practice. He was secured in 1802 by the Royal Institution as a colleague of Davy and professor of natural philosophy. Here his special talents found ample occupation, and the chief result was the publication in 1807 of his celebrated Course of Lectures on Natural Philosophy, a work which is even now regarded as a valuable authority. Some years before he had made his remarkable discovery of the interference of light, and begun that wonderful series of researches which, as completed by Fresnel, secured the triumph of the undulatory theory. He was foreign secretary of the Royal Society for more than a quarter of a century; and it is curious to note that his reputation stood higher in foreign than in home scientific circles. He was one of the eight foreign associates of the Institute of France. He was one of the Commission ers of Weights and Measures, and secretary to the Board of Longitude, which in those days conducted the Nautical Almanac. A few years before his death he became inter ested in life assurance, with great benefit to the company whose scientific business he conducted. His death, on 10th May 1829, was probably hastened by the extraordinary amount and variety of the labours he undertook, and the self-sacrificing zeal with which he devoted himself to them.
His Life, by Dr Peacock, dean of Ely and a well-known mathematician, was published in 1855, along with a collection of his Miscellaneous Works and Scientific Memoirs. Young was a somewhat copious contributor to the 6th edition of this Encyclopedia, and some of the best of his smaller papers appeared in it for the first time. For a resume of his contributions to the subject of haemadynamics, see Vascular System, p. 97 supra. Another of the multitudinous problems that claimed his attention was the decipherment of the Egyptian hieroglyphics, in which he had made some progress as early as 1814; see his Account of some Recent Discoveries in Hieroglyphical Literature (London, 1823).
YOUNGSTOWN, a city and the county seat of Mahoning county, Ohio, United States, is situated upon the Mahoning river, a tributary of the Ohio. The prevailing industries of the surrounding country are agriculture and coal-mining. Youngstown is directly connected with six railway lines. Owing to the contour of the site, the city is laid out very irregularly. The population in 1880 was 15,435 (8075 in 1870). The industries of Youngstown are connected chiefly with the manufacture of iron: there are several furnaces and rolling-mills, and manufactories of rails and stoves and of agricultural tools and machines.
Youngstown was laid out in 1797, being one of the first settlements made in that part of Ohio known as the Western Reserve. Since the rebellion it has grown with great rapidity.
YPRES (Flem. Yperen a town of Belgium, capital of an arrondissement in the province of West Flanders, stands in a fertile plain on the Yperlee, 21 miles north-north-west of Lille. In the 14th century it is said to have contained 200,000 inhabitants; and it was long famous for its woollen and linen manufactures, though the once current derivation of the word " diaper " from the name of this town can no longer be maintained. Of the old fortifications some traces still remain, as well as a few picturesque dwelling-houses of the 14th and 15th centuries. The fine Gothic cloth hall (1201-1342), with a facade 462 feet in length, is pierced by two rows of pointed windows; there are two corner turrets; and in the centre rises a massive square clock tower. The forty-four statues of counts of Flanders and their consorts which formerly adorned it were restored in 1860. The town-hall (1730) contains some interesting frescos and sculptures of modern date. The finest parts of the Gothic cathedral of St Martin (1221-70) are the choir, and the portal and rose window of the south transept; in the interior is some good woodcarving; the old frescos were " restored " in 1826. In the cloister is the tomb of Cornelius JANSEN (q.v.). The town contains several other churches, as well as hospitals, a military school, a museum, and a public library. The chief manufactures are those of linen thread and lace and of woollen and linen cloth; dyeing, bleaching, and tanning are also carried on. The population in 1876 was 15,515.
YRIARTE. See Iriarte.
YTTRIUM, the name of a rare element which in its character is closely allied to, and in nature is always associ ated with, cerium, lanthanum, didymium, and erbium (see LANTHANUM, vol. xiv. p. 291). For the preparation of yttrium compounds the best raw material is a rare Swedish mineral called gadolinite, which, according to Konig, consists of 22 61 per cent, of silica, 34 64 of yttria, Y 2 O 3, and 42 75 of the oxides of erbium, cerium, didymium, lanthanum, iron, beryllium, calcium, magnesium, and sodium. Bunsen and Bahr, in 1866, elaborated a method for extracting the several rare oxides in the state of purity; but the method is too complicated to reproduce here.[1] Metallic yttrium is obtainable by reducing the chloride with potassium; but this operation has never been carried out with pure chloride. Yttria, Y 2 3, is a yellowish white powder, which at high temperatures radiates out a most brilliant white light. It is soluble, slowly but completely, in mineral acids. It is recognized most surely by its very characteristic spark spectrum. Solutions of yttria salts in their behaviour to reagents are not unlike those of zirconia. The atomic weight of yttrium, according to the latest researches,[2] is 89·02, if O = 16.
Boundaries, area, &c.
YUCATAN, a peninsular region of Central America, Boundforming the south-eastern extremity of Mexico (see vol. aries > xvi. pi. I.), of which, since 1861, it constitutes the two area> confederate states of Campeche (Campeachy) in the west and Yucatan in the east. At its neck the peninsula is conterminous on the south-east with British Honduras, on the south-west with the state of Tabasco (Mexico), and on the south with the republic of Guatemala, the boundaries towards these territories being largely of a purely conventional character. From this base the land projects in a compact rectangular mass between the Gulf of Mexico and the Caribbean Sea, west and east, for 280 miles northwards, across nearly four degrees of latitude (18 to 21 40 N.) and three of longitude (87 30 to 90 30 W.), to within 120 miles of Cuba, from which it is separated by the Yucatan Channel. It has a mean breadth of about 200 miles, a coast-line of 700 miles, and a total area of 55,400 square miles, with a population in 1882 of 393,000 (Yucatan, 29,570 square miles, population 302,500; Campeche, 25,830 square miles, population 90, 500).[3]
Physical features.The coast-line presents a uniform monotonous aspect, being fringed by no islands except Cozumel near the northeast point, and broken by no indentations except the shallow Lake Terminos on the west and the inlets of Ascension, Espiritu Santo, and Chetumal Bays on the east side. But the north coast is skirted by an almost continuous line of low dunes, nearly 200 miles long, enclosing a broad lagoon, which varies in length and depth with the
