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the school, which was moved to extensive new buildings at Horsham. The London buildings were subsequently taken down. The school at Horsham is conducted on the ordinary lines of a public school, and can accommodate over 800 boys. It includes a preparatory school for boys, established in 1683 at Hertford, where the buildings have been greatly enlarged for the use of the girls’ school on the same foundation. This was originally in Newgate Street, but was moved to Hertford in 1778. In the boys’ school the two highest classes retain their ancient names of Grecians and Deputy Grecians. Children were formerly admitted to the schools only on presentation. Admission is now (1) by presentation of donation governors (i.e. the royal family, and contributors of £500 or more to the funds), of the council of almoners (which administers the endowments), or of certain of the city companies; (2) by competition, on the nomination of a donation governor (for boys only), or from public elementary schools in London, certain city parishes and certain endowed schools elsewhere. The main school is divided into two parts—the Latin school, corresponding to the classical side in other schools, and the mathematical school or modern side. Large pension charities are administered by the governing body, and part of the income of the hospital (about £60,000 annually) is devoted to apprenticing boys and girls, to leaving exhibitions from the school, &c.

CHRISTY, HENRY (1810–1865), English ethnologist, was born at Kingston-on-Thames on the 26th of July 1810. He entered his father’s firm of hatters, in London, and later became a director of the London Joint-Stock Bank. In 1850 he started on a series of journeys, which interested him in ethnological studies. Encouraged by what he saw at the Great Exhibition of 1851, Christy devoted the rest of his life to perpetual travel and research, making extensive collections illustrating the early history of man, now in the British Museum. He travelled in Norway, Sweden, Denmark, Mexico, British Columbia and other countries; but in 1858 came the opportunity which brought him fame. It was in that year that the discoveries by Boucher de Perthes of flint-implements in France and England were first held to have clearly proved the great antiquity of man. Christy joined the Geological Society, and in company with his friend Edouard Lartet explored the caves in the valley of the Vézère, a tributary of the Dordogne in the south of France. To his task Christy devoted money and time ungrudgingly, and an account of the explorations appeared in Comptes rendus (Feb. 29th, 1864) and Transactions of the Ethnological Society of London (June 21st, 1864). He died, however, on the 4th of May 1865, of inflammation of the lungs supervening on a severe cold contracted during excavation work at La Palisse, leaving a half-finished book, entitled Reliquiae Aquitanicae, being contributions to the Archaeology and Palaeontology of Perigord and the adjacent provinces of Southern France; this was issued in parts and completed at the expense of Christy’s executors, first by Lartet and, after his death in 1870, by Professor Rupert Jones. By his will Christy bequeathed his magnificent archaeological collection to the nation. In 1884 it found a home in the British Museum. Christy took an earnest part in many philanthropic movements of his time, especially identifying himself with the efforts to relieve the sufferers from the Irish famine of 1847.

CHROMATIC (Gr. χρωματικός, coloured, from χρῶμα, colour), a term meaning “coloured,” chiefly used in science, particularly in the expression “chromatic aberration” or “dispersion” (see Aberration). In Greek music χρωματικὴ μουσική was one of three divisions—diatonic, chromatic and enharmonic—of the tetrachord. Like the Latin color, χρῶμα was often used of ornaments and embellishments, and particularly of the modification of the three genera of the tetrachord. The chromatic, being subject to three such modifications, was regarded as particularly “coloured.” To the Greeks chromatic music was sweet and plaintive. From a supposed resemblance to the notes of the chromatic tetrachord, the term is applied to a succession of notes outside the diatonic scale, and marked by accidentals. A “chromatic scale” is thus a series of semi-tones, and is commonly written with sharps in ascending and flats descending. The most correct method is to write such accidentals as do not involve a change of key.

CHROMITE, a member of the spinel group of minerals; an oxide of chromium and ferrous iron, FeCr2O4. It is also known as chromic iron or as chrome-iron-ore, and is the chief commercial source of chromium and its compounds. It crystallizes in regular octahedra, but is usually found as grains or as granular to compact masses. In its iron-black colour with submetallic lustre and absence of cleavage it resembles magnetite (magnetic iron-ore) in appearance, but differs from this in being only slightly if at all magnetic and in the brown colour of its powder. The hardness is 5½; specific gravity 4.5. The theoretical formula FeCr2O4 corresponds with chromic oxide (Cr2O3) 68%, and ferrous oxide 32%; the ferrous oxide is, however, usually partly replaced by magnesia, and the chromic oxide by alumina and ferric oxide, so that there may be a gradual passage to picotite or chromespinel. Much of the material mined as ore does not contain more than 40 to 50% of chromic oxide. In the form of isolated grains the mineral is a characteristic constituent of ultrabasic igneous rocks, namely the peridotites and the serpentines which have resulted from their alteration. It is also found under similar conditions in meteoric stones and irons. Often these rocks enclose large segregated masses of granular chromite. The earliest worked deposits were those in the serpentine of the Bare Hills near Baltimore, Maryland, U.S.A.; it was also formerly extensively mined in Lancaster county, Pennsylvania, and is now mined in California, as well as in Turkey, the Urals, Dun Mountain near Nelson in New Zealand, and Unst in the Shetlands.

Chrome-iron-ore is largely used in the preparation of chromium compounds for use as pigments (chrome-yellow, &c.) and in calico-printing; it is also used in the manufacture of chrome-steel.  (L. J. S.) 

CHROMIUM (symbol Cr. atomic weight 52.1), one of the metallic chemical elements, the name being derived from the fine colour (Gr. χρῶμα) of its compounds. It is a member of the sixth group in the periodic classification of the elements, being included in the natural family of elements containing molybdenum, tungsten and uranium. The element is not found in the free state in nature, nor to any large extent in combination, occurring chiefly as chrome-ironstone, Cr2O3·FeO, and occasionally being found as crocoisite, PbCrO4, chrome-ochre, Cr2O3, and chrome-garnet, CaO·Cr2O3·3SiO2, while it is also the cause of the colour in serpentine, chrome-mica and the emerald. It was first investigated in 1789 by L. N. Vauquelin and Macquart, and in 1797 by Vauquelin, who found that the lead in crocoisite was in combination with an acid, which he recognized as the oxide of a new metal.

The metal can be obtained by various processes. Thus Sainte Claire Deville prepared it as a very hard substance of steel-grey colour, capable of taking a high polish, by strong ignition of chromic oxide and sugar charcoal in a lime crucible. F. Wöhler reduced the sesquioxide by zinc, and obtained a shining green powder of specific gravity 6.81, which tarnished in air and dissolved in hydrochloric acid and warm dilute sulphuric acid, but was unacted upon by concentrated nitric acid. H. Moissan (Comptes rendus, 1893, 116, p. 349; 1894, 119, p. 185) reduces the sesquioxide with carbon, in an electric furnace; the product so obtained (which contains carbon) is then strongly heated with lime, whereby most of the carbon is removed as calcium carbide, and the remainder by heating the purified product in a crucible lined with the double oxide of calcium and chromium. An easier process is that of H. Goldschmidt (Annalen, 1898, 301, p. 19) in which the oxide is reduced by metallic aluminium; and if care is taken to have excess of the sesquioxide of chromium present, the metal is obtained quite free from aluminium. The metal as obtained in this process is lustrous and takes a polish, does not melt in the oxyhydrogen flame, but liquefies in the electric arc, and is not affected by air at ordinary temperatures. Chromium as prepared by the Goldschmidt process is in a passive condition as regards dilute sulphuric acid and dilute hydrochloric acid at ordinary temperatures; but by heating the metal with the acid it passes into the active condition, the same effect being produced by heating the inactive form with a solution of an alkaline halide.