RADISH

1580

RAG-STONE

of a thermoelectric couple suspended between the poles of a strong permanent magnet. The thermoelectric couple is a part of a short electric circuit, all of which is freely suspended. When one junction in this circuit is exposed to radiation, an electric current is produced and the suspended coil rotates exactly as does the coil in an ordinary D'Arsonval galvanometer. (See Galvanometer.) To the suspended coil is attached a mirror by which this rotation may be measured. The instrument in its present form was suggested by D'Arsonval and perfected by C. V. Boys, in whose hands it has been made so sensitive as to detect the radiation of a single candle two miles away. For its use as an instrument of precision see article by E. P. Lewis in Astrophysical Journal, June, 1895, pp. 1-25.

Rad'ish, a name applied to species of Raphanus, a genus of the mustard family, and especially to R. sativus, long cultivated, principally for its fleshy roots. It is native to the Old World and many garden varieties have been developed, which may be classed in general as long-rooted and turnip-rooted varieties.

Ra'dium is an elementary metallic substance, so called because it emits rays which render luminous sensitive objects on which they are thrown. It was discovered by Professor Pierre Curie of Paris University and Madame Sklodowska Curie, his wife. It is exceedingly scarce and possesses extraordinary physical properties. It is found in the refuse of uranium ore, and is separated by a long series of crystallizations, eight tons of residues yielding only 15 grains of radium chloride. Only a few ounces of radium have been obtained up to the present time, and its value is about three thousand times its weight in gold. It has been asserted that to produce one kilo would cost $,ooo,ooo. It looks like common salt, with a yellowish tint. It gives off light and heat constantly, and with a diminution of the substance so slight that it cannot be measured by the most delicate instruments. It maintains its own temperature 1.50 C. above its surroundings, and it has been claimed that its light can penetrate three feet of iroar-It emits invisible rays which affect a photographic sensitive plate, and have a powerful effect on animal life. Proximity of radium to the human skin produces dangerous sloughing sores, and death from paralysis may follow. Blindness is a frequent result. On the other hand, experiments indicate that radium may be used successfully in the treatment of cancer, lupus and kindred diseases. It has also been shown that development of animal organisms may be arrested, and life may be prolonged far beyond its natural limit, by exposure to the influence of radium.

Radium in the metallic or pure state has not yet been isolated, but is known only in combination with chlorine, as chloride, with bromine, as bromide, or with the radical of nitric acid, as nitrate. Radium has thus far been found chiefly in Bohemia. In America Professor Magie has discovered and extracted radium from carnolite, a mineral which is abundant in Utah. At Llano, Texas, quantities of earth have been found in which the presence of radium is indicated.

Rae (r), John, Arctic traveler, was born near Stromnes on the Orkney Islands, north of Scotland, in 1813, and, after studying medicine at Edinburgh, went to Hudson Bay as physician of the company's ships. In 1845 he undertook an exploring expedition and in 1846-7 a more extensive one, wintering in Repulse Bay. He was second in command on a search-voyage for Franklin in 1848, and five years later commanded an expedition that proved King William's Land to be an island. In his journeys he traveled more than 1,800 miles over regions never before explored. He died at London, July 24, 1893.

Raffia is a strong, supple fiber, obtained from the jupati palm, native of South America, and from allied palms in India and Africa. Raffia is extensively used in nurseries and gardens for binding plants and young trees to stakes, that they may grow erect and produce better fruit by greater sunlight being thus afforded. Raffia is also used extensively for mats and even for clothing. Its fiber, though coarse, is very strong and durable.

Rag'lan, Lord (Fitzroy James Henry Somerset), a British general, was born Sept. 30, 1788. He entered the army in his sixteenth year, and after serving on the staff of Sir Arthur Wellesley (afterwards Duke of Wellington) in the Copenhagen Expedition and the Peninsular War became his secretary in 1812. He was made a K. C. B. for brilliant service in the campaign of Waterloo. In September, 1852, he was made master-general of the Ordnance, and a month later was called to the house of peers as Baron Raglan. When war was declared againsi Russia in 1854, Raglan was appointed commander of the TSnglish forces in the Crimea, and at the desperate battle of Inkerman he won the baton of a field-marshal. The siege of Sebastopol continued until June 18, 1855, when a general assault was ordered, at which both English and French troops suffered terrible losses. Raglan had a slight attack of cholera, and this disaster weighed so heavily on his mind that he died a few days later, June 28, 1855. See Kinglake's Invasion of the Crimea.

Rag-Stone, an impure limestone, consisting chiefly of lime and silica, much used for whetstones and building-material.