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RADISH

1580

RAFFIA

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 Astrophys-ical 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.

Radium is present in very small quantities in ores containing uranium, the most important being pitch-bl6nd, found in Austria, Sweden and England; carnotite, in Colorado and Utah; autunite, in France, Portugal, etc. The tremendous cost ($120,000 per gram, or 15 grains, of radium element), is due to the long and tedious process necessary to extract the very small amount present in the ore. To produce 2 to 5 centigrams (about J^ to % grains) requires I ton of ore, 5 tons of chemicals and 50 tons of water.

Radium, and other like substances, possess what is known as radio-activity, caused by a spontaneous disintegration of the atoms, somewhat akin to an explosion. This property manifests itself by certain phenonema, as the generation of heat, electricity, the evolution of an active gas, the projection of invisible and penetrating rays, and by light. When a tube containing a radium salt is taken into a dark room it glows with a beautiful soft radiance. Radioactive substances also cause electrified bodies to discharge their electricity; they excite phosphoresence in certain minerals, as willemite, zinc sulphide and the diamond; they act upon photographic plates in a manner similar to ordinary light and the X-rays. Their rays penetrate substances opaque to ordinary light, even passing through a half inch of steel, a foot of solid iron or six inches of lead; and finally, they cause certain changes in the tissues of the body.

The first product of the disintegration of radium is a gas called the "emanation," which in turn, step by step, changes into other elements, called radium A, radium B, etc. This is the transmutation, or conversion of one element into another, hitherto believed impossible. During these changes three kinds of rays are produced, called alpha, beta and gamma. The alpha rays are atoms of helium having charges of positive electricity and are projected with a velocity 1-20 that of light. Their flight can be observed through an instrument called the spinthariscope. The beta rays are atoms of negative electricity or electrons (see ATOM), while the gamma rays are pulsations transmitted through the ether with the velocity of light.

In spite of the fact that a grain of radium bromide expels every second about ten thousand million alpha-particles, it has been estimated that it would take many thousand years before the complete disappearance of the salt.

Many extravagant claims have been made that in radium has been found a cure for cancer. These claims I have carefully considered and with Dr. William Seaman Bain-bridge, Surgeon to the Hospital, I have spent much time at the medical centers abroad that are testing radium. My conclusions are, that while of great benefit in certain forms of cancer, there is but one universally recognized cure—the early use of the knife. It will take years of careful study to determine the true value of radium in the treatment of cancer. It has proved beneficial in the treatment of superficial cancer, lupus, keloid and kindred conditions.

WORTHINGTON SEATON R0SSELL   M. D.

Research Fellow and Chief X-Ray Department, New York Skin and Cancer Hospital.

Rae (ra), 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 ne 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.