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ROENTGEN

1624

ROGERS

i. They take their origin at those points where cathode rays strike upon matter. Thus, in the accompanying figure the cone of rays leaving the curved cathode K are

ROENTGEN-RAY TUBE

cathode rays, while the sheaf of rays, S, leaving the flat plate are X-rays. "2. Unlike _cathode rays, they pass through glass, air and various materials with little absorption, 3. Unlike ordinary light, they are _ not reflected or refracted, but pass straight through ordinary material without deviation. 4. They excite fluorescence in many substances, especially in platinum-barium-cyanide and some similar salts. Hence a plate covered with these salts is widely used for observing shadows cast by X-rays. In this manner the bones of the hands, arms or legs, are easily "seen." Such a device is called a fluoroscope. 5. They are not deflected by a magnet as are cathode rays. 6. They produce electrolysis in air and other gases through which they pass. Such gases are made conductors by the passage of X-rays, and are said to be ironized or roentgenized. They behave in a similar way toward parafBne and some other solid insulators. See BECQUEREL RAYS and CATHODE RAYS.

Roentgen (rent'gen), Wiihelm Konrad, eminent German scientist, distinguished investigator of physical problems and discoverer of the X or Roentgen rays, was born in Dtis-seldorf, Prussia, in 1844. Educated at Zurich and Utrecht, he became professor of physics and director of the laboratory at the University of Wiirz-burg, Bavaria. He also taught at Strassburg and at Giessen. In December, 1895, he

communicated to the Wurzburg Physico-Medical Society his remarkable discovery of the new and powerful X-rays, since known by his name, and in the following month he described his discovery at the celebration of the semicentennial of the founding of the Berlin Physical Society. Later he demonstrated the rays in the presence of the Emperor of Germany, who decorated him, and Prince Ludwig of Bavaria created him a baron. The application of the X-rays in surgery has been fraught with wonderful and beneficent results. By the X-ray picture pulmonary tuberculosis is better detected, and heart-disease can be more accurately learned from it than by percussion of the chest.

Rog'ers, Henry Wade, LL.D., American educator and legal authority, was born at Holland Patent, N. Y., Oct. 10, 1853, and educated at the University of Michigan, Ann Arbor. He studied law and in 1877 was admitted to the bar. Later he became professor of law and dean of the law-faculty in his alma mater. In 1890 he was appointed president of Northwestern University, resigning in 1900 and in 1901 accepting the chair of constitutional law at Yale. He is the author of Expert Testimony and Illinois Citations, and for some years edited The American Law Register.

Rogers, John, American sculptor and modeler, was born at Salem, Mass., Oct. 30, 1829, and was educated at the public schools of Boston. Early in life he became interested in • clay-modeling, and in 1858 went to study art in Europe. Returning to the United States in 1859, he modeled a group, The Checker-Players, which attracted favorable attention; after this he took scenes occurring in the Civil War as themes of his compositions; these were soon known as Rogers' Groups and well merited their popularity. The best known, some of which were reproduced in terra-cotta, are the Picket Guard and One More Shot, besides those of a social character, as The Favorite Scholar, Coming to the Parson, Going for the Cows and The Slave-Auction. He also produced a large equestrian statue of General Reynolds, which fronts the city-hall of Philadelphia. He died in July of 1904.

Rogers, Randolph, American sculptor, was born at Waterloo, N. Y., July 6, 1825, and, after following mercantile pursuits in early life, went to Rome to study the sculptor's art. Among his works are the designs for the Washington monument at Richmond, Va., a statue of John Adams in Mt. Auburn cemetery, a memorial monument at Providence, Rhode Island, a still larger one for Michigan at Detroit and the bronze statue of Lincoln at Philadelphia. He died at Rome, Jan. 15, 1892.

Rogers, Samuel, English poet was born at Stoke-Newington, July 30, 1763. After obtaining a private education, he entered

PROFESSOR ROENTGEN