MICHELSON, ifrkel-SOIL ALBERT AnRAtiAir I 1852-1. An American physicist, born in Strelno, Germany, and brought up in San Fran cisco. Ile graduated from the Naval Academy in 1873, and after several years' service in the navy went abroad and studied at Berlin, Heidel berg. and Paris (1880-S2). On his return to America, Michelson became professor of phys ics at the Case School of Applied Science, Cleveland, Ohio ; t hen held a like chair in Clark University (1889-921; and in 1892 became head of the department of physics in the University of Chicago. Professor son's achievements in optics secured for him an international reputation. His determinations of the velocity of light are of the greatest impor tance, and his results are marked by a high de gree of accuracy. These experiments were begun in 1878. when Professor Michelson was at the Naval Academy, and were in 1882. Ilis invention, in 1887, of an interferential refrac tometer enabled him to determine linear distances in terms of the wave length of light. and he
Was invited by the International Bureau of Weights and Measures at Paris to ascertain the length of the standard meter in terms of the wave length of cadmium light. This investiga tion was of great. importance in that it enables the Meter of the Archives to be reproduced at any time by reference to certain known quantities which are not only constant, but also are readily reproducible. In connection with Professor Mor ley. Professor Michelson carried on a series of -elaborate experiments designed to show the rela tive motion of platter and ether. He also devised the echelon spectroscope, by which he was able to secure greater dispersion than with a prism, and thus was able to study the Zeeman effect and other phenomenh. He was elected a member of the National Academy of Sciences and of the International Committee on Weights and Meas ures, a fellow of the Royal Astronomical Society, and of other learned bodies.