MENDENHALL, Thomas Corwin, physicist, born near Hanoverton, Ohio, 4 October, 1841. He received a common-school education, but, having a fondness for the study of mathematics and natural science from his childhood, acquired by himself a knowledge of those branches of physics, in which he has since attained note. He was first professor of physics and mechanics in Ohio university in 1873-'8, and then went to Japan as professor of physics in the Imperial university in Tokio. In connection with this appointment he organized the special course of physics and also the physical laboratory of the science department of the university. He founded a meteorological observatory in which systematic observations were made during his residence in Japan, and afterward until it was merged into the general meteorological system that has since been established by the imperial government. From measurements of the force of gravity at the sea-level and at the summit of the extinct volcano Fujiyama, Professor Mendenhall deduced a value for the mass of the earth that agrees closely with that which Francis Baily obtained in England by another method. He also made a series of elaborate measurements of the wave-lengths of the principal Frauenhofer lines of the solar spectrum by means of a large spectrometer, which at the time of its construction was one of the most perfect in existence. He became interested in earthquake phenomena while in Japan, and was one of the founders of the Seismological society of Tokio. In 1881 he returned to the United States and resumed his chair at Ohio state university. He organized the Ohio state weather service in 1882, was its director until 1884, and was the first to devise and put into operation a system of weather-signals for display on railroad-trains. This method became general throughout the United States and Canada, and continued to be employed until the introduction in 1887 of a new code by the chief signal officer. In i884 he became professor in the United States signal service, and was charged with the or canization and equipment of a physical laboratory in connection with the bureau in Washington, with the introduction of systematic observations of atmospheric electricity, and with the investigation of methods for determining ground-temperatures. He was the first to establish stations in the United States for the systematic observation of earthquake phenomena. Immediately after the Charleston earthquake, on 31 August, 1886, he visited that city and made a report upon the agitation, with a co-seismic chart of the disturbed area. In 1886 he resigned from the government service to accept the presidency of Rose polytechnic institute. Terre Haute, Indiana Professor Mendenhall has lectured extensively throughout the United States on subjects that relate to physics, and in Japan he was one of the American professors that in addition to their university duties gave public lectures on scientific subjects to general audiences in the temples and theatres of the city of Tokio, resulting in the establishment of the first public lecture hall in the empire. He received the degree of Ph.D. from Ohio university in 1878, and that of LL.D. from the University of Michigan in 1887. Besides membership in other scientific societies, Professor Mendenhall in 1882 was vice-president for the physical section of the American association for the advancement of science, and in 1887 was elected to the National academy of sciences. In addition to papers, scientific monographs, and special reports, he has published "A Century of Electricity" (Boston, 1887).