Page:Popular Science Monthly Volume 37.djvu/710

692 special course in physics, and established a physical laboratory in connection with the science department of the university. In addition he founded a meteorological observatory, which after his departure was merged into the general meteorological system established by the Japanese Government. Prof. Mendenhall furthermore carried out an investigation on the force of gravity at the sea-level and on the famous Japanese extinct volcano Fujinoyama. His measurements of the figure of the mountain and of its density enabled him to deduce a value for the mass of the earth which agrees very closely with that of Francis Baily as obtained by the Cavendish method. About this time he also made a series of elaborate measurements of the wave-lengths of the principal Fraunhofer lines of the solar spectrum by means of a large spectrometer, then one of the best in existence. This work was done before Prof. Plenry A. Rowland had produced his famous diffraction gratings, but some fine specimens of Lewis M. Rutherfurd's rulings were used. No precise measurements of these rulings were undertaken; hence Prof. Mendenhall's results were only valuable as ascertaining the relative spaces of the various portions of the spectrum; as such they rank among the best given to the world previous to the recent researches with gratings of accurately known and more minute division.

Japan is a land of frequent earthquakes, and Prof. Mendenhall soon became interested in studying their phenomena. That this study on his part and that of others might be systematic and cooperative, he aided in founding the Seismological Society of Tokio. While ardent in his university work and an unsparing toiler in diverse fields of original investigation, Prof. Mendenhall felt that he had a duty to men and women who could not enter his classes nor read the scientific memoirs he was writing. With Prof. Edward S. Morse, then in Japan, and others, he gave lectures on scientific themes to popular audiences in the temples and theatres of Tokio. So thoroughly was an intelligent curiosity thus aroused in the city, that soon a public lecture hall was estab* lished—the first in the Japanese Empire.

In 1881 Prof. Mendenhall returned to the United States and resumed his chair at the Ohio State University. In the following year he organized the Ohio State Weather Service, of which he was director until 1884. While holding this office he devised and put into operation a system of weather-signals for display upon railway trains. This system was generally adopted throughout the United States and Canada; in 1887 it was superseded by a new code introduced by the Chief Signal Officer. In the United States Signal Service at Washington Prof. Mendenhall received an appointment in 1884. Here he organized and equipped a physical laboratory in connection with the office of the Chief Signal Officer,