692 THE POPULAR SCIENCE MONTHLY. 



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 ob- 

 tained 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 vari- 

 ous 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 co- 

 operative, 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 lect- 

 ures 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 ap- 

 pointment in 1884. Here he organized and equipped a physical 

 laboratory in connection with the office of the Chief Signal Officer, 



