the founders of the Seismological Society of Japan (SSJ). During his time in Japan, he also gave public lectures on various scientific topics to general audiences in temples and in theaters. Returning to Ohio in 1881, Mendenhall was instrumental in developing the Ohio State Meteorological Service. He devised a system of weather signals for display on railroad trains. This method became general throughout the United States and Canada. He became professor at the U.S. Signal Corps in 1884, introducing of systematic observations of lightning, and investigating methods for determining ground temperatures. He was the first to establish stations in the United States for the systematic observation of earthquake phenomena. Resigning in 1886, Mendenhall took up the presidency of the Rose Polytechnic Institute in Terre Haute, Indiana before becoming superintendent of the U.S. Coast and Geodetic Survey in 1889. During his time as superintendent, he issued the Mendenhall Order and oversaw the consequent transition of the United States's weights and measures from the customary system, based on that of England, to the metric system. Mendenhall remained a strong proponent for the official adoption of the metric system all his life. Also, as superintendent of the U.S. Coast and Geodetic Survey, he was also responsible for defining the exact national boundary between Alaska and Canada. The Mendenhall Valley and Glacier in Juneau, Alaska was named for him in 1892. Mendenhall invented the portable Mendenhall Gravimeter in 1890 while he was superintendent of the U.S. Coast and Geodetic Survey, and at that time it provided the most accurate relative measurements of the local gravitational field of the Earth. The gravimeters were used at over 340 survey stations across the US and around the world including Germany, the Netherlands, Java, Philippines, Cuba, Haiti, Bahamas, Dominican Republic, Panama, Canada, and Mexico. The swing of the pendulum was more regular than the most accurate clocks of the era, and as the "world's best clock" it was used by Albert A. Michelson to measure the speed of light, for which he won a Nobel Prize in 1907. An early model of the original 1890s Mendenhall Gravimeter is on display at the Smithsonian Institution in Washington, D.C. Mendenhall was appointed president of the Worcester Polytechnic Institute from 1894 until 1901, when he emigrated to Europe. He returned to the United States in 1912. He was appointed to the board of trustees of the Ohio State University in 1919