American astronomer born on December 20, 1876 in Antioch (Syria) and died on May 11, 1956 in Pasadena, California. Son of an American missionary couple, met for the first time their country eight years of age. He/She studied astronomy at Dartmouth College in Hanover (New Hampshire) and the universities of Chicago and Munich. In his research he/she used the spectroscope to observe sunspots, measured the rotation of this star, whose speed depends on latitude, and carried out calculations of speeds and distances of hundreds of stars. He/She was its director since 1924 member of the body of researchers at Mount Wilson Observatory, and between 1923 and 1946. One of its measures, relating to the white dwarf companion of Sirius, was one of the first empirical confirmations of the theory of relativity. Projects that addressed during his time as director of the Observatory, include construction of 5,080 mm mount Palomar Telescope.