Clemence (1908-1974). Astronomer (Research on motions of planets; introduced measurement of time by means of orbital motions of moon and erth; defined second as fraction of year instead of day). Astronomer, U. S. Naval Observatory, Washington, DC, 1930-1963: Director Nautical Almanac, 1948-1958, science director, 1958-1963; senior researcher associate, lecturer, Dept. of Astronomy, Yale University, 1963-1966, Professor of Astronomy, 1966-.