TODD, David Peck, astronomer, born in Lake Ridge, New York, 19 March, 1855. He entered Columbia, but, was graduated at Amherst in 1875, and appointed chief assistant to the United States transit of Venus commission in Washington. For three years he was engaged in reducing the observations of the transit of 1874, and his result for the parallax of the sun-8",883--was the first, that was derived from the American photographs of that transit. When at Amherst he began a series of observations of the satellites of Jupiter, which was assiduously maintained for twelve years, or during an entire revolution of the planet. His observations on those bodies led him to begin theoretical researches on their orbits, and he published "A Continuation of De Damoiseau's Tables of the Satellites of Jupiter to the Year 1900" (Washington, 1876). These are now used in the preparation of the "American Ephemeris," the "Berliner astronomisches Jahrbuch," and elsewhere, and they were also extended backward by him to 1665. In 1.877 he began to study the possibility of an extra-Neptunian planet, from the discrepancies in the motion of Uranus; after which he spent several months in the optical search for it, and he is at present examining the photographic evidence of its existence. In 1878 he was sent to Texas in charge of the United States government expedition to observe the total eclipse of the sun on 29 July, and on his return was appointed assistant to Simon Newcomb in the preparation of the "American Ephemeris and Nautical Almanac," remaining in that office until 1881. He then accepted the chair of astronomy at Amherst, with the directorship of the observatory, which appointment he still holds, and in 1881-'7 he was professor of astronomy and higher mathematics at Smith college, where in 1885-'7 he was intrusted with the planning and construction of the new observatory. Professor Todd was invited by the trustees of the James Lick estate to direct the observations of the transit of Venus in 1882 from the Lick observatory, and in 1887 he was placed in charge of the expedition to Japan under the auspices of the National academy of sciences and the United States navy department to observe the total solar eclipse of 19 August After that event he organized an expedition to the summit of Fujiyama, the sacred mountain of Japan, 12,500 feet in elevation. Astronomical and meteorological observations were made from the summit, which have an important bearing on the occupation of such peaks for scientific purposes. The degree of Ph.D. was conferred on him by Washington and Jefferson college in 1888, and he is member of scientific societies both at home and abroad. His writings include contributions to the transactions of societies of which he is a member and reports to the government.