ABBOT, CHARLES GREELEY (1872— ), American astrophysicist, was born in Wilton, N.H., on May 31, 1872. He graduated in 1894 from the Massachusetts Institute of Technology, and after a year of graduate study there joined the staff of the astrophysical observatory of the Smithsonian Institution. Here he served first as assistant, 1895-96, and then as acting director in charge from 1896 until 1907, when he was appointed director. He made original investigations in solar physics, studying espe cially theinfra-red solar spectrum, the solar constant of radiation, the variability of solar and terrestrial temperatures and the utili zation of solar heat. In connection with his researches he con ducted expeditions to observe total eclipses of the sun in 1900, 1901, 1908 and 1919. In collaboration with S. P. Langley he completed the mapping of the infra-red spectrum, published in the Annals (vol. i.) of the astrophysical observatory. With F. E.
Fowle and L. B. Aldrich he published also in the Annals (vol. iii., iv.) proofs of the variability of the sun, as shown by experiments conducted simultaneously in California and Algeria and from observations made in expeditions to Arizona and Chile. In recog nition of his discoveries he was awarded the Draper medal (1910) and the Rumford medal (1916). To scientific journals he has contributed numerous articles on the apparatus, methods and results of solar research. He published The Sun (1907), Every day Mysteries (1923) and The Earth and the Stars (1925). In 1918 he was made assistant secretary, and in 1928 secretary, of the Smithsonian Institution.