Astronomer, b. at Macerata, States of the Church, 19 May, 1805; d. at London, England, 15 Nov., 1848. Entering the Society of Jesus at San Andrea, Rome, and showing peculiar aptitude for mathematics and astronomy, he was appointed professor of these branches at the Roman Collega and assistant to the director of the observatory, Father Dumouchel, whom he succeeded as director in 1839. Under his direction the observatory acquired a European reputation, and his labours in astronomy made him famous. Science owes to him many important discoveries. Unwearied in activity, he held correspondence with the most celebrated astronomers, and was a frequent contributor to scientific publications. He was a charter member of the Italian Society of Science, and was elected to membership in many scientific societies at home and abroad. He received the Lalande prizes of the French academy, and six times won the gold medal offered by the King of Denmark to the first discoverer of a telescopic comet. One of these medals is in the museum at Georgetown University, U.S.A. Father de Vico left Rome towards the end of March, the political disturbances of 1848 making his stay impossible. Arago, then Minister of Marine, wished to retain him at Paris, but the threatening outlook of affairs in Europe and the cordial invitation from Georgetown College to assume charge of its recently founded observatory impelled him to come to the United States. He arrived on 22 July, 1848, and, with characteristic activity, spent the whole of the first night with Lieutenant Matthew Fontaine Maury at the U.S. Naval Observatory, in Washington. The honourable reception, the frank and liberal treatment accorded him, and the generous offerings made to him, were powerful inducements to retain him in America, and he accepted the position of director of the observatory at Georgetown College. Clear-sighted and prompt in planning for future work, after a few weeks stay at Georgetown, he returned to England to expedite necessary business arrangements; at Liverpool he contracted typhus fever, and, although he recovered, his constitution had been undermined, and he fell into a decline.

As de Vico's most important works may be mentioned: "The Discovery of six Comets" (see Poggendorff, infra); "The Discussion of the Rotation-period of the planet Venus". the dispute between the periods of twenty-four days and twenty-three hours had been kept up for a century, and was settled by him by the important discovery that the spots on the planet Venus could be observed in the day-time, at least under the Italian sky. He gave the period twenty-three hours, twenty-one minutes, and twenty-two seconds, which was generally accepted until Schiaparelli (1890) maintained that the rotation coincided with the revolution, as is the case with our moon. De Vico's value was, however, justified, among others, by A. Muller (1898) and Belopolsky (1911). His various astronomical works are contained in the "Memorie" of the Roman College for the years 1836 to 1847, besides minor articles in the astronomical journals ("Comptes Rendus" and "Astronomische Nachrichten"). In addition to his scientific attainments, de Vico acquired reputation as a musical composer; his compositions were produced in the churches in Rome on the principal feasts, and his "Lamentations", published under the title "Antiphons and Responses of Matins and Lauds for the Last Three Days of Holy Week" (London, 1887) are famous in sacred music.

SECCHI in Memorie dei Osservatorio del Collegio Romano (1850), 131 sqq.; VOLPICELLI, Atti Acad. Nuovi Linceri, I, 172: POGGENDORFF, Handworterbuch, II, 1203; HERSCHEL, Monthly Notices of the Royal Astronomical Society of London, IX (1849), 65; SOMMERVOGEL, Bibliotheque de la Compagnie de Jesus, VIII, 642. See also L'Ami de la Religion, XCCCIC (Paris, 1849), 239-42.

E. I. Devitt.