Pietro Angelo Secchi, an Italian astronomer, born in Reggio in Emilia, July 29, 1818. He became a Jesuit Nov. 3, 1833, studied mathematics under Padre de Vico, and taught physics in the college of Loreto from 1841 to 1843. In 1844 he began his course of theology in the Eoman college, completed it at Georgetown college, D. C., in 1848-9, and taught physics and mathematics there till the autumn of 1850, when he was recalled to Rome. He was then appointed director of the observatory of the Roman college, reconstructed it on a new site and plan, invented and perfected a system of meteorological observation, published a monthly bulletin continued till 1873, and constructed a meteorograph much admired at the Paris exhibition of 1867. He was commissioned by Pius IX. to complete the trigonometrical survey of the Papal States begun by Boscovich in 1751, and to rectify the measurements already made of the meridional arc, and executed successfully a commission to bring a supply of water to Rome from Frosinone, 48 m. distant. The results of his labors in every field of astronomical research since 1850 are chronicled in the scientific periodicals of Italy, France, Germany, and England. He is especially distinguished for his discoveries in spectroscopic analysis and in solar and stellar physics.
After the closing of the Roman college and the expulsion of the Jesuits (1870-73) Secchi was allowed to retain his post, continued to lecture on astronomy in the ecclesiastical schools of Rome, and in 1875 he was sent by the Italian government on a scientific mission to Sicily. Among his important publications are: "Researches on Electrical Rheometry," originally in the "Smithsonian Contributions to Knowledge" (Georgetown, 1852); Quadro fisico del sistema solare secondo le più recenti osserva-zioni (Rome, 1859); Catalogo delle stelle (Paris, 1867); Sugli spettri prismatici delle stelle fisse (Rome, 1868); Le recenti scoperte astronomiche (1868); Nove ricerche sulle protuberanze solari (1869); Sur l'influence de l'atmospère sur les rates du spectre et sur la constitution du soleil (1869); Fisica solare: suite ultime scoperte spettroscopiche fatte nel sole (1869); "Spectrum Observations on the Rotation of the Sun" (London, 1870); Le soleil: exposé des principales découvertes modernes sur la structure de cet astre, son influence et ses relations avec les autres corps celestes (Paris, 1870; German translation by Schellen, Brunswick, 1872); and Dell' unità delle forze fisiche (Rome, 1875; French translation, Paris, 1875).