SECCHI (Pietro Angelo). 1818-1878. Italian Jesuit priest. As - Lot 207

SECCHI (Pietro Angelo). 1818-1878. Italian Jesuit priest. Astronomer, astrophysicist and meteorologist. Director of the Roman College observatory. L.A.S. "P. A. Secchi" to Harold Tarry. Rome, July 5, 1873. 4 pp. in-8. IMPORTANT SCIENTIFIC LETTER ON SUNSPOTS AND THE CHROMOSPHERE. A fascinating letter to meteorologist and astronomer Harold Tarry in which Father Secchi develops his theories on the nature of sunspots and the movements observed in the photosphere. He discusses the "vortex" theory applied to sunspots and responds to the hypotheses then supported by several contemporary scientists: "You ask me if I believe that sunspots can still be vortices...". Secchi analyzes the rotatory and translatory movements observed in sunspots, as well as the phenomena of solar flares: "rotatory motion may exist around the spot itself in the photosphere..." The letter contains a remarkable development on the chemical composition of sunspots, mentioning hydrogen, sodium, calcium, chromium and iron, as well as their movements in the solar atmosphere. The scientist also criticizes Respighi's positions on the chromosphere: "I persist in saying that M. Respighi is mistaken in denying the presence of the chromosphere on the spots..." One of the leaves is enriched with a small autograph diagram showing a double vortex connecting two large sunspots, a rare scientific illustration drawn in Secchi's hand. A very important letter for the history of solar astrophysics and the beginnings of astronomical spectroscopy, bearing witness to the scientific debates surrounding the structure of the Sun in the 19th century. Folds and minor traces of use. Good condition.