SECCHI (Pietro Angelo). 1818-1878. Italian Jesuit priest. As - Lot 208

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, March 14, 1872. 4 pp. in-8. REMARKABLE SCIENTIFIC LETTER ON A SAND RAIN OBSERVED IN ROME AND ASSOCIATED METEOROLOGICAL PHENOMENA. A fascinating letter addressed to meteorologist Harold Tarry in which Father Secchi describes with great scientific precision an exceptional episode of sand rain in Rome. He describes the atmospheric circumstances preceding the phenomenon: "The sand rain was preceded in the morning by a yellowish sky, which led me to predict that it would fall...". The scientist explains that he immediately prepared collection devices to analyze the atmospheric deposits: "I gave orders to prepare containers to collect it, and white sheets of paper..." The letter contains important detailed barometric and meteorological observations: pressure variations, prevailing winds, atmospheric disturbances, state of the sky and evolution of air masses. Secchi also mentions several Italian locations affected by the phenomenon, including Perugia and Florence. One sheet contains an autograph drawing of the "barometric polygon", accompanied by handwritten numerical readings, a rare direct record of the great astronomer's scientific observational work. Secchi also describes the atmospheric effects of Saharan dust on the light spectrum and optical phenomena observed near the horizon: "The spectrum of the atmosphere before the rain was everywhere as seen near the horizon: broad bands at the less refrangible part..." A beautiful letter combining meteorology, atmospheric physics and scientific field observation, particularly representative of Father Secchi's research, a pioneer of modern meteorology and astrophysics. Usual folds and traces of use. Good overall condition.