(b. Rolle di Cisón, Treviso, Italy, 10 July 1843; d. Padua, Italy, 7 July 1914)
astronomy, astrophysics, geodesy.
The son of an elementary school teacher, Lorenzoni received his degree in engineering at the University of Padua in 1863. In the same year, he entered the Padua Observatory as assistant to the director, Giovanni Santini. In 1872 he was appointed professor of astronomy at the University of Padua, where he also held the professorship of geodesy from 1869 to 1885. In 1878 he became the director of the Padua Observatory.
Lorenzoni’s first observations and research dealt with astrophysics. He began these studies with spectral analysis applied to the physical study of celestial bodies. As early as 1871, he collaborated with A. Secchi and P. Tacchini in establishing the Società degli Spettroscopisti Italiani and in the publication of its Memorie. During the total solar eclipse of 1870, which he observed in Terranova (now Gela), Sicily, he noted many brilliant lines of emission of the prominences, which led him to search for lines of emission besides those commonly visible in the chromosphere in full sunlight. Through this he discovered a new line that proved to be the 4471 A of the diffused series of the neutral helium of which he had measured the wavelength. Later he found that the same line had been independently observed by C H. Young in the United States. He then published in the Memorie delta Società degli spettroscopisti Italian important considerations on the spectroscopic visibility of monochromatic images. Among his writings on a variety of subjects published in the Memorie is an article dealing with theoretical optics, in which it is possible to foresee the invention of the spectroheliograph (1892) and the interferential filter(1929).
After abandoning spectroscopy, Lorenzoni turned to classical astronomy and the related science of geodesy, which occupied the greater part of his life. A keen observer who used instruments of very modest dimension, Lorenzoni observed several comets and small planets; and using Starke’s meridian circle, he continued and completed the stellar catalogs of his predecessors,
His numerous publications on classical astronomy discuss the formulas of precession and of nutation, in which the Euler equations for the rotation of a body around a given point are given by trigonometric and geometric methods.
Lorenzoni also dealt with fundamental formulas of spherical trigonometry used for calculating the parallax in the coordinates of a planet and for determining the angular coordinates by means of astronomical instruments.
In 1878 Lorenzoni was appointed a member of the Commissione Italiana per la Misura del Grado, which was then carrying on intensive geodesic activity. He made important contributions to the commission’s work on latitude and azimuth observations in various Italian localities. He also collaborated with Schiaparelli in Milan, with Oppolzer in Vienna, and with other foreign astronomers on telegraphic longitude determinations. His works on classical astronomy are found in the publications of the Commissione Geodetica Italiana.
Realizing the importance of measuring the force of gravity in Italy, especially in collaboration with scientific organizations established in other countries, the commission in 1880 aroused Lorenzoni’s interest in this problem. He soon presented a concrete plan of studies and the history of research to determine the length of the simple seconds pendulum. After having participated in a conference at Munich, where the subject was discussed, Lorenzoni was able to begin work in Italy. He had at his disposal a Repsold pendulum that he placed at the base of the Padua Observatory. His patient and accurate measurements and discussions of the problem were presented in a scholarly memoir published by the Accademia dei Lincei in 1888. It is divided into three parts; the first is theoretical; the second deals with the place of observation, instruments, and errors; the third presents the results of observation and reduction.
The value that Lorenzoni computed at Padua (sixty feet above sea level) of (he length of the seconds pendulum agreed completely with the value that he had obtained by reducing, for Padua, the values obtained at five other stations. From this he concluded that there were no great anomalies in the gravity at Padua. The site of these experiments was officially named the Sala di gravità di Giuseppe Lorenzoni and became the goal of geodetic scholars who use Padua for gravimetric reference and as a meeting place.
Lorenzoni’s fundamental research in gravity and the effect of support flection on the time of pendulum oscillation led to the design and construction of a bipendular support in a vacuum.
A fairly complete listing of Lorenzoni’s papers is in Royal Society Catalogue of Scientific Papers, VIII, 260; X, 632; and XVI, 870. The articles cited in the text are “Di un mezzo atto a rendere visibile tutta in una volta una immagine monocromatica completa delia cromosfera e delle protuberanze solare al lembo con la costruzione di lenti ipercromatiche,” in Memorie della Società degli spettroscopisti italiani, 3 (1874), 61-64, on theoretical Optics; and “Relazione sulle esperienze istituite … per determinare la lunghezza del pendolo sempliee …, in Atti dell’Accademla nazionale del LinceL Memorie, 5 (1888), 41-281.
Obituaries are by A. Abetti, in Vierteljahrsschrift der Astronomischen Geselhchaft49 (1914), 232-238; A. Antoniazzi, in Astronomische Nachrkhten, 198 (1914), col.486; and E. Millosevich, in Atti dell’ Accademia nazionale dei Lincei, 23 , pt. 2 (1914), 442-446.
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