An Observatory for “Physical Astronomy”

Chapter 3 Establishing the New Collegio Romano Observatory: An Observatory for “Physical Astronomy”

Despite having a centuries-old astronomical tradition, an observatory was only installed at the Collegio Romano after the suppression of the Society of Jesus in 1773. Construction began in 1787, thanks to the support of several prelates, especially the influential cardinal Francesco Saverio de Zelada (1717–1801), when a tower was built for establishing an observatory, and several astronomical and meteorological instruments were gradually placed on its top. The director of the observatory was the priest Giuseppe Calandrelli (1749– 1827), who oversaw research until 1824, when the Collegio Romano was given back to the Society of Jesus, which had been reconstituted by Pius vii in 1814. Calandrelli was then charged with building another observatory, established in 1827 and located in the Roman seminary, at the Campidoglio palace. The coexistence of the two observatories reinforced the Roman astronomical tradition.1 In 1824, once the Collegio Romano had been returned to the Jesuits, Eti- enne Dumouchel, S.J. (1773–1840), De Vico, and Brother Bernardino Gambara (1814–84) were respectively appointed director, assistant, and keeper (acting as second assistant). One year later, Superior General Luigi Fortis (1748–1829, in office 1820–29) donated a Cauchoix telescope, which De Vico would later use to discover the returning Halley’s Comet, thereby gaining an international reputation both for the observatory and for himself. De Vico became director in 1839; his studies on planets, satellites, and comets consolidated the scientific renown of the observatory.2 Now it was up to Secchi to build on the reputation of his predecessors.

1 For more information on the astronomical observatories in Rome from the seventeenth to the nineteenth century, see Roberto Buonanno, Il cielo sopra Roma: I luoghi dell’astronomia (Milan: Springer-Verlag, 2008). 2 On the early years of scientific activity at the Collegio Romano Observatory, see Sabino Maffeo, The Vatican Observatory: In the Service of Nine Popes (Rome: Libreria Editrice Vaticana, 2001), 8–14.

44 Chapter 3

FIGURE 3.1 The old observatory in the Calandrelli Tower. From Giuseppe Calandrelli and Andrea Conti, Opuscoli astronomici (Rome: Stamperia Salomoni, 1808), title page (detail). 1 In Need of a New Observatory

Secchi’s first task was to recover the two main instruments belonging to the observatory, which had been moved by De Vico to be preserved during the ex- ile of 1848, namely the above-mentioned Cauchoix telescope, whose objective lens was returned from the United States in November 1850, and another telescope, a meridian circle by Ertel, used for observing the transit of the stars on the meridian and donated in 1842 by Superior General Roothaan. The observatory’s equipment also included a Gambey theodolite (an altazimuth instru- ment, for measuring angles), two Dent astronomical pendulums,3 and a few

3 The pendulums—series no. 956 and no. 1832—were donated by Gregory xvi and Secchi’s assistant, Fr. Rosa (see below).