Manila Observatory and the international Jesuit geomagnetic research: Secchi, Perry, Juan, and Cirera

Agustin Udias, “Jesuits, Role in Geomagnetism” in Encyclopedia of Magnetism and Paleomagnetism edited by David Gubbins and Emilio Herrero-Bervera (Springer 2007), pp. 460-462.  (Pdf copy published by Springer. Type the title and it ranks first in the Google Search results).

The Jesuit order was suppressed in 1773 and restored in 1814. From this time work on geomagnetism was taken up again at the new Jesuit observatories (Udías, 2000, 2003). A total of 72 observatories were founded throughout the world. Magnetic stations were installed in 15 of them: five in Europe, one in North America, four in Central and South America, and five in Asia, Africa, and the Middle East. Some of those magnetic stations in Europe were among the first to be in operation. Observatories in Central and South America, Asia, and Africa provided for some time the only magnetic observations in those regions. Details of these observatories can be found in Udías (2003). At present, most of them have been either closed or transferred to other administration.

The first of these observatories was established in 1824 at the Collegio Romano (Rome). There, in 1858, Angelo Secchi (1818– 1878) began magnetic observations, using a set of magnetometers, a declinometer, and an inclinometer. He studied the characteristics of the periodic variations of the different components of the magnetic field and tried to relate magnetic variations with solar activity, considering the Sun to be a giant magnet at a great distance. Relations between geomagnetism and solar activity were to become a favorite subject among Jesuits.

In the same year, 1858, magnetic observations begun at Stonyhurst College Observatory (Great Britain). Stephen J. Perry (1833–1889, Figure J1) began his work on geomagnetism, carrying out three magnetic surveys: two in France in 1868 and 1869 and the third in Belgium in 1871 (Cortie, 1890). In each of these surveys, at each station, careful measurements were made of the horizontal component of the magnetic field, magnetic declination, and inclination or dip (Perry, 1870). In Belgium, Perry found large magnetic anomalies related to coal mines. In order to study the relation  between solar and terrestrial magnetic activity, which was still a controversial subject, Perry at Stonyhurst began a series of observations of sunspots, faculae, and prominences in 1881. For this purpose he installed direct-vision spectroscopes and photographic-grating spectrometers and made large drawings of the solar disk (27 cm diameter). Perry collaborated with Edward Sabine (q.v.) in this work. Perry participated in several scientific expeditions. The most important was to Kerguelen Island in 1874 to observe the transit of Venus; there he carried out a very comprehensive program of magnetic observations. His project of collecting and comparing all his magnetic and solar observations was never completed due to his untimely death during a scientific expedition to the Lesser Antilles to observe a solar eclipse. In 1874 he was elected a Fellow of the Royal Society for his work in terrestrial magnetism. Perry’s successor Walter Sidgreaves (1837–1919) completed the work and showed the correlation between magnetic storms and the maxima of sunspots (Sidgreaves, 1899–1901). The continuous magnetic observations from 1858 to 1974 at Stonyhurst may be one of the longest series at the same site.

The Manila Observatory (Philippines) was founded by Spanish Jesuits in 1865. Martín Juan (1850–1888) was trained in geomagnetism by Perry in Stonyhurst. Juan brought new magnetic instruments to Manila where he took charge of the magnetic section in 1887. In 1888, he carried out a magnetic field survey on various islands of the archipelago. His death did not allow him to finish the work; this was done in 1893 by Ricardo Cirera (1864–1932), who extended the survey to the coasts of China and Japan (Cirera, 1893).

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