Due secoli di strumenti geomagnetici in Italia, 1740-1971 (Two Centuries of Geomagnetic Instruments in Italy, 1740-1971)

Abstract

Reviewed by: Due secoli di strumenti geomagnetici in Italia, 1740–1971* Roberto Mantovani (bio) Due secoli di strumenti geomagnetici in Italia, 1740–1971. Edited by M. Basso Ricci et al. Bologna: Editrice Compositori, 1997. Pp. 234; illustrations, English summary. This book provides a first national census and a first homogeneous list of the remarkable instrumental geomagnetic patrimony present in Italy. The contributors are historians of physics at the University of Milan (coordinated by Pasquale Tucci) who for some time have engaged in the reconstruction of historical events and contributions of a scientific discipline rather neglected in Italy: geomagnetism. The work finds its starting point in the historical reconstruction of geomagnetic studies that occurred during the first half of [End Page 404] the nineteenth century in Milan at the Astronomic Observatory of Brera. In fact, this observatory was included by Carl Friedrich Gauss in an 1836 program of international cooperation—the Magnetische Verein—that intended to study, by means of an exact operative protocol prescribed by Gauss, the spatial and temporal variation of the horizontal component of the magnetic field of the earth on the whole terrestrial globe. The study of the scientific contribution furnished by the astronomers of Brera to Gauss’s project induced the historians of Milan to inquire into the activities of the other Italian scientific institutions in the field of geomagnetism. The methodological choice resulted not in a collection of personages, studies, or memories on geomagnetism in Italy (though such a collection is to be hoped for) but in a national census of geomagnetic instruments. This approach makes it clear that a careful consideration of scientific instrumentation, as these authors have rightly highlighted, can yield a profitable historiographical contribution for understanding routine procedure and the development of scientific theories, as can scientists’ documentary material. The book opens with a short summary written in English, then essentially consists of two parts: the first (less substantial) describes to readers, in two synthetic chapters, the historical context of the origin of geomagnetism and provides a panoramic picture of the most up-to-date knowledge of the discipline; the second (more substantial) contains the instrument catalog, a compilation of seventy-nine classification cards. The catalog has been compiled by Maria Basso Ricci, and it covers the period from 1740 to 1971. The census has allowed the classification of about two hundred instruments and has involved sixty-five scientific institutions scattered on the Italian territory. The instruments are classified in five sections (inclinometers, declinometers, declinometers-inclinometers, magnetometers, and integrated magnetic apparatus) according to the type of measurement (inclination, declination, magnetic intensity) and the terms of measurement that can be performed (absolute or daily variation). Each section is preceded by helpful historical data about the typologic evolution of the instrument. Each classification card describes the instrument and provides information on its principle of functioning and on its method of measurement, and each is accompanied by a color photograph. The catalog describes instruments of certain historical importance connected, for example, with the constitution of the first meteorological and geomagnetical international networks. A Brander’s declinometer from the Department of Astronomy of the University of Bologna was certainly used by the astronomers of Bologna between 1781 and 1792 within the limits of the most important meteorologic grid of the eighteenth century, as suggested and arranged by the Palatine Society of the Academy of Sciences of Mannheim. The Astronomic Observatory of Brera is in possession of one magnetometer built by Gauss in 1835. The instrument was employed during the [End Page 405] years 1836–45 by the astronomers of Milan within the limits of the Magnetische Verein. The catalog also describes the first unifilar variational declinometers that appeared in Italy after the one described by Coulomb (1777) as well as some nineteenth-century instruments utilized by important Italian scientists such as the Jesuit Father Angelo Secchi (who founded a magnetic observatory in Rome at the Roman College in 1859) and the Barnabite Francesco Denza, author in the years 1871–88 of the first magnetic survey carried out in Italy. The catalog also describes numerous models of magnetometer of the first half of the twentieth century. Roberto Mantovani Dr. Mantovani is curator of the Collection of Historical...