Abstract
Giovanni Domenico Cassini (1625–1712) was the first of a dynasty of four Cassinis who ruled the Paris Observatory from father to son, from 1669 to the French Revolution.He was already a famous astronomer who had worked at different places in Italy, especially in Bologna, when he was called to France “to make astronomy serve the improvement of geography and navigation” according to his own words (quoted in Cassini IV, p. 291, see below). He acquired French citizenship, changed his first name to Jean-Dominique, and married a French woman. He and his collaborators were the first to determine longitudes using eclipses of Jupiter’s satellites. From this and their own triangulations, they started constructing an accurate map of France that was progressively completed by the three successive Cassinis. Cassini I was a first-class observer; in spite of the practical difficulties of observing at that time with very long, often tubeless telescopes, Cassini produced the best drawings, before photography, of the Moon and Jupiter, determined the period of rotation of Jupiter and Mars, discovered four satellites of Saturn, etc. Clearly, he deserves a biography and Gabriella Bernardi’s book is the first rather complete one.
The book covers mainly the life and work of Jean-Dominique Cassini, but also more briefly treats those of his successors and the two Maraldis, who worked with them in Paris. It is generally well written, well illustrated, lively, and accurate, in spite of a few errors; for example, Christiaan Huygens never served as chair of the French Academy of sciences (p. 62), although he played a prominent role in this institution. Neither Cassini I nor Cassini II had the title of Director of the Observatory (p. 115). It was not Tycho Brahe who invented triangulation but rather Gemma Frisius, half a century earlier (p. 103). Worse, the text is plagued by many misprints and inaccurate transcriptions, sometimes leading to misunderstandings, especially in the French texts. The bibliography is incomplete, ignoring, for example, the important book edited by Paul Brouzeng and Suzanne Débarbat, Sur les traces des Cassini, Paris, Ed. du CTHS, 2001, which contains much information, especially on the scientific activities of Giovanni Domenico in Bologna.
A big problem for readers not fluent in French is that many of the texts are not translated into English. This is the case in the five appendices. Publishing the French or Italian texts of these appendices is of no special interest, because they can all be obtained freely at the Gallica pages of the Bibliothèque Nationale de France (gallica.bnf.fr) as parts of Jean-Dominique Cassini’s (Cassini IV) Mémoires pour servir à l’histoire des sciences et à celle de l’Observatoire de Paris, Paris, Bleuet, 1810. They can also be obtained through Google Books. It would have been much more useful to translate them into English and even better to translate the whole of the Anecdotes de la vie de J.-D. Cassini, rapportées par lui-même (pp. 255–309 of this book).
In spite of these reservations, however, Bernardi’s book makes for pleasant reading and can be recommended.