Ad principem Franciscum Estensem … de Cometa anni 1652 & 1653.

Modena: Bartolomeo Soliani, 1653.

First edition, exceptionally rare, of the remarkable first publication of the great observational astronomer Gian Domenico Cassini, in which he demonstrated for the first time by observing their parallax that comets are celestial phenomena and not, as Aristotle had claimed, ignited exhalations from the earth (the comet is now designated C/1652 Y1). We have been unable to trace any other copy of this work in commerce, and only a handful of institutional copies. In 1652, just before Christmas, a comet was observed approaching the Earth, and it remained visible through the first week of January 1653. Cassini was then a guest in the astronomical observatory of his patron, the Marquis Cornelio Malvasia, inside the Villa di Panzano, near Castelfranco Emilia. Here, together with Malvasia and, occasionally, the Duke of Modena, Cassini spent many cold winter nights taking, with the observatory’s telescope, accurate measurements of the comet’s position, and elaborating a theory on its origin: “the observations I made [of the comet] authorized me to conclude that it had no sensible parallax and that it was above [the orbit] of Saturn.” Each of Cassini’s observations is accompanied by an engraved illustration in the text showing the position of the comet with respect to certain reference stars. The last two pages are dedicated to the description of the instrument at Panzano, illustrated on a beautiful engraving, used to determine the position of the comet with respect to these reference stars. The operation of the large instrument required two observers and several assistants. “From a series of observations on the comet of 1652, made with the Marquis of Malvasia, who had been instrumental in bringing him to Bologna, he concluded that comets were not of a meteoric nature as had been imagined, but that they were guided in their paths by the same laws as the planetary bodies; and he explains the motion of the comet by a circle described around the earth and beyond the orbit of the moon. These observations were published in his first production, which appeared in 1653, under the title of De cometa anni 1652 et 1653” (Brewster, The Edinburgh Encyclopaedia (1830), p. 603). The comet of 1652 was also observed by Hevelius in Gdansk between December 20 and January 8; Hevelius devotes the whole of the first book of his Cometographia (1668) to this comet: “he had an ingenious but inaccurate way of judging parallax and greatly underestimated the comet’s distance … He supposed comets to be condensed planetary exhalations” (DSB). The comet’s true parabolic orbit was calculated by Edmond Halley in his Synopsis (1705), using 54 observations (including those of Cassini). OCLC lists five copies worldwide (Brown, Adler Planetarium, Oklahoma, Bayerische Staatsbibliothek, Institut de France); KVK adds the Archiginnasio Municipal Library, Bologna, and University of Florence, and there is also a copy in the Astronomical Observatory in Brussels; not on COPAC (not in the British Library).

The first of a family of astronomers who settled in France and were prominent in directing the activities of the French school of astronomy until the Revolution, Cassini (1625-1712) … studied at Vallebone and then at the Jesuit college in Genoa and at the abbey of San Fructuoso. He showed great intellectual curiosity and was especially interested in poetry, mathematics, and astronomy. He was attracted at first by astrological speculations, but reading Pico della Mirandola’s pamphlet Disputationes Joannis Pici Mirandolae adversus astrologiam divinatricem persuaded him of the frivolity of that pseudoscience. Yet, paradoxically, the beginning of his scientific career benefited from the reputation he acquired for his knowledge of astrology. The Marquis Cornelio Malvasia, a rich amateur astronomer and senator of Bologna who calculated ephemerides for astrological purposes, invited him to come to work in his observatory at Panzano, near Bologna … Thanks to the marquis’s aid, he made use, from 1648, of several instruments that allowed him to begin his first researches. He was also able to complete his education under the tutelage of two excellent scientists, the Bolognese Jesuits Giovan Battista Riccioli—who was then finishing his great treatise, the Almagestum novum (1651)— and Francesco Maria Grimaldi, who later became famous for his discovery of the phenomenon of diffraction, published in his posthumous work De lumine (1665). Although one cannot exactly determine their influence on the young Cassini, it appears that they convinced him of the importance of precise and systematic observation and of the necessity of a parallel improvement in instruments and methods. They probably likewise contributed, less happily, to making him wary of the new theories—especially of Copernicus’ system—and to reinforcing in him the conservative tendencies that he displayed throughout his life.With his first works Cassini won the esteem of his fellow citizens to such an extent that in 1650 the senate of Bologna, on the recommendation of its patron, designated him to occupy the principal chair of astronomy at the university, which had been vacant since Bonaventura Cavalieri’s death in 1647 … In 1652–1653 the passage of a comet attracted his attention” (DSB)

“In 1652, just before Christmas, a comet was noticed approaching the earth. From the city of Bologna, it was visible at the zenith, and it was observed also by the archbishop of the city. As reported by Cassini in his memoirs, this circumstance required again his presence at the castle of Panzano, by request of Malvasia: ‘the Marquis Malvasia absolutely wanted that I come with him and my student Beringelli Geri to his home in Panzano’.

“Cassini thus relocated to the Panzano castle, far from the city, which actually hosted a very well-equipped observatory that would enable him to make better observations. One can appreciate the sophistication of this observatory by the quote of Cassini, who denoted this place as ‘an Italian Uraniborg’, namely the castle of the Danish astronomer Tycho Brahe, which about 60 years before had become famous as the most advanced observatory of the time … In this observatory, he was also able to use new tools built especially for the occasion. His plan was to follow the comet’s movement night after night and to determine its latitude and longitude. Duke Francis of Modena, a curious man interested in astronomy, was among the guests participating in some of the observations, and Cassini dedicated the work that was completed after his observations to him: De Cometa anni 1652 et 1653 [The comet of the year 1652 and 1653].

“Indeed, Cassini crafted a remarkable work, and in this publication he gave detailed observational data, which included drawings of the comet’s positions with respect to the constellations. This work also included the author’s personal considerations about comets, a subject that he will study for a lifetime.

“As an example of such considerations and of their importance in the scientific debate of the time, it can be mentioned that Cassini stressed that the comet, which passed at the zenith and at the end of his observations was above Saturn, had no significant parallax. This, in other words, meant that it was quite far from the Earth …

“The apparatus used for observing the comet night after night is described and depicted in the publication. It was a large instrument made of wood and with the shape of a compass. The angle between the two legs was adjusted in order to make each of them point to one of a pair of stars. Then, the angle between these two objects was estimated thanks to a series of mobile and fixed parts connected by screws. This particular tool appears in Cassini’s publication in response to the expressed wish of Marquis Malvasia.

De Cometa anni 1652 et 1653 was the first scientific study written by Cassini, and it also the only one rrporting the Ligurian origin of the scientist, who is denoted as ‘Jo. Dominicus Cassinus genuensis in Bononiensi Archigymnasio publicus Astronomiae Professor’ [Gio. Domenico Cassini, from Genoa, public Professor of Astronomy at the Archigymnasio of Bologna].

“Actually, the genesis of the work is quite peculiar. It stems from the competition for the paternity of scientific discovery, and possibly, from the academic rivalry between the university and the Jesuits.

“Marquis Malvasia immediately gathered in his castle some printers from Modena, so that the tables could be printed as soon as the data and the drawings were collected. This provided a decisive advantage over the competitors with respect to the publication of the results.

“Indeed, in the introduction Cassini reports that the comet appeared on December 20th, at the fourth hour of the night, between the Pleiades and the constellation of Taurus, close to the neck of the Bull: ‘Ibi igitur die vigesima hora noctis quarta observavimus Cometam cum Pleiadibus, et cum stella proxima in collo Tauri talem officere configurationem’. These words are dated January 6, 1653, and a very short time later appeared the printed version of the book, which was immediately sent to Prince Leopoldo de’ Medici in Florence, … just days before the arrival of a similar work by the Jesuits [probably David Christiani’s Tractatus physico-astronomico-historicus … de cometa qui A.C. 1652. orbi elluxit …, Giessen, 1653].

“Finally, in a draft letter written by Cassini to an unknown recipient after the publication of De cometa, the Italian scientist emphasized the mathematical and astronomical basis of his work. In particular, he explicitly rejected any astrological considerations, and it seems that he also intervened to reassure people who were terrified by the arrival of the comet” (Bernardi, pp. 25-27).

Following his observations of the comet of 1652/3, Cassini continued his astronomical work. “In 1659 he presented a model of the planetary system that was in accord with the hypothesis of Tycho Brahe; in 1661 he developed a method, inspired by Kepler’s work, of mapping successive phases of solar eclipses; and in 1662 he published new tables of the sun … In 1664 Cassini published an observation of a solar eclipse made at Ferrara. The study of comets, however, continued to hold his special interest. In 1664–1665 he observed one of them in the presence of Queen Christina and formulated on this occasion a new theory (in agreement with the Tychonian system) in which the orbit of the comet is a great circle whose center is situated in the direction of Sirius and whose perigee is beyond the orbit of Saturn” (DSB).

Cassini departed Bologna for Paris on February 25, 1669, invited by Colbert to help set up and become the first director of the new Paris Observatory. Cassini spent the remainder of his career in Paris, where he founded an astronomical dynasty, which included his son, Jacques, or Cassini II (1677–1756); his grandson César-François, Cassini III (1714–1784), and his great grandson, Jean-Dominique, Cassini IV (1748–1845). Cassinis I-IV served as the first four directors of the Paris Observatory.

Lalande, Bibliographie astronomique, p. 235 (“C’est ici le premier ouvrage du célèbre Dominique Cassini”); Poggendorff I, 388f; Riccardi I, 275.1 (describing the copy at the University of Bologna); not in Houzeau & Lancaster. Bernardi, Giovanni Domenico Cassini: A Modern Astronomer in the 17th Century, 2017.

Folio (290 x 205 mm), pp. [iv], 28, [2], with one folding engraved plate showing the instrument and 13 text engravings (minor browning). Later calf (a little rubbed).

Item #5203

Price: $38,500.00