CASSINI, Giovanni Domenico.

Sammelband of seven exceptionally rare works. I. Specimen observationum Bononiensium, quae novissime in D. Petronij templo ad astronomiae novae constitutionem haberi oepere. Videlicet observatio aequinoctii verni anni MDCLVI ... Cui praepositae, & adiectae sunt aliae ad huius complementum pertinentes. Ex quibus multa incerta in theoria solis deteguntur ... Motosque solis realis inaequalitas nunc primum immediatis observationibus detegitur ... Bologna: eredi di Evangelista Dozza, 1656. II. Theoriae motus cometae anni 1664 pars prima. Ea praeferens, quae ex primis observationibus ad futurorum motuum praenotionem deduci potuere, cum nova investigationis methodo, tum in eodem, tum in comete novissimo anni 1665 ad praxim revocata … Rome: Fabio Di Falco, 1665. III. Lettere astronomiche di Gio. Domenico Cassini al Signor Abbate Ottavio Falconieri sopra il confronto di alcune osservazioni delle comete di quest’anno 1665. [Colophon:] Rome: Fabio di Falco, 1665. IV. Lettera astronomica di Gio: Domenico Cassini al Sig. abbate Ottavio Falconieri. Sopra l’ombre de Pianetini Medicei in Giove. [Colophon:] Rome: Fabio Di Falco, 1665. V. [Drop-title:] Lettere astronomiche di Gio. Domenico Cassini al Sig. Abbate Ottavio Falconieri sopra la varietà delle macchie osservate in Giove e loro diurne rivoluzioni. [Rome: Fabio di Falco, 1665]. VI. Tabulae quotidianae revolutionis macularum Iovis. Nuperrimè adinventae a Ioanne Dominico Cassino … Rome: Fabio Di Falco, 1665. VII. Martis circa axem proprium revolubilis observationes. [Colophon:] Bologna: eredi di Evangelista Dozza, 1666.

Bologna & Rome: Dozza & Di Falco, 1656-1666.

An extraordinary sammelband containing the first editions of seven exceptionally rare works documenting Cassini’s very accurate observations of the motion of the Sun relative to the Earth, which enabled him to confirm Kepler’s second law, of the comets of 1664-5, of Jupiter’s spots, including his discovery of the Great Red Spot, and the first detailed illustrations of Mars, which enabled him to determine the rotation periods of these two planets – all made possible by his new collaboration with the lens makers Eustachio Divini and, most importantly, Giuseppe Campani. The first work records numerous observations made by Cassini using a new ‘meridian’ he had constructed (essentially a large sundial). These include measurements of the obliquity of the ecliptic, and the exact position of the solstices and the equinoxes, and, most importantly, of the speed of the sun’s apparent motion and the variation of its diameter. These latter measurements enabled Cassini to confirm the validity of Kepler’s second law of motion, thus disproving one of the main statements of the geocentric model, namely that of uniform motion along circular orbits. The next two works document Cassini’s observations of the comets of 1664-5, which were observed by many astronomers, including Auzout, Borelli, Fabri, Hooke, Hevelius, Petit, and Newton as a student. The Theoriae motus “is very important because it is the first that reports a precise sequence of observations and the entire path of a comet, also supported by mathematical calculations” (Bernardi, p. 47). Cassini observed the comets “in the presence of Queen Christina [to whom the first work is dedicated] 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). The large engraved plate depicts the course of the comet in the southern celestial hemisphere from December 13, 1664 through the middle of January 1665; it also shows the appearance and direction of the comet’s tail. Cassini’s detailed observations were made with a powerful new telescope made by Giuseppe Campani, which he describes in the preface to the first work. “Through his friendship with the famous Roman lens-makers Giuseppe Campani and Eustachio Divini, Cassini, beginning in 1664, was able to obtain from them powerful celestial telescopes of great focal length. He used these instruments—very delicate and extremely accurate for the time— with great skill, and made within several years a remarkable series of observations…” (ibid). The third work, addressed to the archaeologist Falconieri, presents further observations on the comet, and Cassini’s remarks about the observations made by Auzout and Hevelius. “In July 1664 [Cassini] detected the shadow of certain satellites on Jupiter’s surface and was thus able to study the revolution of the satellites” (ibid.). These observations are reported in the fourth work in our sammelband. “A controversy about the results of these observations started quite soon. First, someone from Rome observed one dark shadow and another less dark one. Cassini clarified that the latter was not the shadow of a satellite but rather a physical spot on the planet. To prove his statement … he observed that it did not follow the movement of any orbiting body, and that it appeared every 9 hours 56 min, which the astronomer attributed to the rotation period of the planet … In support of the statement of the Italian scientist, Abbot Ottavio Falconieri published the letters between Cassini and himself as proof of his past observations, and Cassini made public his predictions on the return of the spot on Jupiter, to dispel any doubts” (Bernardi, p. 53). This was the discovery of the Great Red Spot (although Cassini was unable to discern the Spot’s red colour due to the limitations of his instruments). These letters were printed in the fifth work in the present volume. This may have been issued with the sixth work, which contains tables of the ‘revolutions’ of Jupiter’s spots. In the last work, Cassini carried out similar observations of Mars, observing spots on its surface which enabled him to determine its rotation period, which is almost the same as that of the Earth. The remarkable drawings in this work are the first detailed illustrations of Mars and the first to show the bright polar cap at the Martian north pole. All of these works are of great rarity. OCLC lists in the US, two copies of I (Cornell, Linda Hall), one copy of II (Brown, lacking plate), three copies of III (Brown, Cornell, Ohio State), one copy of VII (Oklahoma), and none of the other three works. Library Hub adds two copies of III and one each of I, II, IV-VII. ABPC/RBH: in addition to the present volume, Bolaffi 2014 (II & III, bound together); Sotheby’s 2004 (V, Macclesfield), and no other copies of the remaining works.

Widely regarded as the greatest observational astronomer of the 17^th century after Kepler and Galileo, Cassini was born in Perinaldo, Republic of Genoa. “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. In accepting this position Cassini initiated the first part of his career, which lasted until his departure for France in February 1669. Thanks to the marquis’s aid, he thus 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” (DSB).

“Since the determination of certain essential astronomical data is tied to the movement of the sun (solstices, obliquity of the ecliptic, and so forth) and thus requires the daily observation of the height of that body at the time of its passage to the meridian, astronomers for a long time had tried to increase the precision of these observations by employing high structures – churches in particular – as supports for large sundials, called meridians. Such was the case at the church of San Petronio of Bologna, where an important meridian had been constructed in 1575 by a predecessor of Cassini in the chair of astronomy at the university, Egnatio Danti. Unfortunately, structural modifications necessitated by the enlargement of the church had recently rendered this meridian unusable by blocking the orifice through which the solar rays entered. In 1653, Cassini, wishing to employ such an instrument, sketched a plan for a new and larger meridian but one that would be difficult to build. His calculations were precise; the construction succeeded perfectly; and its success made Cassini a brilliant reputation.

“During the following years Cassini made with this meridian numerous observations on the obliquity of the ecliptic, on the exact position of the solstices and the equinoxes, on the speed of the sun’s apparent motion and the variation of its diameter, and even on atmospheric refraction; for all these phenomena he provided increasingly more precise measurements. His principal observations, published in Specimen observationum Bononiensium… (1656), are dedicated to Queen Christina of Sweden, then in exile in Italy” (DSB).

The most important application of these observations was to confirm the validity of Kepler’s second law of motion, according to which a planet moves in its ellipse so that the line between it and the Sun placed at a focus sweeps out equal areas in equal times. Kepler’s first law, that the planets follow elliptical orbits, “implies a variation of the apparent speed of the Sun and of its diameter of the same purely geometrical nature of that of the geocentric model. However, when it comes to the second law, one has to admit that the speed has an additional decrease due to the slowing down of the physical motion of the Sun. By simple geometric considerations, in the case of uniform motion hypothesized in the geocentric (and Copernican) model(s), the decrease of the apparent speed while moving from the perigee to the apogee is just proportional to the apparent diameter of the Sun. In the Keplerian model, instead, the Sun slows down also from a physical point of view, which means that its apparent speed decreases more that its diameter … The meridian line works like a darkroom, and that the projection of the Sun on the floor is not point-like, but rather a disk. From its dimension, therefore, it is possible to estimate the apparent diameter of the Sun and, if the instrument is accurate enough, to discern between the two cases.

“In practice, with his observations at the meridian line of San Petronio, the Italian astronomer proved that the solar-motion difference in speed during the year is not just proportional to the change of its diameter. Therefore, the additional physical change postulated by Kepler was real and in agreement with his second law … the observations proved the validity of the second law of planetary motion, and thus definitely disproved one of the main statements of the geocentric model, namely that of uniform motion along circular orbits. The importance of this fact cannot be underestimated since, as mentioned in the above excerpt, this was considered false by many astronomers like the Jesuit father Riccioli.

“To sum up, Cassini used the observations at the meridian line to estimate the value of the obliquity of the ecliptic, and to demonstrate experimentally the validity of Kepler’s second law. In doing so, he studied the atmospheric refraction, discovering that Tycho’s model had to be corrected. He also obtained significant results about the solar parallax and the determination of the Earth’s circumference. In 1656, he published an essay of his observations entitled Specimen Observationum Bononiensium quae novissime in D. Petronij templo ad Astronomiae novae constitutionem haberi coepere” (Bernardi, pp. 34).

The next two works, II and III, describe observations of the comets of 1664 and 1665. “The comet of 1664 was discovered in Spain on November 17, 18 days prior to perihelion. It reached its greatest apparent brightness on December 29, when it passed within 17 astronomical units, AU, of Earth … Due to its proximity to Earth at that time, the comet reached an impressive apparent magnitude of –1, with its tail reaching nearly 40 degrees in length … Only one month after the comet of 1664 was last sighted retreating from the Sun, the less impressive comet of 1665 was discovered at Aix in southern France. It quickly moved into the glare of the Sun and was last seen on April 20, 1665, four days before reaching perihelion” (Yeomans, pp. 69-70).

“As Cassini (1625-1712) writes in his memoirs, during the stay in Rome, at the end of 1664, there appeared ‘a comet next to the beak of the Crow constellation’ (another one became visible in April 1665) … Prince Mario Chigi, the Pope’s brother, notified Cassini of the appearance of the comet, so he could observe it regularly beginning on December 18, 1664, from Chigi Palace, aided by an abbot to record its position with respect to the nearby stars. The cometary path was then represented on the prints by adding small grains of lead to the print master of a stellar map. This comet and the next one, in 1665, are scientifically very important because their regular observation and the consequent calculation of the ephemerides allowed Cassini to formulate his theory about cometary motion, started years before in the Panzano observatory but never finished. His patron, the Marquis Malvasia, died in March 1664, but their research continued with the observation of the newly visible comets with the help of new collaborators.

“In Rome, this observational program continued not only from the Chigi Palace, but also with Queen Christina of Sweden, in her residence. At her invitation, the astronomer and Cardinal Assolini (who would become her sole heir) went here every day to pay a visit to the noble woman, and, before the observations, they discussed science to the great pleasure of Christina. In this regard, Cassini reports in his memoirs that, in these discussions, the Queen was often inclined to side with his opinions so, as a man of the world, the Italian scientist was used to trying to move the conversation to topics that would be more pleasing to the eminence.

“His attempts, however, had little success, since most of the time the Queen was quite curious about the comet, and she wanted to follow it with Cassini. She made clever comments and posed questions, for example, noticing its high speed to the northwest, supposing that the comet would complete an entire revolution of the sky in a short time. But Cassini, in his memoirs, remembers having to explain to her that the comet movement had to appear to slow down and become stationary.

“She was very surprised, and after further requests for explanations, he exposed in more detail his work and asked her permission to dedicate it to her. This work was published in May 1665, in Rome, with the Latin title Theoria motus cometae anni MDCLXIV [i.e., II]. It collected the observational data of both the 1664 and the 1665 comets – the former from 18 December to 15 January, the latter dating to April of that year – and Cassini supposed that the latter was the same described by the Danish astronomer Tycho Brahe in 1577. As promised, his dedication reads ‘Christinae Alexandrae Suecorum Reginae Augustae’, the Queen Christine of Sweden, and also ends with: “Fulgeat interim diutissime Romano Coelo Maiestatis Tuae Sydus”, namely that the Queen’s star would long continue to shine in the Roman sky.

“This work is very important because it is the first that reports a precise sequence of observations and the entire path of a comet, also supported by mathematical calculations. Cassini, for the first time in history, tried to determine with the best possible accuracy the cometary movement, and, in this attempt, he employed the same laws used for the planets. The importance of this attempt should not be underestimated. It has to be remembered, in fact, that, according to the Aristotelean and Ptolemaic models, comets did not belong to the heavens, but they rather had a terrestrial origin. Tycho had already questioned this interpretation, with the comet of 1577, but the transition between the classical, geocentric, and Aristotelean physics and astronomy and the new heliocentric model, was still an ongoing process” (Bernardi, pp. 45-47).

“In a letter addressed to Prince Leopoldo de Medici, Ottavio Falconieri (1646-1676) wrote about the arguments Cassini was hoping to establish in this text. According to Falconieri, Cassini’s theory concerned with the motion of comets was aimed at demonstrating that they ‘did not move in a straight line perpendicular to the surface of the earth, but along the plane of the greatest circle [beyond the orbit of Saturn]’ around the sun, which is itself orbiting the stationary earth. More specifically, as he described in his published works on the topic [II & III], Cassini believed that the 1664 comet travelled in epicycles around the distant bright star Sirius. While that star orbits the earth. In other words, he believed the comet to be moving around the earth, not the sun, as Falconieri had intimated in his letter to Leopoldo. Additionally, he clearly denied that the rapid movement of the comet when in opposition to the sun could be used by Copernicans as proof of the mobility of the earth, since, according to Cassini, such motion could also be explained within a Tychonic geocentric system.

“Therefore, Cassini was proposing a theory that dismissed Galileo’s claim about the rectilinear path of comets emanating from vapours in the earth’s atmosphere. Furthermore, by placing the comet amongst the sphere of stars, Cassini was proposing a radical departure from most theories since the late sixteenth century on the location and movements of comets. Nevertheless, he still maintained a finite geocentric and geostatic model with circular motion, consistent with Tychonic astronomy” (Boschiero, pp. 223-224).

Cassini stated on several occasions “that although, when in opposition to the Sun, the comet could be used by Copernicans as proof of the mobility of the earth, such motion could also be explained within a Tychonic geometric system. [He reaffirmed that also in III, pp. 6-7]. Nevertheless, Cassini’s consistent public position during this period was that he could not accept the concept of a moving Earth. This public stance may well have been to appease ecclesiastical authorities in the Papal States, to which Bologna belonged, especially after the renewed Papal ban of Copernicanism in 1664” (Boschiero, ‘Giovanni Borelli and the Comets of 1664-1665,’ Journal for the History of Astronomy 40 (2009), p. 27).

“Like Cassini, Adrien Auzout (1622-91) approached astronomy using instruments rather than mathematics … After observing the comet of 1664 four or five times between December 22 and December 31, 1664, Auzout predicted cometary positions on the sky, an ephemeris, for dates from the previous November through February 1665 … Commenting on Cassini’s notion that the comet of 1664 moved in a circular orbit about Sirius, Auzout mentioned that he, too, thought of this idea and noted that the comet of 1651 had about the same speed as Sirius and came to perigee opposite the bright star. Auzout reasoned that if the comets of 1664 and 1651 were one, its reappearance could be expected around 1676. However, as he could find no recollection of a comet that appeared every 12 years and there was no evidence that well-observed comets arrive at perigee in conjunction with a notable star, Auzout could not endorse Cassini’s theory” (Yeomans, pp. 72-73).

“Auzout was much less sure than Cassini that the earth did not move. In fact, he had expressed the hope that the distance and magnitude of the comet could be determined, and that the question of the earth’s motion would thus be determined. He did not, however, accept the figures of Johann Hevelius, with their necessary consequences of a moving earth, which appeared shortly after … The Hevelius theory and figures were questioned because of his apparently erroneous observation of the comet on February 18, 1665” (Shapin, p. 226).

Cassini responded to the observations and theories of Auzout and Hevelius in two letters to Falconieri sent from Rome and dated 9 and 20 May, 1665 (i.e., III)

“In 1610, Galileo discovered with his telescope four Jupiter satellites, which he called Medicean stars. The great Pisan, sensing the great importance of an accurate determination of their motions for the problem of the longitudes entrusted his favorite pupil, Vincenzo Renieri, with the task of continuing his work on this subject. This monk, however, died suddenly in Genova in 1647 without having been able to produce the tables with the ephemerides of the Jovian satellites. Probably during his studies in Genova, Cassini, who mentions the name of Renieri in his biography, saw the sketches of the unfinished tables, but he also believed that, in order to finish this very important work, he needed time and, above all, suitable equipment” (Bernardi, p. 49).

“By 1664, … while Cassini was visiting Rome, he wrote that he had been invited by Campani ‘to come with him to Monte Citorio to observe Jupiter with a number of persons of distinction who were to meet there to test his telescopes. It was while making observations on that occasion that Cassini discovered the shadows of the satellites of Jupiter” (Bedini & Zanetti, p. 579). “Using the exact words of the astronomer: ‘While I was kept busy by the assignments of public character, I could make astronomical observations at night with an excellent telescope, which had been given to me by M. Campani, who had communicated to the public the discovery I had made of the shadows of the satellites of Jupiter onto the disc of this planet, which I had engaged other astronomers to observe’” (Bernardi, p. 52). These observations were published in IV, which contains three letters to Falconieri sent from Rome and dated 12, 20, and 26 October, 1665.

Cassini’s observations generated controversy partly because he had seen two kinds of spots on Jupiter: shadows of Jupiter’s moons and at least one spot that was physically on the surface of the planet. However, in June 166, “Huygens, who had been invited to the Observatory in Paris by Minister Jean-Baptiste Colbert, wrote to Prince Leopold, ‘As to what concerns the new observations made by Cassini on the shadows of the satellites of Jupiter, they appear to me to be excellent and fecund, and I have no doubt of his veracity, as I have learned there has been doubt from others, and even less after the same say, September 26^th of the year 1665, when I was able myself to observe clearly the shadow of the third satellite, which Cassini had predicted would appear’” (Bedini & Zanetti, p. 596).

The first observation of Jupiter’s Red Spot has sometimes been ascribed to Robert Hooke in 1664, but Falorni has shown that what Hooke observed was almost certainly the shadow of one of Jupiter’s moons. “As far as Cassini is concerned, it is beyond doubt that he repeatedly observed a spot quite like our modern Red Spot. It seems likely that his first observations were made at Cittá della Pieve, between the summer and the autumn of 1665; a full report was published the same year in the form of letters directed to the Abbot Falconieri [i.e., V]. Cassini’s interest in the spot concerned its use in determining the planet’s rotation period, which at the time was unproven …

“First he took care to single out – by means of computing – which spots were caused by the transit of a satellite or a satellite’s shadow on the planet’s disc. Secondly, Cassini demonstrated that the remaining observable spots had to be located on the true surface of the planet. Among these latter, he finally recognized a spot that was exceptionally conspicuous and permanent, and proved ideal for determining a highly reliable rotation period.

‘To that first light of distinction then followed the other of detecting among the number of the other spots a permanent one which was often seen to return in the same place with the same size and shape. It is the same spot that Yr. Ecc. was able to see just touching the real northern edge of that belt of Jupiter which, among the three obscurer ones, lies more southerly. That one, which among the spots hitherto observed is the greatest, the most conspicuous and the more permanent … appeared to be different in colour, not so dark and black [as the shadows], but quite like that of the obscure belts … different in figure as being, when nearer to the centre, larger in accordance with the line of the belt which it grazes, or narrower when nearer to the circumference” (V, p. 3).

“With these words Cassini described for the first time Jupiter’s Great Red Spot.

“On the basis of his own observations, which amounted to no less than 13 between August 19 and October 30, Cassini compiled a Table of the transits of the Spot [i.e., VI], from which he derived a rotation period of 9h 56m. His results were confirmed, on more than one occasion, by two groups of observers in Rome. The groups were headed by the well-known telescope makers and observers Campani and Divini, and Cassini had frequent contacts with them around that period. The fit between the computed and observed times of transit was excellent, and the Table confirmed that a previous observation on July 9 by Divini’s group – when a spot (‘semiumbram’) was seen to accompany the transit of the shadow of the third satellite – as also a Permanent Spot …

“Of all the Spot’s distinctive features, Cassini missed only its red colour, but it is out of the question that he would have been able to distinguish it because of the low light-grasp of telescopes of that time.

“The many observations that Cassini made in Paris from 1672 to 1694 – he had been appointed Director of the newly-built Royal Observatory – do not add anything of importance on the subject” (Falorni, p. 217).

“The discovery of the Jovian satellites [in III] was widely acclaimed, and it was described by a writer in the Journal des Sçavans in 1666 [p. 99] as being ‘one of the most wonderful that had yet been made in the sky’ and ‘one that required research to determine whether the phenomenon observed for the major planets was common as well to other components of the solar system.’ The writer of the journal added, ‘It should stimulate every researcher and observer to endeavour to perfect further the large telescopes until it is possible to discover whether or not other planets such as Mars, Venus, and Mercury, around which no satellites have been observed, do not come to an end or terminate revolving around their respective axes, and the amount of time required for it to take place, by Mars in particular, on which some spots have been observed.’

“This was a challenge to discovery that Cassini could not well overlook, and he was determined to find an answer. He decided he would begin with Mars. Thereupon at Bologna, during the months of February, March, and April 1666, he proceeded to make a new series of observations of the Red Planet. For this purpose, he used an excellent new telescope with which Campani had provided him. His studies of the spots that had appeared on the face of the planet and had been presented alternatively to his eye by the planet’s rotation were first described by Cassini in a public notice. The published table contained fine plates engraved from Cassini’s original drawing of Mars upon which the spots clearly appeared more or less dark, to which was given the characteristic aspect of the planet. Their displacement from east to west, until their disappearance, and the reappearance of the spots, with the same characteristics, provided a means to the astronomer for calculating the period of rotation of Mars, which he estimated to be 24 hours, 40 minutes … The published table bore the inscription, ‘The revolution of Mars upon its proper axis observed by J. D. Cassini at Bologna with a Campani telescope in the months of February, March, and April 1666’ [i.e., VII]” (Bedini & Zanetti, pp. 591-592).

Cassini’s “result would be contested by two Roman scientists who, using a Divini telescope, estimated a rotation period of 12 h… but Cassini’s work proved to be exact and the present day accepted rotation period of Mars is 23h 37min and 23s” (Bernardi, p. 56).

“Hearing of Cassini’s discoveries and work, King Louis XIV of France invited him to Paris in 1669 to join the recently formed Académie des Sciences. Cassini assumed the directorship of the Observatoire de Paris after it was completed in 1671, and two years later he became a French citizen.

“Continuing the studies begun in Italy, Cassini discovered the Saturnian satellites Iapetus (1671), Rhea (1672), Tethys (1684), and Dione (1684). He also discovered the flattening of Jupiter at its poles (a consequence of its rotation on its axis). In 1672, as part of a concerted effort to determine the size of the solar system more accurately, Cassini sent his colleague, Jean Richer, to South America so that roughly simultaneous measurements of the position of Mars could be made at Paris and Cayenne, French Guyana, leading to a better value for the Martian parallax and, indirectly, for the distance of the Sun. Between 1671 and 1679 Cassini made observations of the Moon, compiling a large map, which he presented to the Académie. In 1675 he discovered the Cassini Division and expressed the opinion that Saturn’s rings were swarms of tiny moonlets too small to be seen individually, an opinion that has been substantiated. In 1683, after a careful study of the zodiacal light, he concluded that it was of cosmic origin and not a meteorological phenomenon, as some proposed.

“In 1683 Cassini began the measurement of the arc of the meridian (longitude line) through Paris. From the results, he concluded that Earth is somewhat elongated (it is actually somewhat flattened at the poles). A traditionalist, he accepted the solar theory of Nicolaus Copernicus within limits, but he rejected the theory of Johannes Kepler that planets travel in ellipses and proposed that their paths were certain curved ovals, which came to be known as Cassinians, or ovals of Cassini. Although Cassini resisted new theories and ideas, his discoveries and observations unquestionably place him among the most important astronomers of the 17th and 18th centuries” (Britannica).

I. Lalande, Bibliographie astronomique (1803), p. 241; Riccardi, Biblioteca matematica italiana (1952), I.1, col. 275, no. 2. II. Lalande, p. 261; Riccardi, I.1, col. 276, no. 9. III. Lalande, p. 258; Riccardi I.1, col. 277, no. 14. IV. Lalande, p. 258; Riccardi I.1, col. 277, no. 13. V. Lalande, p. 258; Riccardi I.1, col. 277, no. 12. VI. Lalande, p. 258; Riccardi I.1, col. 277, no. 15. VII. Lalande, p. 266; Riccardi I.1, col. 278, no. 20. Bedini & Zanetti, Giuseppe Campani, “Inventor Romae,” an Uncommon Genius, 2021. Bernardi, Giovanni Domenico Cassini, 2017. Boschiero, Experiment and Natural Philosophy in Seventeenth-Century Tuscany, 2007. Falorni, ‘The discovery of the Great Red Spot of Jupiter,’ Journal of the British Astronomical Association, vol. 97 (1987), pp. 215-219. Shapin, ‘Early ideas about comets,’ Astronomical Society of the Pacific Leaflets 6 (1952), pp. 221-228. Yeomans, Comets. A Chronological History of Observation, Science, Myth, and Folklore, 1991.

Seven works in one volume, folio (318 x 214 mm). I. pp. [iv], 32, woodcut printer’s device on title. II. pp. [iv], 60 [i.e. 62], [2, index on recto, errata and colophon on verso], with one folding engraved plate, several tables and woodcut diagrams in text, decorative woodcut initials and tailpieces. III. pp. 22, [2], woodcut initials. IV. pp. 7, [1, blank], woodcut initial. V. pp. 12, decorative woodcut initials. The catchword at end of p. 12, ‘Illu-‘, may indicate that the work was originally meant to continue, but all copies have the same collation as ours. VI. pp. [4] (title page and 3 pages of tables). Some foxing and browning, mostly light but heavier on a few gatherings. VII. ff. [6], including two full-page engraved plates (versos blank). Occasional light browning, worm hole in blank margin of eight leaves. Later half-vellum with black lettering-piece on smooth spine (slight abrasion at the corners).

Item #5938

Price: $65,000.00