Biographical sketches Baudouin de Gu`emadeuc, Armand Henri (1734–1817) Baudouin worked as a civil servant in Paris, but little is known of his life except that he had an interest in both astronomy and literary culture. At one time he was imprisoned for fifteen months, and later he was forced to leave France. In 1782 he published in Neuchˆatel, Switzerland, a collection of anecdotes entitled L’Espion d´evalis´e. The book appeared anonymously and was for a long time ascribed Honor´e Mirabaud. In the spring of 1761 he looked in vain for the satellite of Venus, after which he established contact with Montaigne and requested that he proceeded in the hunt. After Montaigne’s success, Baudouin read two papers on the Venus moon to the Academy in Paris. His published version, M´emoire sur la d´ecouverte du satellite de V´enus, appeared in 1761 and was translated into German and English. Confident that the elusive satellite had now been discovered, he used Montaigne’s observations to determine the mass of Venus, which he stated was almost the same as the mass of he Earth. He also predicted the appearance of the satellite on the day of the transit. In company with Messier, he observed the transit on 6 June 1761, but saw no moon. In 1768 Baudouin made observations of Venus and the satellites of Jupiter, which he communicated to the Acad´emie des Sciences. After that time, he seems to have disappeared from the scene of astronomy. Bianchini, Francesco (1662–1729) During most of his career, Bianchini served the Catholic church. He wrote a world history (Istoria universale) and spent great efforts to improve the accuracy of the calendar. In 1703 he was elected secretary for the commission for the reform of the calendar. As a papal envoy and esteemed scholar, in 1712 he was sent to France and England, where he was received with great respect. In Paris he met with the aging Cassini, and in London he was welcomed by Newton with whom he had several conversations. His best known astronomical work, entitled Hesperi et phosphori, 156 Biographical sketches was published in Rome in 1728. In this first monograph about Venus, he studied the elusive markings of the planet and determined its rotation period to 24 days 8 hours. He drew a map of Venus and suggested names for several “oceans” and “continents.” Craters on Mars and Venus are now named in Bianchini’s honour. Although he did not see, nor believe in, the Venus moon, nor did he believe that the observations of Fontana and Cassini were caused by optical illusions. As an alternative he suggested that they were due to a fluid substance in interplanetary space. Bonnet, Charles (1720–1793) Born in Geneva, he spent his entire life in Switzerland as an independent naturalist and author. Within natural history, he made several important discoveries, in par- ticular that certain tiny insects could reproduce by means of parthenogenesis. He was in favour of preformation, the view that every creature existed in a preformed state within the egg, and in palaeontology he supported the philosophy of catas- trophism. A great advocate of the principle of plenitude, he expounded this idea in his popular Contemplation de la nature of 1764. The work dealt briefly with the planetary system and included comments on the satellite of Venus, which Bonnet thought might well exist. There is another connection to astronomy, namely by way of the German translation made by Johann Daniel Titius in 1766. Titius in- serted his own speculation concerning the distances of the planets, the first version of what came to be known as the Titius-Bode law. Possibly inspired by Bonnet, the Dutch minister and writer J. F. Martinet discussed the satellite of Venus in his Katechismus der Natuur of 1779. Boscovich, Roger Joseph (1711–1787) Rudjer Josip Boˇskovi´c, as his name is also spelled, was born in Ragusa (now Dubrovnik) in Croatia. He entered the Jesuit order in 1725 and began studies at the Collegio Romano in Rome, where he was made a professor of mathematics in 1740. He later became a professor in Pavia and helped (with Louis Lagrange) to establish the observatory in Brera. Throughout his career, he travelled widely and was very well connected. As a correspondent for the Royal Society, he was involved in the preparations to observe the Venus transits of 1761 and 1769. Boscovich is today best known for his dynamical theory of matter, an atomic theory based solely on a universal law of force, which he developed in his Theoria philosophiae naturalis of 1758. He also did important work in astronomy and optics, in particular in the theory of telescopes and other optical instruments. Much of this work was collected in a book of 1767, Dissertationes quinque ad dioptricam, which included a section on secondary images and the apparent satellite of Venus. Boscovich did not believe Biographical sketches 157 in the satellite and explained the observations as optical illusions, much in the same way that his fellow Jesuit Maximilian Hell had done the previous year. Strangely, he did not refer to Hell’s investigation. Cassini, Jean Dominique (1625–1712) The scientific career of Gian or Giovanni Domenico Cassini, as his Italian name was, began in Bologna, where he studied under Riccioli and Grimaldi. Through patronage connections, in 1650 he was appointed professor of astronomy at the University of Bologna, where he stayed for nearly twenty years. In 1669, he became amemberoftheAcad´emie Royale des Sciences and was recruited as the first di- rector of the new observatory in Paris. He became naturalized as a French citizen in 1673. During his period in Bologna, Cassini made a series of important obser- vations, which included the rotation periods of Mars and Jupiter. He also came up with a rotation period of Venus a little less than 24 hours. In 1668 he pub- lished new tables of Jupiter’s satellites, the Ephemerides Bononsienses Mediceo- rum Syderum. In Paris, working with telescopes constructed by Campani, he found two new moons of Saturn in 1671–72 and another two moons in 1684. In 1675 he observed the gap in Saturn’s ring system known today as the Cassini division. He was also a pioneer in the study of the zodiacal light, which he thought was of cosmic origin. In 1672 and again in 1686 he saw a faint object near Venus which had the appearance of a satellite, but he did not identify it as such. Although a brilliant observer, Cassini was conservative when it came to the- ory. He did not accept the determination of Ole Rømer of the velocity of light and opposed Newton’s theory of gravitation. Contrary to the Newtonians, he main- tained that the shape of the Earth was a prolate spheroid. During the last years of his life, he was blind. He was succeeded as director of the Paris Observatory by his son Jacques (1677–1756), and also his grandson C´esar-Fran¸cois (1714–1784) and his great-grandson Jean Dominique (1748–1848) became directors of the in- stitution. Dick, Thomas (1774–1857) Christian philosopher and high pluralist, the Irishman Thomas Dick was a suc- cessful author of popular and morally uplifting books on science. After studies at Edinburgh University, he was licensed to preach, but preferred instead a career as teacher and writer. His first work, The Christian Philosopher of 1817, employed natural theology and pluralism to emphasize the divine nature of the heavens. A later book, the Celestial Scenery of 1838, included a section on Venus’ moon in which Dick surveyed its history and suggested from reasons of analogy that the 158 Biographical sketches satellite was probably real. He also considered it probable that Mars might have a satellite. Fontana, Francesco (ca. 1585–1656) Known as a telescope maker and observational astronomer, Fontana graduated in law from the University of Naples, but he subsequently devoted himself to the construction of telescopes and other optical devices. He claimed to have built and used a telescope as early as 1608, before Galileo. Although appreciated as a tele- scope maker, his contemporaries did not hold him in high esteem as an astronomer. Among his many observations were the belts of Jupiter and the phases of Venus. He also observed the 1645 Mercury transit and made a number of drawings of the Moon. These he published in his only printed work, the Novae coelestium ter- restriumque observationes, which appeared in Naples in 1646. In this work he also reported markings on Venus and one or two small globes observed from Novem- ber 1645 to January 1646. Although he did not explicitly identify his discovery with satellites of Venus, most later astronomers thought he did. His discovery was mentioned by Riccioli, Gassendi and Kircher, none of whom believed in a Venus satellite. On the other hand, Guericke apparently supported Fontana’s claim. Hell, Maximilian (1720–1792) Born in Slovakia as the son of a Hungarian family, Hell’s original name was Miksa H¨oll. He entered the Jesuit order in 1738 and after studies of mathematics, as- tronomy and theology in Vienna he was ordained a priest in 1752. Three years later he was appointed professor of mechanics at the university and the follow- ing year the first director of its observatory. Among his many duties was to edit the Ephemerides astronomicae ad meridianem Vindobonensem published between 1757 and 1791. He was involved in the 1761 Venus transit project, and in connec- tion with the transit of 1769 he was invited by the king of Denmark to make measurements in Vardø in northern Norway.