Dec 21, 2020 Books of the Week — Elements d’Astronomie and Tables astronomique du Soleil, de la lune, des…

“We must believe then, that as from hence we see Saturn and Jupiter, if we were in either of the Two, we should discover a great many Worlds which we perceive not, and that the Universe extends so in infinitum.” — Cyrano de Bergerac 

Elements d’astronomie
Jacques Cassini (1677-1756)
Paris: De L’Imprimerie Royale, 1740
First edition
QB42 C3

Jacques Cassini succeeded his father as director of the Paris Observatory and continued his measurement of the meridian, a cartographic problem addressed by French Academicians beginning in 1669. In 1694, Cassini became a member of the Academy of Sciences and was admitted to the Royal Academy of Sciences in London in 1696. While there he met with John Flamsteed, Edmund Halley, and Isaac Newton. He never accepted Newton’s theory of gravity. Cassini’s own mathematical findings suggested, incorrectly, that the earth was elongated at the poles, contradicting Newton’s theory that the earth was flattened at its poles. He published his conclusions in 1720.

Cassini’s Elements d’Astronomie was the result of his excellent abilities as an observer. His principal areas of interest were the study of the planets and their satellites.  He also studied the comets and their influence on tidal behavior. In 1738, he discovered the proper motions of the stars. He showed, by direct measurement and for the first time, that the ancient belief in the unchanging sphere of the stars was incorrect. 

Cassini made impressive contributions to the field of astronomy with his study of the moons of Jupiter and Saturn and his study of Saturn’s rings. 

The Imprimerie Royale du Louvre was established in 1640 under Louis XIII and Cardinal Richelieu. Before this there had been “King’s Printers” who were entrusted with the typographical equipment belonging to the Crown, most importantly the “royal” types cut by Jean Jannon. In 1692, Louis XIV ordered that a new series of types be cut for the exclusive use of the Imprimerie Royale. A commission was appointed by the Academie des Sciences to design the new letters, and Philippe Grandjean became the royal typecutter. The result was the roman du roi, which took from 1693 to 1745 to complete, comprised of eighty-two complete fonts. The most obvious mark of the royal fonts is the small spur on the left side of the lower-case “l” mid-way up the stem. In this project, Grandjean was succeeded by his pupil, Jean Alexandre, who was in turn succeeded by Alexandre’s son-in-law, Louis Luce, all royal type-cutters.

Tables astronomiques du soleil, de la lune, des…
Jacques Cassini (1677-1756)
Paris : de L’Imprimerie Royale, 1740
First edition
QB12 C34

The tables in this book were so accurate that they were used by astronomers long after the book went out of print, although Edmund Halley noted many mistakes. Twenty-five copperplate engravings.