HUYGENS, Christiaan (1629-1695). Systema Saturnium, sive de causis mirandorum Saturni phaenomenon, et comite ejus planeta novo. The Hague: Adrian Vlacq, 1659.
4o (199 x 159 mm). One folding engraved plate, 11 engravings in text, 8 woodcut text diagrams, woodcut initials. Contemporary vellum (turn-ins slightly bowing).
FIRST EDITION OF THE FIRST FULL ANNOUNCEMENT OF HUYGENS' DISCOVERY OF THE RING AND SATELLITE OF SATURN. The mystery of Saturn's "arms" had puzzled astronomers in the decades following Galileo's observation in 1610 of the planet's oval shape. Starting in the 1650s, Huygens and his brother Constantijn acquired great skill in the grinding and polishing of spherical lenses, and the telescopes that they built were the best of their time. In 1655, using their first greatly improved telescope, Huygens spotted a satellite of Saturn, later named Titan. Although still unable to physically make out the cause of Saturn's odd and variable shape, Huygens theorized that it was due to a single flat ring, whose inclination to the line of sight varies. "He arrived at this solution partly through the use of better observational equipment, but also by an acute argument based on the use of the Cartesian vortex (the whirl of 'celestial matter' around a heavenly body supporting its satellites)" (DSB). In 1656 Huygens presented his theory in a one-sentence anagram included in Pierre Borel's De vero telescopii inventore, thus securing priority of the discovery. The Systema Saturnium contains as well "many other observations on the planets and their satellites, all contributing to an emphatic defense of the Copernican system", and an observation and illustration of the Orion nebula. Dibner Heralds of Science 9; Norman 1136.
HUYGENS, Christiaan. De circuli magnitudine inventa. Accedunt eiusdem problematum quorundam illustrium constructiones. Leiden: Elzevir, 1654.
4o. Engraved printer's device on title and diagrams in text.
FIRST EDITION of the author's rare second publication. "The importance of Huygen's mathematical work lies in his improvement of existing methods and his application of them in his improvement of existing methods and his application of them to a great range of problems in natural sciences In De circuli magnitudine inventa he approximated the center of gravity of a segment of a circle by the center of gravity of a segment of a parabola, and thus found an approximation of the quadrature; with this he was able to refine the inequalities between the area of the circle and those of the inscribed and circumscribed polygons used in the calculations of pi. The same approximation with segments of parabola, in the case of the hyperbola, yields a quick and simple method to calculate logarithms, a finding he explained before the Academy in 1666-67" (DSB). William 746.