[GALILEI, Galileo (156-1642) and] Benedetto CASTELLI (1578-1643).] Risposta alle opposizioni del S. Lodovico delle Colombe e del S. Vincenzio di Grazia, contro al Trattato del Sig Galileo Galilei. Florence, Cosimo Giunta, 1615.

First edition of Galileo’s principal work on the physics of floating bodies, complete with the additional leaf of errata and the colophon leaf. Like several of his polemics of his period, this treatise appeared under the name of a colleague, in this case his pupil and friend Castelli. It was written as a reply to two attacks by Colombe and Grazia on Galileo's 1612 treatises on floating bodies. "Using the concept of moment and the principle of virtual velocities, Galileo extended the scope of the Archimedean work beyond purely hydrostatic considerations" (DSB). Galileo's position involved philosophical principles, and was regarded as a challenge to the authority of Aristotle. In the present reply to his academic critics, he enlarged both the scientific reasoning behind his position and presented a vigorous philosophical defense of that position. It also contains a remarkable statement on page 62 to the effect that it is impossible to understand Copernicus without agreeing with him. This copy contains the rare two additional leaves (Y2) completing the errata and giving the registration and printer's device, not recorded by Cinti. Cinti 51 (without final errata leaf and register); Carli and Favaro 66; Riccardi I 289.

Quarto (206 x 148mm). Printer's device on title and colophon (a few old stains on p. 1, occasional toning, title and last leaf strengthened at inner margin). Contemporary vellum.