[GALILEI, Galileo (1564-1642)] and Mario GUIDUCCI (1585-1646). Discorso delle comete di Mario Guiducci. Florence: Pietro Cecconcelli, 1619.

First edition of Galileo's preliminary exposition on comets, the work which subsequently led to his composition of the celebrated Saggiatore. In 1618 the appearance of three comets had excited great interest throughout Europe. Comets were problematic phenomena at the time, since Aristotelian orthodoxy dictated that objects beyond the moon could not change shape or state. Among the many works written on these comets was one by the Jesuit mathematician Orazio Grassi. Galileo, suffering from ill-health, and perhaps cautious after his unsuccessful challenge to papal authority in 1616, dictated his views on comets to his pupil Guiducci, and the resulting work was published under Guiducci's name. Grassi is criticized but not named; as a result, however, he made Galileo the subject of a direct attack, published under the pseudonym of Lotario Sarsi. It was in response to this work that Galileo wrote Il Saggiatore. Carli-Favaro 17 (80); Cinti 137 (63); DSB V 242-3; Riccardi I 511.

Quarto (207 x 140mm). Woodcut device on title-page, headpieces and initials, 2 diagrams in text (first two leaves reinforced at gutter, some intermittent spotting/browning). Modern quarter morocco-backed boards.