BORELLI, Giovanni Alfonso (1608-1679). Risposta ... alle considerazioni fatte sopra alcuni luoghi del suo libro della forza della percossa del R. P. F. Stefano de gl’ Angeli ... all’illustrissimo ... Michel Angelo Ricci. [Messina: after 29 February, 1668.]

Unpressed, untrimmed copy of a rare work by Borelli on falling bodies. The present text is a response by Borelli to Stefano degli Angeli's criticisms of his 1667 De vi percussionis. It was published in the form of two letters to Michelangelo Ricci; there is no title-page, only the drop-title on A1, and no place of publication or printer given. The issue at the center of Angeli’s criticisms and Borelli’s response concerns the path of a falling body in relation to the movement of the earth, and the primary object of Angeli’s attack was actually the Jesuit astronomer Riccioli. The Jesuits had difficulty accepting the combination of different motions, which led to Riccioli concluding that the Earth did not move at all.

Borelli, in his 1667 treatise, had "argued that the trajectory of a body dropped from a tower in the hypothetical situation of a rotating Earth would be an irregular curve resulting from a uniform curvilinear motion acquired from the Earth’s rotation and a uniformly accelerated one. Borelli's position implied that the behavior of falling bodies differed depending on whether the Earth moved or not, thus making potential tests possible. At this point, Stefano degli Angeli entered the controversy against both Riccioli and Borelli" (Meli). Angeli was a Copernican who understood the Galilean relativity of motion and offered a serious critique of both authors. Borelli's response in the present work "introduced a novel element in the form of experiments designed to show that transverse velocity is conserved, an estimation of the order of magnitude of the eastward deviation, and a correction to his previous understanding of the body’s trajectory" (Ibid.). He developed here a significant theory of the eastward deviation of a falling body which would later be experimentally proved by G.G. Guglielmini in 1791. Carli and Favaro 311; Riccardi I 159.7. See Domenico Bertoloni Meli, Thinking with Objects. The Transformation of Mechanics in the Seventeenth Century (2006).

Quarto (231 x 173mm). 37pp. Woodcut illustrations in text (a little spotting at front). Later plain wrappers, uncut.