Item #5615 De motu impresso a motore translato. Epistolae duae. Pierre GASSENDI.
De motu impresso a motore translato. Epistolae duae.
“The First Precise Published Formulation of the Principle of Inertia” (H. Jones)
Paris, Ludovicus de Hequeville, 1642.

De motu impresso a motore translato. Epistolae duae.

4to [21.6 x 17.0 cm], (4) ff., 159 (i.e. 151) pp., with woodcut device on title, woodcut diagrams, woodcut headpieces and initials. Bound in contemporary vellum, red sprinkled edges. Minor rubbing and handsoiling to covers, annotations on endpapers. Cancelled manuscript shelf mark on title, early annotations in several hands, small corner loss at p. 59.

Rare first edition of Pierre Gassendi’s (1592-1655) important illustrated treatise on inertial mechanics. Written in the form of two letters addressed to the scholar and keeper of the king’s library Pierre Depuy (1582-1651), the De motu impresso “contains the first precise published formulation of the principle of inertia” as recently advanced by Galileo (Jones, p. 63). “Gassendi had taken up Galileo’s research almost as soon as it had been published in the Two New Sciences in 1638. He made experiments with inclined planes and dropped stones from the mast of a moving ship and confirmed Galileo’s results and predictions. On paper, he studied Galileo’s unaccelerated and unretarded uniform horizontal motion in an imaginary space outside the world and succeeded in abstracting the first statement of the principle of inertia from both the intrinsic gravity and circular motion that had enthralled Galileo” (Hooper, pp. 149-50).

“On one point – and it is an important one – [Gassendi] was more successful than Galileo: he correctly stated the principle of inertia. The experiment of the De motu impresso a motore translato, performed in 1640 in Marseilles, overthrew the argument of Copernicus’s opponents against the movement of the earth. Gassendi arranged to have a weight dropped from the top of a vertical mast on a moving ship in order to demonstrate that it fell at the foot of the mast and not behind it, thus sharing in its fall the forward motion of the ship. Gassendi understood that the composition of motions is a universal phenomenon. Motion is, in itself, a physical state, a measurable quantity, not – as the Scholastics maintained – the change from one state to another. It changes only through the interposition of another movement or of an obstacle” (DSB, vols. 5 & 6, p. 288).

“In this regard, Gassendi was able to take a step beyond Galileo’s conclusions, drawing from this test a generalized principle of inertia (the Galilean version of inertia was fundamentally circular, given that bodies in motion would trace the earth’s curve). Gassendi saw that the motion of the dropped stone at a sustained speed – in the absence of any contrary force or obstacle – is an instance of inertial motion, albeit one where the motion is compositional (describing the parabola). Indeed, neither compositionality nor directionality had any impact on inertial motion, Gassendi concluded: any body set in motion in any direction continues, unless impeded, in a rectilinear path” (See, Fisher).

The De motu impresso is also notable for its diagrammatic representations of the mathematic of motion, namely in its abandonment of Galileo’s ‘triangle of speeds’ in favor of “a visually and conceptually different representation based on a lattice of triangles” (Meli, p. 120, and see, Palmerino, passim).

OCLC locates U.S. copies at Harvard, Oklahoma, Smithsonian, and New York Soc. Library.

* W. Hooper, “Inertial Problems in Galileo’s Preinertial Framework,” in The Cambridge Companion to Galileo, P. Machamer, ed., pp. 146-74; S. Fisher, “Pierre Gassendi,” The Stanford Encyclopedia of Philosophy; D. B. Meli, Thinking with Objects: The Transformation of Mechanics in the Seventeenth Century, pp. 120-1 and 145-6; H. Jones, Pierre Gassendi, 1592-1655: An Intellectual Biography; C. R. Palmerino, “The Geometrization of Motion: Galileo’s Triangle of Speed and its Various Transformations,” Early Science and Medicine, vol. 15, nos. 4/5 (2010), pp. 410-47.


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