Du mouvement et de ses loix

Just added to our online edition of the Paris Manuscript of Du Châtelet’s Institutions de Physique is the important eleventh manuscript chapter, which focuses on motion and the laws of mechanics. You can read the transcriptions of the chapter and a full introduction here.

An excerpt from the introduction by Aaron Wells, on significant changes in the revisions of the manuscript:

One of many important revisions is to Du Châtelet’s Second Law of motion. In the fair copy version A, the law reads as follows: “Le changement qui arrive dans le mouvement d’un corps est toujours proportionnel a la force motrice qui en est la cause, et ce changement se fait toûjours dans la ligne droite dans laquelle cette force est dirigée” (208r). But in the final manuscript version G, the law instead reads: “Le changement qui arrive dans le mouvement d’un corps est toujours proportionnel à la force motrice qui agit sur lui; et il ne peut arriver aucun changemens dans la vitesse etla direction du corps en mouvement que par une force exterieure, car sans cela cechangement se feroit sans raison sufisante” (195r). Some notable differences in the latter version include (i) describing force as acting rather than as a cause; (ii) the deletion of any reference to direction of motion; (iii) the addition of a reference to an external force; and (iv) the addition of a reference to sufficient reasons for change. This version of the Second Law is kept, more or less unchanged, in the published versions.