sans changer de place, witkout changing position

Page 141. — 1. longueur focale, focal distance or focal length, the distance from the center of the lens to the principal focus. 2. mouvement de translation, shifting.

Page 142. — 1. Descartes (1 596-1650), a very eminent philosopher and mathematician, and one of the greatest French prose writers of the seventeenth century. In addition to important scientific discoveries, his philosophical writings made him the founder of modem psychology.