Note 636 — Chapter XXV

Je suis de l’opinion, says Descartes, de ceux qui disent que pondera sunt in æquilibrio quando sunt in ratione reciproca linearum perpendicularium, &c., vol. xi., p. 357. He would not name Roberval; one of those littlenesses which appear too frequently in his letters and in all his writings. Descartes in fact could not bear to think that another, even though not an enemy, had discovered anything. In the preceding page he says: C’est une chose ridicule que de vouloir employer la raison du levier dans la poulie, ce qui est, si j’ai bonne mémoire, une imagination de Guide Ubalde. Yet this imagination is demonstrated in all our elementary books on mechanics.