Page:The Kinematics of Machinery.djvu/32

10 Bétancourt afterwards filled up the details in their "Essai sur la composition des machines" (1808). Monge had entitled the subject " ," which he intended to be equivalent to means for. He understood by these "means", and based on this idea the arrangement of mechanisms according to the possible combinations of four principal kinds of motion, viz.:, and. Omitting repetitions, these give ten classes of mechanisms, corresponding to the changes of motion between

This scheme,—or "system,"—was capable of extension,—and in the second edition (1819) it was extended by the addition of other fundamental motions,—continuous and reciprocating motions in curved lines,—increasing the number of classes from 10 to 21, but not altering the principle of classification. This indeed has remained with unimportant alterations in tolerably general use until the present time, and has thus acquired the sanction of very general recognition. Hâchette himself, who assisted in the production of Lanz' work, adopted it unconditionally in his, published in 1811. Borgnis, in his  (1818) departed from it to a certain extent; he considered the problem more generally than his predecessors, and divided the parts of machines into six classes, which he called, and   respectively.