Figure 29.—Robert Willis (1800-1875), Jacksonian Professor, Cambridge University, and author of Principles of Mechanism, one of the landmark books in the development of kinematics of mechanisms. Photo courtesy Gonville and Caius College, Cambridge University.
Giuseppe Antonio Borgnis, an Italian "engineer and member of many academies" and professor of mechanics at the University of Pavia in Italy, in his monumental, nine-volume Traité complet de méchanique appliquée aux arts, caused a bifurcation of the structure built upon Hachette's foundation of classification when he introduced six orders of machine elements and subdivided these into classes and species. His six orders were récepteurs (receivers of motion from the prime mover), communicateurs, modificateurs (modifiers of velocity), supports (e.g., bearings), regulateurs (e.g., governors), and operateurs, which produced the final effect.[65]
[ [65] Giuseppe Antonio Borgnis, Théorie de la mécanique usuelle in Traité complet de mécanique appliquée aux arts, Paris, 1818, vol. 1, pp. xiv-xvi.
The brilliant Gaspard-Gustave de Coriolis (1792-1843)—remembered mainly for a paper of a dozen pages explaining the nature of the acceleration that bears his name[66]—was another graduate of the Ecole Polytechnique who wrote on the subject of machines. His book,[67] published in 1829, was provoked by his recognition that the designer of machines needed more knowledge than his undergraduate work at the Ecole Polytechnique was likely to give him. Although he embraced a part of Borgnis' approach, adopting récepteurs, communicateurs, and operateurs, Coriolis indicated by the title of his book that he was more concerned with forces than with relative displacements. However, the attractively simple three-element scheme of Coriolis became well fixed in French thinking.[68]
[ [66] Gaspard-Gustave de Coriolis, "Memoire sur les equations du mouvement relatif des systèmes de corps," Journal de l'Ecole Polytechnique, 1835, vol. 15, pp. 142-154.
[ [67] Gaspard-Gustave de Coriolis, De Calcul de l'effet des machines, Paris, 1829. In this book Coriolis proposed the now generally accepted equation, work = force × distance (pp. iii, 2).
[ [68] The renowned Jean Victor Poncelet lent weight to this scheme. (See Franz Reuleaux, Theoretische Kinematik: Grundzüge einer Theorie des Maschinenwesens, Braunschweig, 1875, translated by Alexander B. W. Kennedy as The Kinematics of Machinery: Outlines of a Theory of Machines, London, 1876, pp. 11, 487. I have used the Kennedy translation in the Reuleaux references throughout the present work.)
Michel Chasles (1793-1880), another graduate of the Ecole Polytechnique, contributed some incisive ideas in his papers on instant centers[69] published during the 1830's, but their tremendous importance in kinematic analysis was not recognized until much later.
[ [69] The instant center was probably first recognized by Jean Bernoulli (1667-1748) in his "De Centro Spontaneo Rotationis" (Johannis Bernoulli ... Opera Omnia ..., Lausanne, 1742, vol. 4, p. 265ff.).
