Same title, new contents.Saint-Venant’s revised edition (1864) of Navier'sRésumé des Leçons sur l'application de la mécanique (1826, 1833)

Following up some previous papers on Saint-Venant’s early unpublished studies of the years 1837-1853, on this occasion particular attention will be devoted to the improvement given by Saint-Venant to the third edition (1864) of Navier’s Résumé des leçons … sur l’application de la mécanique à l’établissement, first published in 1826 and reprinted in 1833 with few additions by Navier himself. Despite the great importance of Navier’s treatise, a comparison of his original textbook with Saint-Venant’s ‘revised’ edition shows the deep gap between the two works. This gap is of threefold nature: 1) methodological, in relation to Saint-Venant’s deductive approach starting from the general theory of elasticity; 2) theoretical, as far as concerns the correctness and generality of the derived formulae and their application to technical problems; 3) episthemological, in connection with Saint-Venant’s philosophical position in favour of the mécanique moléculaire and its disputed consequences on the number of elastic constants.