PRONY, prone, Gaspard Clair Francois Marie Riche, BARON DE, French engineer: b. Chamelet, Rhone, 22 July 1755; d. Asnieres, Seine, 29 July 1839. He received his technical education at the Ecole des Ponts et Chaussees. As assistant to the civil engineer Perronet he was employed in building the bridge De la Con corde at Paris and the restoration of the harbor of Dunkirk. Made head of the board of sur vey, in 1791 he superintended the construction of new trigonometrical tables, extended to 25 decimal places, necessitated by the establishment of the metric system. This great work in 17 volumes is preserved in manuscript at the Ob servatory at Paris. In 1794 he was appointed director-general of bridges and roads and at the same time was made professor of mathematics at the Polytechnic School, in 1795 he becime a member of the Institute and in 1798 director of the Ecole des Ponts et Chaussies.
Under Napoleon he executed improvements in the harbor of Genoa, Ancona and Venice and in the navigation of the Po. In 1810 he became a member of the commission charged with the drainage and improvement of the Pontine Marshes. In 1818 he was made one of the 50 foreign members of the Royal Society and in 1835 a peer of France. He wrote several works of a technical character connected with the en gineering operations of which he had charge, the most important of which is 'Description Hydrographique et Historique des Marais Pontins' (2 vols., Paris 1822-23). He also published 'Nouvelle Architecture Hydraulique' (2 vols., Paris 1790-96) ; 'Viede (Paris 1796) ; Philosophique' (Paris 1800) ; de Mecanique (2 vols., Paris 1810-15).