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Rh the revolutionary government, combined with the establishment of the bases of the decimal metrical system, gave employment and de- velopement to so many and such important scientific labours and discoveries : among many other laborious duties, the formation of the extensive tables devolved upon M. de Prony, who, in the course of two years, organized and instructed a numerous body of calcula- tors, and completed the immense Tables du Cadastre^ which are still preserved in MSS. at the library of the Observatory in seven- teen enormous folio volumes.

M. de Prony became Directeur-General des Ponts et Chaussees in 1794', and was nominated the first Professor of Mechanics to the Ecole Polytechnique ; — an appointment, which led to the publication of many very important memoirs on mechanical and hydraulical subjects, and on various problems of engineering, which appeared in the Journal of that celebrated school. He declined the invitation of Napoleon to become a member of the Institute of Egypt, — a re- fusal which was never entirely forgotten or pardoned. In the beginning of the present century he was engaged in the execution of very exten- sive works connected with the embankments towards the embouchure of the Po, and in the ports of Genoa, Ancona, Pola, Venice, and the Gulf of Spezzia; and in 1810, he was appointed, in conjunction with the celebrated Count Fossombroni of Florence, the head of the Com- missione de VAgro Romano, for the more effectual drainage and im- provement of the Pontine Marshes. The result of his labours in this very important task, which he prosecuted with extraordinary zeal and success, was embodied in his Description Hydrographique et Historique des Marais Pontins, which appeared in 1822, which contains a very detailed description of the past, present and pro- spective condition of these pestilential regions, and a very elaborate scientific discussion of the general principles which should guide us, in this and all similar cases, in effecting their permanent restoration to healthiness and fertility.

After the return of the Bourbons, M. de Prony continued to be employed in various important works, and more particularly in the formation of some extensive embankments towards the mouth of the Rhone. In 1817, he was made a member of the Bureait des Longi- tudes, and in the following year he was elected one of the fifty fo- reign members of the Royal Society: in 1828, he was created a Baron by Charles X., and was made a peer of France in 1835. He died in great tranquillity at Aonieres near Paris, in July last, in the 84th year of his age.

The Baron de Prony was a man of singularly pleasing manners, of very lively conversation, and of great evenness of temper. He was one of the most voluminous writers of his age, generally upon mathematical and other subjects connected with his professional pursuits; and though we should not be justified in placing him on the same level with some of the great men with whom he was associated for so many years of his life, yet he is one of those of whom his country may justly be proud, whether we consider the extent and character of his scientific attainments, or the great variety of important practical and useful labours in which his life was spent.