528 Royal Society. 



of the Cadastre, or gi-eat territorial and numerical survey of France, 

 — a gigantic undertaking, the subsequent execution of which, during 

 the revolutionaiy 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 tlie 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 Possombroni 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 extraoixlinary 

 zeal and success, was embodied in his Description Hydrographiqne 

 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 Bureau 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 

 l^aron 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 

 84'th 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 ma- 

 thematical and other subjects connected with his professional pur- 

 suits ; and though we should not be justified in placing him on 

 the same level with some of the great men with whom he was asso- 

 ciated for so many years of his life, yet he is one of those of whom 



