Anniversary Address of H. R. H. the late Presideiit. 65 



the obstacles ^vhich opposed his progress, the steady perseverance 

 with which he overcame them, and the courage with which he ven- 

 tured to expose the mystei'ious treasures of that sealed book, which 

 had hitherto only been approached by those whose way had been 

 cleared for them by a systematic and regular mathematical educa- 

 tion, Ave shall be fully justified in pronouncing him to have been a 

 most remarkable example of the pursuit of knowledge under diffi- 

 culties, and well worthy of the enthusiastic respect and admiration 

 of his countrymen, whose triumphs in the fields of practical science 

 have fully equalled, if not surpassed, the noblest works of the ancient 

 world. 



Pierre Louis Dulong was born at Paris in 1785: he became an 

 orphan at the age of four years ; and though hardly possessing the 

 most ordinary advantages of domestic instruction or public education, 

 his premature talents and industry gained him admission at the age 

 of 16 to the Polytechnic School, which has been so fertile in the pro- 

 duction of great men, of which he became afterwards successively ex- 

 aminer, professor, and director. He first followed the profession of 

 medicine, \vhich he abandoned on being appointed Professor of 

 Chemistry to the Faculty of Sciences. He became a member of the 

 Institute in 1823, in the Section of the physical sciences. On the 

 death of the elder Cuvier he was appointed Secretaire Perpetuel 

 to the Institute, a situation from which he was afterwards compelled 

 to retire by the pressure of those infirmities which terminated in 

 his death in the fifty-fourth year of his age. 



M. Dulong was almost equally distinguished for his profound 

 knowledge of chemistry and of physical philosophy. His " Re- 

 searches on the mutual decomposition of the soluble and insoluble 

 Salts," form a most important contribution to our knowledge of che- 

 mical statics. He was the discoverer of the hypophosphorous acid, 

 and also of the chlorure of azote, the most dangerous of chemical 

 compounds, and his experiments upon it were prosecuted with a 

 courage nearly allied to rashness, which twice exposed his life to 

 serious danger ; and his memoirs on the " Combinations of phospho- 

 rus with oxygen," on the " Jiyponitric acid," on the oxalic acid, 

 and other subjects, are sufficient to establish his character as a most 

 ingenious and accurate experimenter, and as a chemical philosopher 

 of th(! highest order. 



But it is to his researches on the " Law of the conduction of 

 heat," " On the specific heat of the gases," and " On the elastic 

 force! of steam at high temperatures," that his permanent fame as a 

 phih)SO])her will rest most securely : tiie first of these inquiries, wliich 

 were undertaken in conjunction with the late M. Petit, was publisiied 

 in 1817 ; aiul presents an admirable example of the combination of 

 well-dir(;ct(;d and most laborious and patient experiment with most sa- 

 gacious and careful induction : tiiese researches terminated, as is well 

 known, in tlit; very important cornu'tion of tiie ccilebrated law of 

 conduction, wiiicli Newton iuid announced in tiie Principia, and 

 wirutli Lapiacc!, Poisson, and Pourier iiad taken as tiie basis of their 

 beautiful matiiematical tiieorics of tin; pi'ojiagation of heat. Ilis ex- 

 Vhil. Mmj. S. 3. Vol. 14. No. 85. J(m. 1839. F 



