97 



is acquainted with the original must be aware of the great number 

 of steps in the demonstrations which are left unsupplied, in many 

 cases comprehending the entire processes which connect the enun- 

 ciation of the propositions with the conclusions, and the constant 

 reference which is made, both tacit and expressed, to results and 

 principles, both analytical and mechanical, which are co-extensive 

 with the entire range of known mathematical science : but in Dr. 

 Bowditch's very elaborate commentary every deficient step is sup- 

 plied, every suppressed demonstration is introduced, every reference 

 explained and illustrated, and a work which the labours of an ordi- 

 nary life could hardly master, is rendered accessible to every reader 

 who is acquainted with the principles of the differential and inte- 

 gral calculus, and in possession of even an elementary knowledge 

 of statical and dynamical principles. 



When we consider the circumstances of Dr. Bowditch's early life, 

 the obstacles which opposed his progress, the steady perseverance 

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

 tured to expose the mysterious 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, we shall be fully justified in pronouncing him to have been a 

 most remarkable example of the pursuit of knowledge under difli- 

 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 w^as 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- 

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

 medicine, which 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 " hyponitric acid,'' on the oxalic acid. 



