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 enunciation 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 supplied, every suppressed demonstration is introduced, every reference explained and illustrated, and a work which the labours of an ordinary life could hardly master, is rendered accessible to every reader who is acquainted with the principles of the differential and integral 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 ventured 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 education, we shall be fully justified in pronouncing him to have been a most remarkable example of the pursuit of knowledge under difliculties, 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 production of great men, of which he became afterwards successively exminer, 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 " Researches on the mutual decomposition of the soluble and insoluble Salts," form a most important contribution to our knowledge of chemical 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 phosphorus with oxygen," on the "hyponitric acid," on the oxalic acid.
