DESAULT
744
DESCARTES
tion won for him in 1853 the chair of physics at the
Sorbonne which he held for thirty-two years. His
lectures were characterized by great clearness and pre-
cision and many of his experimental illustrations were
devised or improved by him.
Between 1858 and 1861 he made many observations in connexion with terrestrial magnetism. His most important contributions to physics, however, were his researches on radiant heat made in conjunction with La Provostaye. With rare experimental skill the two physicists proved that radiant heat, like light, is a dis- turbance set up in the ether and propagated in all di- rections by transverse waves. They showed in a series of "M^moircs" published in the "Annales de Chimie et de Physique" that it manifests the characteris- tic phenomena of reflection, refraction, and polariza- tion, as well as of emission and absorption. They also made a study of the latent heat of fusion of ice, and a careful investigation of the range of applicability of the formula of Dulong and Petit representing the law of cooling. Of no less importance, however, was Desain's work in connexion with the establishment and development of laboratory instruction in physics. When the "Ecole pratique des hautes etudes" was founded in 1869 he was commissioned to organize the physical laboratory. He made it a model of its kind both in completeness and in convenience of detail. During the siege of Paris in 1870, he succeeded after many difficulties in establishing electrical communica- tion with d'Alm^ida who was outside the lines. The exposure he underwent brought on a rheumatism which greatly weakened his constitution. Desains published a "Traite de Physique" (Paris, 1855) and numerous articles, chiefly with La Provostaye. Among them are: "Recherches sur la chaleur latente de fusion de la glace" (Ann. de chim. et de phys. [3], VIII, 5); "Notes et m^moires sur les lois du rayonne- ment de la chaleur" (ibid., XII, 129, XVI, 337, XXII, 358); "M^moire sur la polarisation de la chaleur" (ibid, XXVII, 109, 232, XXVIII, 252, XXX, 159); "Memoire sur les anneaux colores" (ibid., XXVII, 423); "Memoire sur la reflexion de la chaleur" (ibid., XXX, 276); "Memoires sur la determination du pouvoir absorbant des corps pour la chaleur rayon- nante" (XXX, 431); etc.
Troost in Comptes-Rendus, ix, 1259; Mezieres, ibid,
H. M. Brock.
Desault, Pierre-Joseph, surgeon and anatomist, b. at Magny-Vernois a small town of Franche-Comtd, France, in 1744; d. 1 June, 1795. His parents were poor and he received his education from the Jesuits. He began his studies for the priesthood but gave this up for the study of medicine. His means not per- mitting him to go to a regular school of medicine he became an assistant to the barber-surgeon of his na- tive village and then took a similar post at the mili- tary hospital of Belfort. His favourite studies were anatomy and mathematics and he applied mathe- matical principles to his anatomical investigations. Borelli had done this with excellent results and De- sault translated Borelli's "De Motu Animalium" with notes and illustrations. He was not yet twenty when he went to Paris where, in 1766, after two years, he opened a school of anatomy. So practical and thor- ough were his methods of teaching that he soon had three hundred students, many of them older than himself. In order to protect himself from professional jealousy, as he had no degree, he opened his school under the name of a man already privileged to teach but whose name is not now known. Teaching brought him reputation but not much profit, and when in 1776 he was admitted to the Academy of Surgeons, he was allowed to pay his fees by instalments. In 1782 he became chief surgeon to the Charity Hospital and not long after surgeon to the Hotel-Dieu. He was now looked upon as the most prominent surgeon in Paris
and founded a school of clinical surgery which at-
tracted students from all sides. In 1793 he was im-
prisoned by the revolutionary authorities but after
three days was liberated through the influence of his
patients. He died from pneumonia, the result of ex-
posure whUe attending the Dauphin in the Temple.
He wrote a treatise on surgical operations in three
volumes ; a treatise on fractures and luxations, edited
by Xavier Bichat, was published after his death and
was translated into English in 1805 going through
three American editions. Desaiflt's contributions to
surgery are contained in the "Journal de Chirurgie"
published by himself and pupils.
Petit. Eloge de Desault (Lyons, 1795); Gderin, Disamrs in Bulletin de V Academie de medicine (Paris, 1876).
James J. Walsh.
Descartes, Rene (Ren.\t0s Cartesids), philos- opher and scientist, b. at La Haye, France, 31 March, 1596; d. at Stockliolm, Sweden, 11 Feb., 1650. He studied at the Jesuit college of La Fleche, one of the most famous schools of the time. In 1613 he went to Paris, where he formed a lasting friendship with Father Mersenne, O. F. M.. and made the acc|uaintance of the mathematician Mydorge. He afterwards enlisted in the armies of Maurice of Nassau, and of the Duke of Bavaria. On 10 November, 1619, he felt a strong impulse to set aside the prejudices of his childhood and of his environment, and to devote his life to the res- toration of human knowledge, which was then in a state of decadence ; and for him this mission took on quite a mystical character. He had a dream which he interpreted as a revelation, and he became convinced that "it was the Spirit of Truth that willed to open for him all the treasures of knowledge". After much journeying in Brittany, Poitou, Switzerland, and Italy, he returned to Paris in 1625. There he re- mained for two years during which it was his fortime ! • to meet Cardinal BeruUe who encouraged him in his scientific vocation. But as Paris offered neither the peace nor the independence his work demanded, he set out in 1629 for Holland, and there in the midst of a commercial people he enjoyed the advantage of li\ ihl; as quietly as in a desert. From this retreat he ga\i' to the world his "Discours de la methode" (lti:;7) "Meditations" (1641), "Principes" (1644), and " I'as sions"(1649). "Le Monde" had been completeii ii; 1633, but the condemnation of Galileo frightinr.: Descartes who preferred to avoid all collision \\itl ecclesiastical authoritj\ He deferred the publicatior,.,^ of this clever work without, however, losmg hope oijij.,, eventually bringing it out. In 1649, yielding to th<I|„ entreaties of Queen Christina, he went to Sweden, an(»-- died at Stockholm of inflammation of the lungs.
Descartes' work is important rather because nf it quality than of its quantity. Let us see first of al wherein his method is new. He observed, as Bacoii had already done before him, that there is no questioij on which men agree. "There is nothing", he saysj "so evident or so certain that it may not be contrC| verted. Whence then this widespread and deepi rooted anarchy? From the fact that our inquirif are haphazard " (Regies pour la direction de l'e.-;]iri 4® Regie). The first problem, then, is to discmt a scientific method. How is success in this ditliin task to be assured? To begin with, we must cease ( rely on authority; and for two principal reasons. '1 whom can we trust" when "there is hardly a stat ment made by one man, of which the opposite is w loudly supported by some other?" And even "if : were agreed, the knowledge of their teaching wou not suffice us." "Had we by rote all the argumen|| of Plato and Aristotle, we should not be any the mon philosophers unless we were able to bring to bear (| any given question a solid judgment of our own. Vj should have indeed learned history but not master;^ a science" (3 Regie). Philosophy presupposes tij
