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DU GUESCLIN. 506 DUHRING. D tr G TI E S C Ii I N, (hi gu'klax', Bertrand (c.lj:i0-80). A Constable of France, the most celel>ralcd French soldier of his age. He was born at the Uastle of Motte-Broons, near Dinans, Briltany. and entered the service of Charles of Blois in 1342. In 1.3o4 he was knighted, and went with the lords of Brittany to England to secure the release of his captive master. He •rallantlv relieved Renncs, besieged by the Duke of Lancaster, in 135G, and by his help the city lield out until the truce of Bordeaux, in June. 1357. He soon took service under the French King, and after several brilliant actions was made Marshal of Normandy and Count of Longue- ville in 1304. At the battle of Auray, in 1304, he was taken prisoner, but was ransomed, and becoming commander of the Grand Companies (see CoNDOTTLEKE), led them into Spain, where he aided Henrv of Trastamare in his war against Pedro the Cruel. In 1367 he was taken prisoner by the Black Prince, then in alliance with Pedro the Cruel. Being again ransomed, he again fought for Henry, who received the kingdom in 1309. In 1370 he was made Constable of France, and for ten ears was active and successful in driving the English from the south and west of the country. In 1373 he seized and held most of the strongholds in the Duchy of Brittany. He died while besieging the fortress of Chateauneuf- Raudon. It is said that before his death the garrison had already promised to capitulate, and that their commander led them out and placed the keys of the castle upon the coffin of the Con- stable." Du Ouesclin was ugly in appearance, brutal in his manners, and uneducated; but he had great natural abilities, and profited by his long experience. Consult: Froissart, Chrunicles; Luce, Ilisloire de licrtrand du fliiesclin et de son ^poqvc (Paris. 1876) : Stoddard. Bertrand du ChicscUn, Constable of France (London, lSn7). DUHAMEL, du'a'mel', .Te. -1Iarie-Con- STANT (1797-1872). A French mathematician, born at Saint-italo. He occupied chairs in the Ecole Polytechnique. the Faculte des Sciences, and the Ecole Xormale Suix'rieure. Besides numerous memoirs on mathematics, he published the following works: Cours d'amil;/se (Paris, 1840-41): Elements de cajcul (1850-57; 4th ed. by Bertrand. 1887): Cowr.s de mccanique (184.")- 46) ; and Des methodes duns les sciences de rai- soiinement (5 vols.. 1806-72). "Duhamel exerted a great influence by the clearness and precision of his te;iching. Possessed of a mind more exact than profound, devoting himself especially to perfecting the methods by which science pro- gresses, he had the honor of being the first to give a rigorous demonstration of the principles upon which the infinitesimal calculus rests." ( Paul Tannery.) DUHAMEL, Joseph Thomas (1841—). A Canadian prelate. He was born in Contrecceur, studied at Saint .Joseph's College, Ottawa: was ordained in 1803, and became Bishop of Ottawa in 1874 and Archbishop in 1880. Through his efforts the college at Ottawa obtained the powers of a Catholic university. DUHAMEL DU MONCEAU, dii'il'mel' du moN'.u'. llEXRt Lotis 117(11181). A French botanist. He was born in Paris, and devoted himself to botany and arboriculture. He dis- covered that a disease of the saffron plant is caused by a parasitic fungus attacking the roots. In company with Buflon. and also independently, he exiierimented in vegetable and animal physi- ology. He was also interested in nautical mat- ters, and during the latter jiarl of his life was engaged as inspector-general of marine for the channel district of the French coast. On ac- count of his researches in arboriculture he was elected a member of the Academy of Sciences of Paris. His most important publication is Traitc des arbrcs et arbustcs, qui se cultivent en I'raiice en pleine tore (2 vols., Paris, 1755; 2d ed., known as Souicau Duhamel, cd. Etienne .Michel and others, 7 vols.. Paris, 1801-19). Other publications on arboriculture appearing between 1757 and 1783 were'7Vai7d des arbrcs fruilicrs and I'oiiioiki (lallica. DUHRING, dy'ring, Eugen Karl (1833—). A (.iernuiu jjliilosopher and political economist. He was born and educated in Berlin. After practicing law for three years he was compelled to abandon that profession in 1854 because of an all'eclion of the eye, which eventually resulted in blindness. He was lecturer on philoso])hy i,nd political economy at the Tniversity of Ber- lin from 18G4 until 1877. His philosophical standpoint is often called materialistic, but the epithet does not do justice to his views. He be- lieved in the competency of reason to compre- hend reality. Actual reality as it appears in our e.vperience is for him tlie only real existence and is thoroughly rational. He strenuously de- nies the Kantian doctrine that the categories (q.v.) of time and space Tiave only subjeetive validity. In ethics he is an opponent of egoism and pessimism. His writings, however, are full of bitter personalities. In 1877 he was deprived of the privilege of lecturing at the University of Berlin because of his violent attacks upon his colleagues in his works. His economic works frequently show the inlluencc of Henry C. Carey and other modern investigators. Among his most important publications are: Natiirliche Dinlehtil: (1805) ; Der Wert drs Lebeiis (5th ed. 1894) ; Kritische (lescliichte der Philosophic (4th ed. 1894) : Kritische Gcschichle der allpe- meinen Priiicipien der Mcchanik (3d ed. 1887), considered one of the best works on that subject : Kritische Geschichte der Xatioualol-oiiomic -und des Sozialismus (3d ed. 1879) : Die Judeufrupc nls Fraqe der liassenschiidlichUcit fiir Existeu:, fiiftcn vnd Kultur der VolKer (4th ed. 1892): Kursus der Philosophic (1875) ; Lonil: und TTis- seiischaftsthcorie (1878). Consult Diill, Eupcn Diihrinei: Etu-as von dessen Character, Leistun- ncn und rrformatorischem Bcruf (1893). DUHRING, doo'ring. Louis Adolphcs (1845 — I. Am American dermatologist, born in Phila- delphia, Pa. He graduated in the medical de- partment of the I'niversity of Pennsylvania in 1807, and in 1807-08 was a resident phvsieian of the Philadelphia Hospital. In 1808-70 he studied dermatology- in European hospitals, and in the latter year established in Philadelphia a dispensary for cutaneous diseases. He was ap- pointed clinical lecturer on dermatology at the University of Pennsylvania in 1871, and pro- fessor of diseases of the skin in 1870. His pub- lications include an Atlas of fihin Diseases (1870), and a Praelieal Treatise on Diseases of the fflcin (1878), the latter having been trans- lated into Italian, Russian, and French.