CLAUSEN, GEORGE (1852- ), English painter, was born in London, the son of a decorative artist. He attended the design classes at the South Kensington schools from 1867-1873 with great success. He then worked in the studio of Edwin Long, R.A., and subsequently in Paris under Bouguereau and Robert-Fleury. He became one of the foremost modern painters of landscape and of peasant life, influenced to a certain extent by the impressionists with whom he shared the view that light is the real subject of landscape art. His pictures excel in rendering the appearance of things under flecking outdoor sunlight, or in the shady shelter of a barn or stable. His “Girl at the Gate” was acquired for the nation by the Chantrey Trustees and is now at the National Gallery of British Art (Tate Gallery). He was elected associate of the Royal Academy in 1895, and as professor of painting gave a memorable series of lectures to the students of the schools,—published as Six Lectures on Painting (1904) and Aims and Ideals in Art (1906).
CLAUSEWITZ, KARL VON (1780-1831), Prussian general and military writer, was born at Burg, near Magdeburg, on the 1st of June 1780. His family, originally Polish, had settled in Germany at the end of the previous century. Entering the army in 1792, he first saw service in the Rhine campaigns of 1793-1794, receiving his commission at the siege of Mainz. On his return to garrison duty he set to work so zealously to remedy the defects in his education caused by his father’s poverty, that in 1801 he was admitted to the Berlin Academy for young officers, then directed by Scharnhorst. Scharnhorst, attracted by his pupil’s industry and force of character, paid special attention to his training, and profoundly influenced the development of his mind. In 1803, on Scharnhorst’s recommendation, Clausewitz was made “adjutant” (aide-de-camp) to Prince August, and he served in this capacity in the campaign of Jena (1806), being captured along with the prince by the French at Prenzlau. A prisoner in France and Switzerland for the next two years, he returned to Prussia in 1809; and for the next three years, as a departmental chief in the ministry of war, as a teacher in the military school, and as military instructor to the crown prince, he assisted Scharnhorst in the famous reorganization of the Prussian army. In 1810 he married the countess Marie von Brühl.
On the outbreak of the Russian war in 1812, Clausewitz, like many other Prussian officers, took service with his country’s nominal enemy. This step he justified in a memorial, published for the first time in the Leben Gneisenaus by Pertz (Berlin, 1869). At first adjutant to General Phull, who had himself been a Prussian officer, he served later under Pahlen at Witepsk and Smolensk, and from the final Russian position at Kaluga he was sent to the army of Wittgenstein. It was Clausewitz who negotiated the convention of Tauroggen, which separated the cause of Yorck’s Prussians from that of the French, and began the War of Liberation (see [Yorck Von Wartenburg]; also Blumenthal’s Die Konvention von Tauroggen, Berlin, 1901). As a Russian officer he superintended the formation of the Landwehr of east Prussia (see [Stein, Baron Vom]), and in the campaign of 1813 served as chief of staff to Count Wallmoden. He conducted the fight at Göhrde, and after the armistice, with Gneisenau’s permission, published an account of the campaign (Der Feldzug von 1813 bis zum Waffenstillstand, Leipzig, 1813). This work was long attributed to Gneisenau himself. After the peace of 1814 Clausewitz re-entered the Prussian service, and in the Waterloo campaign was present at Ligny and Wavre as General Thielmann’s chief of staff. This post he retained till 1818, when he was promoted major-general and appointed director of the Allgemeine Kriegsschule. Here he remained till in 1830 he was made chief of the 3rd Artillery Inspection at Breslau. Next year he became chief of staff to Field-marshal Gneisenau, who commanded an army of observation on the Polish frontier. After the dissolution of this army Clausewitz returned to his artillery duties; but on the 18th of November 1831 he died at Breslau of cholera, which had proved fatal to his chief also, and a little previously, to his old Russian commander Diebitsch on the other side of the frontier.
His collected works were edited and published by his widow, who was aided by some officers, personal friends of the general, in her task. Of the ten volumes of Hinterlassene Werke über Krieg und Kriegführung (Berlin, 1832-1837, later edition called Clausewitz’s Gesammte Werke, Berlin, 1874) the first three contain Clausewitz’s masterpiece, Vom Kriege, an exposition of the philosophy of war which is absolutely unrivalled. He produced no “system” of strategy, and his critics styled his work “negative” and asked “Qu’a-t-il fondé?” What he had “founded” was that modern strategy which, by its hold on the Prussian mind, carried the Prussian arms to victory in 1866 and 1870 over the “systematic” strategists Krismánic and Bazaine, and his philosophy of war became, not only in Germany but in many other countries, the essential basis of all serious study of the art of war. The English and French translations (Graham, On War, London, 1873; Neuens, La Guerre, Paris, 1849-1852; or Vatry, Théorie de la grande guerre, Paris, 1899), with the German original, place the work at the disposal of students of most nationalities. The remaining volumes deal with military history: vol. 4, the Italian campaign of 1796-97; vols. 5 and 6, the campaign of 1799 in Switzerland and Italy; vol. 7, the wars of 1812, 1813 to the armistice, and 1814; vol. 8, the Waterloo Campaign; vols. 9 and 10, papers on the campaigns of Gustavus Adolphus, Turenne, Luxemburg, Münnich, John Sobieski, Frederick the Great, Ferdinand of Brunswick, &c. He also wrote Über das Leben und den Charakter von Scharnhorst (printed in Ranke’s Historisch-politischer Zeitschrift, 1832). A manuscript on the catastrophe of 1806 long remained unpublished. It was used by v. Höpfner in his history of that war, and eventually published by the Great General Staff in 1888 (French translation, 1903). Letters from Clausewitz to his wife were published in Zeitschrift für preussische Landeskunde (1876). His name is borne by the 28th Field Artillery regiment of the German army.
See Schwartz, Leben des General von Clausewitz und der Frau Marie von Clausewitz (2 vols., Berlin, 1877); von Meerheimb, Karl von Clausewitz (Berlin, 1875), also Memoir in Allgemeine deutsche Biographie; Bernhardi, Leben des Generals von Clausewitz (10th Supplement, Militär. Wochenblatt, 1878).
CLAUSIUS, RUDOLF JULIUS EMMANUEL (1822-1888), German physicist, was born on the 2nd of January 1822 at Köslin, in Pomerania. After attending the Gymnasium at Stettin, he studied at Berlin University from 1840 to 1844. In 1848 he took his degree at Halle, and in 1850 was appointed professor of physics in the royal artillery and engineering school at Berlin. Late in the same year he delivered his inaugural lecture as Privatdocent in the university. In 1855 he became an ordinary professor at Zürich Polytechnic, accepting at the same time a professorship in the university of Zürich In 1867 he moved to Würzburg as professor of physics, and two years later was appointed to the same chair at Bonn, where he died on the 24th of August 1888. During the Franco-German War he was at the head of an ambulance corps composed of Bonn students, and received the Iron Cross for the services he rendered at Vionville and Gravelotte. The work of Clausius, who was a mathematical rather than an experimental physicist, was concerned with many of the most abstruse problems of molecular physics. By his restatement of Carnot’s principle he put the theory of heat on a truer and sounder basis, and he deserves the credit of having made thermodynamics a science; he enunciated the second law, in a paper contributed to the Berlin Academy in 1850, in the well-known form, “Heat cannot of itself pass from a colder to a hotter body.” His results he applied to an exhaustive development of the theory of the steam-engine, laying stress in particular on the conception of entropy. The kinetic theory of gases owes much to his labours, Clerk Maxwell calling him its principal founder. It was he who raised it, on the basis of the dynamical theory of heat, to the level of a theory, and he carried out many numerical determinations in connextion with it, e.g. of the mean free path of a molecule. To Clausius also was due an important advance in the theory of electrolysis, and he put forward the idea that molecules in electrolytes are continually interchanging atoms, the electric force not causing, but merely directing, the interchange. This view found little favour until 1887, when it was taken up by S.A. Arrhenius, who made it the basis of the theory of electrolytic dissociation. In addition to many scientific papers he wrote Die Potentialfunktion und das Potential, 1864, and Abhandlungen über die mechanische Wärmetheorie, 1864-1867.