CLAUSEWITZ. 4 the RliiiR- ill 17;i:i-94, and alteiulcd the Berlin Aeadcmy for young ollicers in 1801-03, when he attrai'te'd I he' attention and won the favor of Sohurnhorsl. lie «a.s adjutant to Prinee Auj;u.s- tus in i80(i, was eaptured with him by the Freneh at I'ri-iizhui, ami. after heiii;,' exelianf;ed, served until ISlii as major in the Prussian Uen- ural Stall', heing employed after ISOIt in the Min- istry of War, under Seharnhorst. In 1810-12 he was" also military instruetor to the Crown Prince of I'russia. and to I'riiiee Frederick of the Nether- lands. At the outhieak of the Russian War in 1812. he entered the Russian service, and aided Dieliitsch in concluding' the convention of Tau- roggen. lie accompanied BUicher as Russian stair ollieer duriny the campaign of 1813. the his- tory of which he wrote, at the instance of Gnei- sen'au. lie reentered the service of Prussia in 1814. was ai)pointed chief of staff under Thiel- mann in the follow'ing year, and remained in that position at Coblenz until 1818. when he was made major-general and director of the 'Allgemeiue Kriegsschule.' Finally, he was ap- pointed, in 1831, chief of staff to Field-ilar- shal Gneisenau, and served first in Berlin, then on the Polish frontier. His writings are of great value, and have led to a considerable change in the theory of war. Theywere published after his death as Hinlerlassene Werke iiher Erieg iiiiil Kric<ifiihruiifi (10 vols.. 1832-37). of which the most noteworthy are: T'ont Kriege; Der FeUlziig roii 179(1 in Itnlien; Uebersicht des Feld-:uges roit ISl.i; Dcr Feldzug von 1813; Veber diis Lebrn uuti den Charakter von Scharnhorst. CLATJSIXJS, klou'ze-us, Rudolf Julius Emaxuel (1S22-88). A German physicist, born at Kiislin. In 18.').5 he became professor in the Polytechnic Institute of Zurich, in 1867 pro- fessor in the University of Wtirzburg, and in 1869 professor at Bonn. Clausius is one of the founders of the modern science of themio- dynamics (q.v. ), and in a paper before the Ber- lin Academy of Sciences (1850) stated the sec- ond law of thermodynamics, that "heat cannot of itself pass from a colder to a hotter body." The theory of electrolysis advanced by Clausius has also played a consjjicuous part in electricity. He assumed that the ions are not in complete union, but that a part of them are free to unite with other ions. These uncombined ions, ac- cordingly, are brought together under the action of the current at the anode and cathode. Clau- sius was one of the most celebrated mathematical physicists of the nineteenth century, and his researches and writings in heat, electricity, and molecular physics of the greatest value. His most important works are: Die mechatiische Wdrmetheorie (1876); DiePotcntialfitnktionund dan Potential (1859); and Veber das Wesen der Warme, verglichen mit Licht und HeliuU (1857). For a biographv of Clausius. consult Riecke, Eudotf r'/i(».s;»,s(G;Utingen. 1889). CLAUSON-KAAS, klou'z6n-kas'. Adolf von (1826 — ). A Danish promoter of manual train- ing. He was born near Altona. of Danish parents, and after serving in the Danish cav- alry devoted himself entirely to the advance- ment of education. In 1870 he founded the Danish Clubs for Home Industry. On the oc- casion of the international expositions of 1873 and 1878. he gave a series of public lectures on manual tr.iining in several cities of Germany. Holland, Russia. France, and elsew-here. and also CLAVICHORD. fslablished a series of teachers" courses. In this way he encouraged the revival of working-schools lor boy.-., his primary aim being the mechanical developiiicnt ot the hand and of the eye in asso- ciation with mental training, lie conducted a number of training-seho(ds in Sa.ony. and intro- duced a course of modeling and drawing in the institution for the blind at Dresden. CLAUSTHAL, klous'liil (Ger., closed val- ley, from Lat. clausum, p.p. of cludere, to close -h Ger. Thai, valley). An impoilant mining town in the Prussian Province of Hanover, situated on a bleak plateau of the Upper Harz, about 1800 feet above sea-level, and 25 miles northeast of Gottingen (Map: Prussia. D 3). ^Jimong its public buildings the most noteworthy is the Churcli of the Hcly Ghost, built of wood in 1639, and considered the largest structure of its kind in the world. The mines of Clausthal yield silver, lead, copper, iron, and zinc, and are among the most valuable and jjroductive in (leriuany. They are owned and operated by the Prussian Government, which has established in connection therewith a mining academy, with an experimental laboratory, model workshop, and a library of over 30.000 volumes. The greater jjortion of the male population tinds employment in the mines and smelting-works. while the women are largely occupied in the knitting-mills. Population, in 1890. 8736: in 1900. 8565. Claus- thal was founded by the dukes of Brunswick, in the sixteenth century. CLAVA'RIA (Xeo-Lat. nom. pi., from Lat. claiHi, club). A genus of fungi of the division Hymenomycetes, subdivision Clavati. The spores are produced equally on all parts of the surface. The species are numerous, some of them simple and club-shaped, some branched. Clavaria botry- tis, a species common in oak and beech woods in Germany, growing on the ground among nios>, grass, heath, etc., is gathered when young, and used as food, having a very agreeable sweetish taste. It ceases to be edible when it becomes old. Another German species. Clavaria flava. which grows on sandy ground in fir-woods, is used in the same way. Other species appear to possess similar properties, and Liebig found them to contain the saccharine substance called mannite. Clavaria botrytis is the Keulenpilz, and Clavaria flava the Ziegenbart (goat's-beard) of the Germans. See Colored Plate of Edible FUXGI. CLAVERACK, klav'-er-ok. A town in Co- lumbia County, N. Y.. 30 miles south of Albany, on the Boston and Albany Railroad. The chief industries are agriculture and the manufacture of knit goods. The town has a jnildic library, and is the seat of the Hudson River Institute, established in 1854. Among the points of inter- est are a Dutch Reformed church, built in 1767. and an old court-house, erected in 1784. Settled as early as 1660. Claverack (named Klauver Rachen, 'clover reaches.' by the Dutch) was or- ganized as a town in 1788. and was the county- seat from 1780 to 1806. The government is ad- ministered by town meetings, held every two years. Population, in 1890, 4518; in 1900, 4416. CLA'VERHOUSE. See Graham, John. CLAVICHORD, klav'I-kord (Fr. clavicorde, Med. Lat. eJai irhordinui. from Lat. ctavis, key + chorda, string). An instrument of the harpsi- chord family, and an important step in the evo-
