kunde_ (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, _Militaer. Wochenblatt_, 1878).

CLAUSIUS, RUDOLF JULIUS EMMANUEL (1822-1888), German physicist, was born
on the 2nd of January 1822 at Koeslin, 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 Zuerich
Polytechnic, accepting at the same time a professorship in the
university of Zuerich In 1867 he moved to Wuerzburg 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 interchangin