an elaborate and exhaustive
collection of his writings in twenty stout volumes, edited by MM.
Assezat and Tourneux, was completed in 1875-1877.

AUTHORITIES.--Studies on Diderot by Scherer (1880); by E. Faguet
(1890); by Sainte-Beuve in the _Causeries du lundi_; by F. Brunetiere
in the _Etudes critiques_, 2nd series, may be consulted. In English,
Diderot has been the subject of a biography by John Morley [Viscount
Morley of Blackburn] (1878). See also Karl Rosenkranz, _Diderots Leben
und Werke_ (1866). For a discussion of the authenticity of the
posthumous works of Diderot see R. Dominic in the _Revue des deux
mondes_ (October 15, 1902). (J. Mo.)

DIDIUS SALVIUS JULIANUS, MARCUS, Roman emperor for two months (March
28-June 2) during the year A.D. 193. He was the grandson of the famous
jurist Salvius Julianus (under Hadrian and the Antonines), and the son
of a distinguished general, who might have ascended the throne after the
death of Antoninus Pius, had not his loyalty to the ruling house
prevented him. Didius filled several civil and military offices with
distinguished success, but subsequently abandoned himself to
dissipation. On the death of Pertinax, the praetorian guards offered the
throne to the highest bidder. Flavius Sulpicianus, the father-in-law of
Pertinax and praefect of the city, had already made an offer; Didius,
urged on by the members of his family, his freedmen and parasites,
hurried to the praetorian camp to contend for the prize. He and
Sulpicianus bid against each other, and finally the throne was knocked
down to Didius. The senate and nobles professed their loyalty; but the
people made no attempt to conceal their indignation at this insult to
the state, and the armies of Britain, Syria and Illyricum broke out into
open revolt. Septimius Severus, the commander of the Pannonian legions,
was declared emperor and hastened by forced marches to Italy. Didius,
abandoned by the praetorians, was condemned and executed by order of the
senate, which at once acknowledged Severus.

AUTHORITIES.--Dio Cassius lxxiii. 11-17, who was actually in Rome at
the time; Aelius Spartianus, _Didius Julianus_; Julius Capitolinus,
_Pertinax_; Herodian ii.; Aurelius Victor, _De Caesaribus_, 19;
Zosimus i. 7; Gibbon, _Decline and Fall_, chap. 5.

DIDO, or ELISSA, the reputed founder of Carthage (q.v.), in Africa,
daughter of the Tyrian king Metten (Mutto, Methres, Belus), wife of
Ace