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Rh Vauquelin among the audience. They were so satisfied with what they had heard that they obtained for Thénard in 1797 an appointment as teacher of chemistry in a school, and in 1798 the post of repetiteur at the Ecole Polytechnique.

In 1804 Vauquelin resigned the professorship of chemistry at the College de France, and successfully used his influence to have Thénard appointed. In 1810 he succeeded Fourcroy both as professor of chemistry at the Ecole Polytechnique and as member of the Academy. He was also appointed professor of chemistry in the faculty of the sciences. He was made a chevalier of the Legion of Honour in 1814, commander in 1837, and grand officer in 1842. In 1825 Charles X. gave him the title of baron; from 1827 to 1830 he represented the department of Yonne in the chamber of deputies. In 1832 Louis Philippe made him a peer of France. As vice-president of the conseil superieure de l'instruction publique, he exercised a great influence on scientific education in France. He died 21st June 1857, and was buried at La Ferte, near Chalon-surSaone. In 1861 a statue was erected to him at Sens, and in 1865 the name of his native village was changed to La Louptiere-Thénard. The"nard was tall and strongly built, his hair was thick and black, his eyes bright, and his manner active and prompt. He married, in 1810, Mile. Humblot, granddaughter of Conte. His wife and several of his children predeceased him. He was survived by his son Paul, who had assisted him in some of his later researches.

Thénard was above all things a teacher: as he himself said, the professor, the assistants, the laboratory, every thing, must be sacrificed to the students. The history of his discovery of the peroxide of hydrogen well illustrates the predominance of the teacher in his character. He was lecturing on the formation of salts, and had told his students that a metal must be oxidized to a certain extent in order that it may combine with an acid to form a salt; if the metal be combined with more than the proper quantity of oxygen, the excess of oxygen will be given off when the oxide is treated with an acid, and, as an illus tration, he mentioned the action of acids on peroxide of barium. As he spoke his conscience smote him, for the experiment had not been made. Immediately after lecture he mixed peroxide of barium and nitric acid, keeping the temperature low by means of ice. He was surprised to see the peroxide dissolve without any evolution of gas. He left the mixture standing, and next day, before lecture, noticed small bubbles of gas rising from it. Pour ing some of the liquid into a test-tube and warming it, he saw a large amount of gas escape, which he easily recog nized as pure oxygen. At first he thought the acid had been oxidized, but he soon saw the true explanation of the phenomena, and discovered the peroxide of hydrogen. His lecture experiments were few, well-chosen, and accur ately performed. If any failure occurred he would roundly scold his assistant, often apologizing for his vehemence when the short fit of anger was over. His lecture room, seated for 1000, was almost always crowded by eager and attentive students and visitors.

Like most great teachers, Thénard published a text-book, and perhaps we may say that by his Traits de Chimie filementaire, Theorique et Pratique (4 vols., Paris, 1813-16; 6th ed., 5 vols., 1833-36) he did even more to further the progress of the science than by his numerous and important original discoveries. His first original paper (1799) was on the compounds of arsenic and antimony with oxygen and sulphur. Careful analyses led him to conclusions as to the composition of the metallic oxides contra dictory of some of Berthollet's theoretical views; he also showed (1802) that Berthollet's "zoonic acid" was impure acetic acid. Berthollet, far from resenting these corrections from a younger man, took this opportunity of introducing himself, and invited Thénard to become a member of the "Societe d Arcueil," to the proceedings of which Thénard contributed important papers. Soon after his appointment as repetiteur at the Ecole Polytechnique Thénard made the acquaintance of Gay-Lussac, and formed with him a lifelong friendship. Their joint work, and its relation to the discoveries of Davy, have been fully recorded in the article. Of his separate investigations perhaps the most important is that on the compound ethers, begun in 1807. He showed that each acid gives its own ether, and that the acid and alcohol can be recovered by decomposing the ether by means of caustic alkali. His discovery of peroxide of hydrogen (1818) has already been described. His researches on sebacic acid (1802) and on bile (1807) also deserve special notice. The blue substance known as Thénard's blue (essentially aluminate of cobalt) was prepared by him in response to a demand by Chaptal for a cheap blue, as bright as ultramarine, and capable of standing the temperature of the porcelain furnace.

Thénard's researches were chiefly published in the Annales de Chimie et de Physique, in tile Memoires dt la Societe d Arcueil, and in the Comptu Rendus and the Memoires of the Academy of Sciences.

 THEOBALD, (1688-1744), will survive as the prime butt of the original Dunciad when as a playwright, a litterateur, a translator, and even as a Shakespearean commentator, he will be entirely forgotten. The son of an attorney, Theobald was born at Sittingbourne, in Kent, in 1688, and, after a moderate education at Isleworth, studied for the profession of law,—a profession, however, which he never practised. He was a man with literary impulses, but without genius, even of a superficial kind; as a student, as a commentator, he might have led a happy and enviable life, had not the vanity of the literary idea led him into a false position. His Persian Princess (1711) and his Electra (1714) gained no distinction. In 1726 The Double Falsehood had a certain vogue, partly from Theobald's pretence that the greater part of the play was by Shakespeare. In 1717 he commenced a series of papers (uotnot [sic] to "The Censor," as has sometimes been stated, but under that title) which appeared in Mist's Weekly Journal; these do not seem to have been highly thought of by his contemporaries, but they were successful in gaining for Theobald not a few enemies, among whom Dennis may be named. Seven or eight years later Theobald's cen sorious tendencies had intensified rather than moderated, and in 1726 he ventured to attack the most eminent literary man of the day in his Shakespear Restored, or a Specimen of the many Errors as well committed as unamended by Mr Pope in his edition of this Poet. Two years later the censor was himself castigated severely, and, as the dedicatee of The Dunciad, he had long an unenviable notoriety; as readers of the famous satire will remember, he occupied the place of chief victim until replaced by Colley Gibber in 1743. In the matter of Shakespeare editing, however, he had the advantage of his powerful rival. When in 1733 Theobald published his edition of Shakespeare in seven volumes, that of Pope had to go to the wall. Lewis Theobald wrote other dramas besides those already men tioned, and translated plays from Sophocles and Aristo phanes, besides a rendering of Plato's Phxdo and a part translation of the Odyssey; but for none of these things is he now remembered. The student of English history might find it worth while to glance through Theobald's Life of Raleigh (1719). He died in 1744.

For plays, &c., see the Biographia Dramatica, vol. i.

 THEOCRITUS, of Syracuse, the foremost Greek pastoral poet, lived a life of which nothing is known except from allusions in his own works. The epigram appended to his poems makes him say, "I am a Syracusan, a man of the people, a son of Praxagoras and Philinna." He must have been born early in the 3d century, among a Dorian people, whose Dorian speech survives in his rural idyls. These "little pictures" chiefly represent the life of shepherds, neat-herds, and fishermen in the woods and on the shores of Sicily. They are doubtless inspired by the popular poetry of his time, and have much in common with the Romaic chants of the modern Greek shepherds. The first idyl is a song on Daphnis, the ideal