a Syracusan, son of Hipparinus, famous for his power and abilities. He was related to Dionysius, and often advised him, together with the philosopher Plato, who at his request had come to reside at the tyrant's court, to lay aside the supreme power. His great popularity rendered him odious in the eyes of the tyrant, who banished him to Greece. There he collected a numerous force, and resolved to free his country from tyranny. This he easily effected on account of his uncommon popularity. He entered the port of Syracuse only in two ships; and in three days reduced under his power an empire which had already subsisted for 50 years, and which was guarded by 500 ships of war, and above 100,000 troops. The tyrant fled to Corinth, and Dion kept the power in his own hands, fearful of the aspiring ambition of some of the friends of Dionysius; but he was shamefully betrayed. Dion Cassius, a native of Nicaea in Bithynia. His father's name was Apronianus. He was raised to the greatest offices of state in the Roman empire by Pertinax, and his three successors. He was naturally fond of study, and he improved himself by unrestrained application. He was ten years in collecting materials for a history of Rome, which he made public in 80 books, after a laborious employment of 12 years in composing it. This valuable history began with the arrival of Aeneas in Italy, down to the reign of the emperor Alexander Severus. The 34 first books are totally lost, the 20 following, that is, from the 35th to the 54th, remain entire, the five following are mutilated, and fragments are all that we possess of the last 20. In the compilation of this extensive history, Dion professed to himself Thucydides as a model, but he is not perfectly happy in his imitation. His style is pure and elegant, and his narrations are judiciously managed, and his reflections learned; but upon the whole, he is credulous, and the bigotted slave of partiality, satire, and flattery. He inveighs against the republican principles of Brutus and Cicero, and extols the cause of Caesar. Seneca is the object of his satire, and he represents him as debauched and licentious in his morals.

Dionis, Peter, a distinguished French surgeon, was born in Paris. In the time of Louis XIV, he was appointed anatomical and surgical demonstrator in the royal garden, and he was the first who held that place. He was surgeon in ordinary to Maria Theresa of Austria, queen of France, and to two dauphinesses and the royal children. He was the author of several works, both on anatomical and surgical subjects. One of the first of his publications, is entitled Anatomie de l'Homme, suivant la Circulation du Sang, 8vo, which appeared in 1690, and has been frequently reprinted, and translated into different languages. It was translated into the Tartarian dialect by a Jesuit for the use of the emperor of China. This work has been considered as a useful compendium of anatomy. In another work which he published in 1698, entitled, Dissertation Historique et Physique sur la Generation de l'Homme, he supports the ovarian hypothesis. In 1707 he published a work on surgery, entitled Cours d'Operations de Chirurgie, 8vo, which was several times reprinted; and latterly it was edited with notes by La Faye in 2 vols. This treatise was long received as a standard book on the subject. It contains many useful and pertinent observations detailed in plain, unaffected language. Dionis is the author of two other works; the first, Sur la Mort subite, et sur la Catalepsie, published in 1709, and the other Traité generale des Accouchements, in 1718. But the last is little else than an abridgement of Mauriceau's work on the same subject. Dionis died at Paris in 1718.

Dionæa, Venus's fly-trap, a genus of plants belonging to the decandra class. See Botany Index.