triumphs of Aurelian, and carried his successful arms east, west, and north. Carus, despite his sixty years, crossed the Tigris and made good—at any rate in part—his threat to render Persia as naked of trees as his own bald head was bare of hairs. But Carus’s reign was brief, and at his death the Empire was divided between his two sons, Carinus and Numerian. The former was a voluptuary; the latter, a youth of retiring and scholarly disposition, quite unfitted for a soldier’s life, was soon slain by his Prætorian præfect, Arrius Aper. But the choice of the army fell upon Diocletian, and he, after stabbing to the heart the man who had cleared his way to the throne, gathered up into his strong hands the reins of power in the autumn of 284. He met in battle the army of Carinus at Margus, in Moesia, during the spring of 285. Carinus was slain by his officers and Diocletian reigned alone. ----- Footnote 3: Vopiscus, Florianus, c. 6. ----- But he soon found that he needed a colleague to halve with him the dangers and the responsibilities of empire. He, therefore, raised his lieutenant, Maximian, to the purple, with the title of Cæsar, and a twelvemonth later gave him the full name and honours of Augustus. There were thus two armies, two sets of court officials, and two palaces, but the edicts ran in the joint name of both Augusti. Then, when still further division seemed advisable, the principle of imperial partnership was extended, and it was decided that each Augustus should have a Cæsar attached to him. Galerius was promoted to be the Cæsar of Diocletian; Constantius to be the Cæsar of Maximian. Each married the daughter of his patron, and looked forward to becoming Augustus as soon as his superior should die. The plan was by no means perfect, but there was much to be said in its favour. An Emperor like Diocletian, the nominee of the eastern army alone and the son of a Dalmatian slave, had few, if any, claims upon the natural loyalty of his subjects. Himself a successful adventurer, he knew that other adventurers would rise to challenge his position, if they could find an army to back them. By entrusting Maximian with the sovereignty of the West, he forestalled Maximian’s almost certain rivalry, and the four great frontiers each required the presence of a powerful army and an able commander-in-chief. By having three colleagues, each of whom might hope in time to become the senior Augustus, Diocletian secured himself, so far as security was possible, against military rebellion.