THE THIRTY TYRANTS (A.D. 251-268).--Maximin was followed swiftly by Gordian, Philip, and Decius, and then came what is called the "Age of the Thirty Tyrants." The imperial sceptre being held by weak emperors, there sprang up in every part of the empire, competitors for the throne--several rivals frequently appearing in the field at the same time. The barbarians pressed upon all the frontiers, and thrust themselves into all the provinces. The empire seemed on the point of falling to pieces. [Footnote: It was during this period that the Emperor Valerian (A.D. 253-260), in a battle with the Persians before Edessa, in Mesopotamia, was defeated and taken prisoner by Sapor, the Persian king. A large rock tablet (see cut above), still to be seen near the Persian town of Shiraz, is believed to commemorate the triumph of Sapor over the unfortunate emperor.] But a fortunate succession of five good emperors--Claudius, Aurelian, Tacitus, Probus, and Carus (A.D. 268-284)--restored for a time the ancient boundaries, and again forced together into some sort of union the fragments of the shattered state. THE FALL OF PALMYRA.--The most noted of the usurpers of authority in the provinces during the period of anarchy of which we have spoken, was Odenatus, Prince of Palmyra, a city occupying an oasis in the midst of the Syrian Desert, midway between the Mediterranean and the Euphrates. In gratitude for the aid he had rendered the Romans against the Parthians, the Senate had bestowed upon him titles and honors. When the empire began to show signs of weakness and approaching dissolution, Odenatus conceived the ambitious project of erecting upon its ruins in the East a great Palmyrian kingdom. Upon his death, his wife, Zenobia, succeeded to his authority and to his ambitions. This famous princess claimed descent from Cleopatra, and it is certain that in the charms of personal beauty she was the rival of the Egyptian queen. Boldly assuming the title of "Queen of the East," she bade defiance to the emperor of Rome. Aurelian marched against her, defeated her armies, and carried her a captive to Italy (273 A.D.). After having been led in golden chains in the triumphal procession of Aurelian, the queen was given a beautiful villa in the vicinity of Tibur, where, surrounded by her children, she passed the remainder of her checkered life. The ruins of Palmyra are among the most interesting remains of Græco-Roman civilization in the East. REIGN OF DIOCLETIAN (A.D. 284-305).--The reign of Diocletian marks an important era in Roman history. Up to this time the imperial government had been more or less carefully concealed under the forms and names of the old republic. The government now became an unveiled and absolute monarchy. Diocletian's reforms, though radical, were salutary, and infused such fresh vitality into the frame of the dying state as to give it a new lease of life for another term of nearly two hundred years.