The emperor Trajan rivaled Julius Caesar in military ability and enlarged the Roman world to the widest limits it was ever to attain. His first conquests were in Europe and resulted in the annexation of Dacia, an extensive territory north of the Danube. Thousands of colonists settled in Dacia and spread everywhere the language and arts of Rome. Its modern name (Rumania) bears witness to Rome's abiding influence there. Trajan's campaigns in Asia had less importance, though in appearance they were more splendid. He drove the Parthians from Armenia and conquered the Tigris- Euphrates valley. To hold in subjection such distant regions only increased the difficulty of guarding the frontiers. Trajan's successor, Hadrian, at once abandoned them. [Illustration: COLUMN OF TRAJAN A bronze statue of Trajan formerly occupying the top of the monument has been replaced by a figure of St Peter. The column is decorated with a continuous spiral relief representing scenes from the Dacian War. About twenty five hundred separate designs are included in this remarkable collection.] HADRIAN THE ADMINISTRATOR Hadrian distinguished himself as an administrator. He may be compared with Augustus in his love of peace and in his care for the interests of the provincials. Hadrian made two long journeys throughout the Roman world. On the frontiers he built fortresses and walls, in the provinces he raised baths, aqueducts, theaters, and temples. Scarcely a city throughout the empire lacked some monument to his generosity. Hadrian left behind him the memory of a prince whose life was devoted to the public welfare--the first servant of the state. [Illustration: WALL OF HADRIAN IN BRITAIN The wall extended between the Tyne and the Solway a distance of seventy miles. It was built of concrete faced with square blocks. The height is nearly twenty feet, the thickness about eight feet. Along the wall were numerous towers and gates and a little to the north of it stretched an earthen rampart protected by a deep ditch. A broad road, lined with seventeen military camps, ran between the two fortifications.] MARCUS AURELIUS, THE PHILOSOPHER ON THE THRONE The last of the "Good Emperors," Marcus Aurelius, was a thinker and a student, but he enjoyed little opportunity for meditation. His reign was filled with an almost uninterrupted series of campaigns against the Parthians on the Euphrates and the Germans on the Danube and the Rhine. These wars revealed the weakness of the frontiers and rapidly growing strength of the barbarians. After the death of Marcus Aurelius the empire entered on its downward course. But before passing to this period of our study, we may take a survey of the world under Roman rule, during the two centuries between Augustus and Marcus Aurelius. [Illustration: MARCUS AURELIUS IN HIS TRIUMPHAL CAR (Palace of the Conservatori, Rome) A panel from an arch erected by the emperor.] 69. THE PROVINCES OF THE ROMAN EMPIRE THE STANDING ARMY