*Renewal of the imperium.* His _imperium_, which lapsed in 18 B. C., Augustus caused to be reconferred upon himself for successive periods of five or ten years, thus preserving the continuity of his power until his death in 14 A. D. II. THE SENATE, THE EQUESTRIANS AND THE PLEBS *The three orders.* The social classification of the Romans into the senatorial, equestrian and plebeian orders passed, with sharper definitions, from the republic into the principate. For each class a distinct field of opportunity and public service was opened; for senators, the magistracies and the chief military posts; for the _equites_ a new career in the civil and military service of the princeps, and for the plebs service as privates and subaltern officers in the professional army. However, these orders were by no means closed castes; the way lay open to able and successful men for advancement from the lower to the higher grades, and for the consequent infusion of fresh vitality into the ranks of the latter. *The Senate and the senatorial order.* The senatorial order was composed of the members of the Senate and their families. Its distinctive emblem was the broad purple stripe worn on the toga. Sons of senators assumed this badge of the order by right of birth; equestrians, by grant of the princeps. However, of the former those who failed to qualify for the Senate were reduced to the rank of equestrians. The possession of property valued at 1,000,000 sesterces ($50,000) was made a requirement for admission to the Senate. The prospective senator was obliged to fill one of the minor city magistracies known as the board of twenty (_viginti-virate_), next to serve as a legionary tribune and then, at the age of twenty-five, to become a candidate for the quaestorship, which gave admission to the Senate. From the quaestorship the official career of the senator led through the regular magistracies, the aedileship or tribunate, and the praetorship, to the consulship. As an ex-praetor and ex-consul a senator might be appointed a promagistrate to govern a senatorial province; a legate to command a legion or administer an imperial province; or a curator in charge of some administrative commission in Rome or Italy.