the death of Domitian to the accession of Commodus.” We need not stop to consider in this connection whether the decline of this prosperity caused the decay of self-government or was due to it. At all events the two processes were contemporaneous. To return from this brief account of city-life to the story of imperial politics,--as we have noticed, under the system which Augustus set up, there were two recognized sources of authority in the state, the prince and the senate. We say “recognized sources of power,” because in the background loomed up the sinister figure of the army, which was still capable of determining the fortunes of the state, as it had done in the times of Sulla and Marius, of Pompey and Caesar. Perhaps we may see the first step toward the intrusion of the army into politics again when Sejanus, the unscrupulous praetorian prefect of Tiberius, brought all the cohorts of the praetorian guard together in Rome. The control of these soldiers stationed in the capital put a powerful weapon in the hands of Sejanus, but, before he could strike, his designs were laid bare. The hereditary principle which Augustus had introduced, by adopting Tiberius and by conferring imperial honors upon him, a principle which was followed by his immediate successors, was for a time a safeguard for the succession. But when the Julian line became extinct on the murder of Nero, the field lay open to the imperial aspirant who was backed by the strongest army. After a year of struggle between four military leaders, Vespasian made good his claim to the prize, and in the year 69 founded a new dynasty, the Flavian. The precedent which Vespasian had set was not followed for a century, but from the close of the second century to the accession of Diocletian in 284 the praetorian guard and the army constituted the power which made and unmade the rulers of Rome. Within the period of seventy-three years which preceded the reign of Diocletian there were in fact twenty-three different emperors, almost all of whom owed their elevation to the throne to the force of arms, and kept their places on the throne so long as they could keep the favor of their armed supporters.