To connect the Rhine and Danube at their sources by a massive wall, to establish forts with strong garrisons at every point where these rivers could be easily forded, such were the precautions by which wise Emperors planned to shut in Rome’s civilization, and to keep out all who would lay violent hands upon it. The Emperor Augustus left a warning to his successors that they should be content with these natural boundaries, lest in pushing forward to increase their territory they should in reality weaken their position. It is easy to agree with his views centuries afterwards, when we know that the defences of the Empire, pushed ever forward, snapped at the finish like an elastic band; but the average Roman of imperial days believed his nation equal to any strain. It was a boast of the army that ‘Roman banners never retreat’. If then a tribe of barbarians were to succeed in fording the Danube and in surprising some outpost fort, the legions sent to punish them would clamour not merely to exact vengeance and return home, but to conquer and add the territory to the Empire. In the case of swamps or forest land the clamour might be checked; but where there was pasturage or good agricultural soil, it would be almost irresistible. Emigrants from crowded Italy would demand leave to form a colony, traders would hasten in their footsteps, and soon another responsibility of land and lives, perhaps with no natural protection of river, sea, or mountains, would be added to Rome’s burden of government. Such was the fertile province of Dacia, north of the Danube, a notable gain in territory, but yet a future source of weakness. [Sidenote: Government of the Roman Empire] At the head of the Empire stood the Emperor, ‘Caesar Augustus’, the commander-in-chief of the army, the supreme authority in the state, the fountain of justice, a god before whose altar every loyal Roman must burn incense and bow the knee in reverence. It was a great change from the old days, when Rome was a republic, and her Senate, or council of leading citizens, had been responsible to the rest of the people for their good or bad government. The historian Tacitus, looking back from imperial days with a sigh of regret, says that in that happy age man could speak what was in his mind without fear of his neighbours, and draws the contrast with his own time when the Emperor’s spies wormed their way into house and tavern, paid to betray those about them to prison or death for some chance word or incautious action. Yet Rome by her conquests had brought on herself the tyranny of the Empire.