And on one side only was such a sphere open to him. The East was Roman to the Euphrates. No second Mithridates could loosen the grasp with which the legions now held the civilized parts of Asia. Parthians might disturb the frontier, but could not seriously threaten the Eastern dominions; and no advantage was promised by following on the steps of Alexander and annexing countries too poor to bear the cost of their maintenance. To the west it was different. Beyond the Alps there was still a territory of unknown extent, stretching away to the undefined ocean, a territory peopled with warlike races, some of whom in ages long past had swept over Italy and taken Rome, and had left their descendants and their name in the northern province, which was now called Cisalpine Gaul. With these races the Romans had as yet no clear relations, and from them alone could any serious danger threaten the State. The Gauls had for some centuries ceased their wanderings, had settled down in fixed localities. They had built towns and bridges; they had cultivated the soil, and had become wealthy and partly civilized. With the tribes adjoining Provence the Romans had alliances more or less precarious, and had established a kind of protectorate over them. But even here the inhabitants were uneasy for their independence, and troubles were continually arising with them; while into these districts and into the rest of Gaul a fresh and stormy element was now being introduced. In earlier times the Gauls had been stronger than the Germans, and not only could they protect their own frontier, but they had formed settlements beyond the Rhine. These relations were being changed. The Gauls, as they grew in wealth, declined in vigor. The Germans, still roving and migratory, were throwing covetous eyes out of their forests on the fields and vineyards of their neighbors, and enormous numbers of them were crossing the Rhine and Danube, looking for new homes. How feeble a barrier either the Alps or the Gauls themselves might prove against such invaders had been but too recently experienced. Men who were of middle age at the time of Caesar's consulship could still remember the terrors which had been caused by the invasion of the Cimbri and Teutons. Marius had saved Italy then from destruction, as it were, by the hair of its head. The annihilation of those hordes had given Rome a passing respite. But fresh generations had grown up. Fresh multitudes were streaming out of the North. Germans in hundreds of thousands were again passing the Upper Rhine, rooting themselves in Burgundy, and coming in collision with tribes which Rome protected. There were uneasy movements among the Gauls themselves, whole nations of them breaking up from their homes and again adrift upon the world. Gaul and Germany were like a volcano giving signs of approaching eruption; and at any moment, and hardly with warning, another lava-stream might be pouring down into Venetia and Lombardy.