Something similar happened to the gold. The aureus, though it kept its fineness, lost in weight down to Constantine. In the reign of Augustus it equalled one-fortieth of a Roman pound of gold, in that of Nero one forty-fifth, in that of Caracalla but one-fiftieth, in that of Diocletian one-sixtieth, and in that of Constantine one seventy-second, when the coin ceased passing by tale and was taken only by weight.[39]
The repudiation of the denarius was an act of bankruptcy; nor did the financial position improve while the administration remained at Rome. Therefore the inference is that, toward the middle of the third century, Italy had lost the treasure she had won in war, which had gradually gravitated to the centre of exchanges. This inference is confirmed by history. The movements of Diocletian seem to demonstrate that after 250 A.D. Rome ceased to be either the political or commercial capital of the world.
Unquestionably Diocletian must have lived a life of intense activity at the focus of affairs, to have raised himself from slavery to the purple at thirty-nine; and yet Gibbon thought he did not even visit Rome until he went thither to celebrate his triumph, after he had been twenty years upon the throne. He never seemed anxious about the temper of the city. When proclaimed emperor he ignored Italy and established himself at Nicomedia on the Propontis, where he lived until he abdicated in 305. His personal preferences evidently did not influence him, since his successors imitated his policy; and everything points to the conclusion that he, and those who followed him, only yielded to the same resistless force which fixed the economic capital of the world upon the Bosphorus. In the case of Constantine the operation of this force was conspicuous, for it was not only powerful enough to overcome the habit of a lifetime, but to cause him to undertake the gigantic task of building Constantinople.
Constantine was proclaimed in Britain in 306, when only thirty-two. Six years later he defeated Maxentius, and then governed the West alone until his war with Licinius, whom he captured in 323 and afterward put to death. Thus, at fifty, he returned to the East, after an absence of nearly twenty years, and his first act was to choose Byzantium as his capital, a city nearly opposite Nicomedia.