This migration of capital, which caused the rise of Constantinople, was the true opening of the Middle Ages, for it occasioned the gradual decline of the rural population, and thus brought about the disintegration of the West. Victory carried wealth to Rome, and wealth manifested its power in a permanent police; as the attack in war gained upon the defence, and individual resistance became impossible, transportation grew cheap and safe, and human movement was accelerated. Then economic competition began, and intensified as centralization advanced, telling always in favour of the acutest intellect and the cheapest labour. Soon, exchanges became permanently unfavourable, a steady drain of bullion set in to the East, and, as the outflow depleted the treasure amassed at Rome by plunder, contraction began, and with contraction came that fall of prices which first ruined, then enslaved, and finally exterminated, the native rural population of Italy. In the time of Diocletian, the ancient silver currency had long been repudiated, and, in his well-known edict, he spoke of prices as having risen ninefold, when reckoned in the denarii of base metal; the purchasing power of pure gold and silver had, however, risen very considerably in all the western provinces. Nor was this all. It appears to be a natural law that when social development has reached a certain stage, and capital has accumulated sufficiently, the class which has had the capacity to absorb it shall try to enhance the value of their property by legislation. This is done most easily by reducing the quantity of the currency, which is a legal tender for the payment of debts. A currency obviously gains in power as it shrinks in volume, and the usurers of Constantinople intuitively condensed to the utmost that of the Empire. After the insolvency under Elagabalus, payments were exacted in gold by weight, and as it grew scarcer its value rose. Aurelian issued an edict limiting its use in the arts; and while there are abundant reasons for inferring that silver also gained in purchasing power, gold far outstripped it. Although no statistics remain by which to establish, with any exactness, the movement of silver in comparison with commodities, the ratio between the precious metals at different epochs is known, and gold appears to have doubled between Cæsar and Romulus Augustulus. 47 B.C. gold stood to silver as 1 : 8.9 1 A.D. under Augustus, “ “ “ 1 : 9.3 100–200, Trajan to Severus, “ “ “ 1 : 9–10 310, Constantine, “ “ “ 1 : 12.5 450, Theodosius II., “ “ “ 1 : 18