All this, we are to remember, went on without any furtherance of total domestic wealth-production. When corn-growing fell off, irrecoverably depressed by the unearned import from the richer soils of tributary provinces, there was a transference, partly economic, partly luxurious, of agricultural labour to vine-and olive-culture, and a wholesale turning of arable land to pasture. Some export of wine and olives followed, though the rich Romans tended to drink the wines of Greece. But Italy had ceased to be self-supporting. The produce she imported was far in excess of her power of export;[178] so that in sheer factitiousness the revenue of Rome is without parallel in history. Modern England, which has grown rich by burning up its coal in manufacture or selling it outright, but in the process has acquired a share in the national and municipal debts of all other countries--England is stable in comparison. While it lasts, the coal educes manufactures, which also earn imports and constitute loans. So with the recent exploitation of German iron; though in that case there has been much of sheer national waste in the wholesale export of iron at "dumping" prices in times of trade depression. But the history of Rome was a progressive paralysis of Italian production; and the one way in which the administration can be said to have counteracted the process--as apart from the spontaneous resort to vine-and olive-culture and to slave manufactures--was by forcing more-or-less unprofitable mining for gold and silver wherever any could be got, thus giving what stimulus can be given to demand by the mere placing of fresh bullion on the market. Roman civilisation was thus irrevocably directed to an illusory end, with inevitably fatal results. Bullion had come to standfor public wealth, and wars were made for mines as well as for tribute, Spain in particular being prized for her mining resources. As a necessary sequence, therefore, copper money was ousted by silver (B.C. 269), and silver finally, after a long transition period, by gold, about the time of Severus.[179] The silver had been repeatedly debased when the treasury was in difficulties;[180] and in the later days of the Empire it seems to have been base beyond all historic parallel,[181] though a large revenue was extorted till the end. Between revenue and tax-farming profits and the yield of the mines, the Roman moneyed class must indeed have spent a good deal, so long as the tributaries were not exhausted. But their economic demand was mainly for--(_a_) foods, spices, wines, cloths, gems, marbles, and wares produced by the more prosperous provinces; (_b_) expensive forms of food, fish, and fowl, raised chiefly on the estates run by their own class; (_c_) some wares of home production; and (_d_) _services_[182] from artists, architects, master craftsmen, slaves, mimes, parasites, and meretrices, whose economic demand in turn would as far as possible go in the same directions.