16 to 1 may be assumed as a rough average, although we frequently find cases of still greater depreciation of silver in Rome. The same movement beginning with the relative depreciation of gold and concluding with the fall in the value of silver, is repeated in the following epoch which has lasted from the Middle Ages to the present time. As in Xenophon’s times the average ratio in the Middle Ages was 10 to 1, changing to 16 or 15 to 1 in consequence of the discovery of the American mines. The discovery of the Australian, Californian and Columbian gold sources makes a new fall in the value of gold probable.115
C. THEORIES OF THE MEDIUM OF CIRCULATION AND OF MONEY.
As the universal thirst for gold prompted nations and princes in the sixteenth and seventeenth centuries, the period of infancy of modern bourgeois society, to crusades beyond the sea in search of the golden grail,116 the first interpreters of the modern world, the founders of the monetary system, of which the mercantile system is but a variation, proclaimed gold and silver, i. e. money, as the only thing that constitutes wealth. They were quite right when, from the