The modern theory of international trade does not say that between two particular countries, or at any one particular point of time there is an equivalence of exchange, but that between a circle of commercially interconnected countries, and over a certain cycle of time or operations, there is an equivalence of exchange of goods and services. Movements of currency in the most elementary form assist the process, as far as immediate settlements are concerned; bills of exchange assist it when there is need of deferred payments, as, for instance, when a country imports steadily all the year round, but has only one export time, say after harvest; and, finally, bank and discount rates assist the process by providing currency media at times and places which would otherwise be unable to attract a supply. Over the whole circle of completed operations there is equilibrium of exchange, and the machinery by which that equilibrium is accomplished is currency in the widest sense. The index or indicator and safety-valve of the whole is the rate of interest. On these bank rates are based the operations of the modern bullion dealers or arbitragists, which serve to equalise or economise the distribution of the precious metals all over the world. It will be seen at a glance, therefore, that they fulfil, in an automatic and perfectly natural manner, all that was vainly attempted to be accomplished by the repressive savage action of the State, and the interfering unscientific handling of the Mint and coinage rates. It is in this feature that the great distinction between the modern and the seventeenth-century world consists. Such a difference can only be based upon, and have arisen from, a true theory of international trade. But the process of development which alone made it possible--the development of modern banking, the invention of paper currency media, the breaking down of international trade restrictions, all the mechanical and scientific inventions which have resulted in the binding of the world together in one whole as far as commerce is concerned,--all this would comprise in brief the essential features of the complete commercial development of two centuries or more, and how far they are related as cause or effect it would be hard to say. In this secondary period, therefore, the separate history of each individual state gradually loses its distinct or isolated importance, as far as mere Mint edicts are concerned. As a consequence the bimetallic action which we have hitherto sought in the history of each individual currency must now increasingly be sought in the wider field of the world currency, that congeries or completed whole of currency of which each national system now forms only a part, and that not an independent part. France.