Commerce is necessary, however, not only to exchange local products, but local skill. Labour requiring the agency of fire can only be given abundantly in cold countries; labour requiring suppleness of body and sensitiveness of touch only in warm ones; labour involving accurate vivacity of thought only in temperate ones; while peculiar imaginative actions are produced by extremes of heat and cold, and of light and darkness. The production of great art is limited to climates warm enough to admit of repose in the open air, and cool enough to render such repose delightful. Minor variations in modes of skill distinguish every locality. The labour which at any place is easiest, is in that place cheapest; and it becomes often desirable that products raised in one country should be wrought in another. Hence have arisen discussions on "International values," which will be one day remembered as highly curious exercises of the human mind. For it will be discovered, in due course of tide and time, that international value is regulated just as inter-provincial or inter-parishional value is. Coals and hops are exchanged between Northumberland and Kent on absolutely the same principles as iron and wine between Lancashire and Spain. The greater breadth of an arm of the sea increases the cost, but does not modify the principle of exchange; and a bargain written in two languages will have no other economical results than a bargain written in one. The distances of nations are measured not by seas, but by ignorances; and their divisions determined, not by dialects, but by enmities. Of course, a system of international values may always be constructed if we assume a relation of moral law to physical geography; as, for instance, that it is right to cheat across a river, though not across a road; or across a lake, though not across a river; or over a mountain, though not across a lake, etc.:--again, a system of such values may be constructed by assuming similar relations of taxation to physical geography; as, for instance, that an article should be taxed in crossing a river, but not in crossing a road; or in being carried over a mountain, but not over a ferry, etc.: such positions are indeed not easily maintained when once put in logical form; but one law of international value is maintainable in any form; namely, that the farther your neighbour lives from you, and the less he understands you, the more you are bound to be true in your dealings with him; because your power over him is greater in proportion to his ignorance, and his remedy more difficult in proportion to his distance.