The most advantageous employment of any capital to the country to which it belongs is that which maintains there the greatest quantity of productive labour, and increases the most the annual produce of the land and labour of that country. But the quantity of productive labour which any capital employed in the foreign trade of consumption can maintain is exactly in proportion, it has been shown in the second book, to the frequency of its returns. A capital of a thousand pounds, for example, employed in a foreign trade of consumption, of which the returns are made regularly once in the year, can keep in constant employment, in the country to which it belongs, a quantity of productive labour equal to what a thousand pounds can maintain there for a year. If the returns are made twice or thrice in the year, it can keep in constant employment a quantity of