The Wealth of Nations by Part 4 Chapter 3 Page 70

In the trade between the southern coast of England and the northern and north-western coasts of France, the returns might be expected, in the same manner as in the inland trade, four, five, or six times in the year. The capital, therefore, employed in this trade could in each of the two countries keep in motion four, five, or six times the quantity of industry, and afford employment and subsistence to four, five, or six times the number of people, which an equal capital could do in the greater part of the other branches of foreign trade. Between the parts of France and Great Britain most remote from one another, the returns might be expected, at least, once in the year, and even this trade would so far be at least equally advantageous as the greater part of the other branches of our foreign European trade.