The Wealth of Nations by Part 2 Chapter 5 Page 40

surplus must be sent abroad and exchanged for something for which there is a demand at home. Without such exportation a part of the productive labour of the country must cease, and the value of its annual produce diminish. The land and labour of Great Britain produce generally more corn, woollens, and hardware than the demand of the home market requires. The surplus part of them, therefore, must be sent abroad, and exchanged for something for which there is a demand at home. It is only by means of such exportation that this surplus can acquire a value sufficient to compensate the labour and expense of producing it.

The neighbourhood of the sea-coast, and the banks of all navigable rivers, are advantageous situations for industry, only because they facilitate the exportation and exchange of such surplus produce for something else which is more in demand there.