The Wealth of Nations by Part 4 Chapter 1 Page 19

industry can either purchase or produce naturally regulates itself in every country according to the effectual demand, or according to the demand of those who are willing to pay the whole rent, labour, and profits which must be paid in order to prepare and bring it to market.

But no commodities regulate themselves more easily or more exactly according to this effectual demand than gold and silver; because, on account of the small bulk and great value of those metals, no commodities can be more easily transported from one place to another, from the places where they are cheap to those where they are dear, from the places where they exceed to those where they fall short of this effectual demand. If there were in England, for example, an effectual demand for an additional quantity of gold, a packet-boat could bring from