The Wealth of Nations by Part 2 Chapter 2 Page 134

keep the whole quantity of bank money always below what this use occasions a demand for. It is upon this account, they say, that bank money sells for a premium, or bears an agio of four or five per cent above the same nominal sum of the gold and silver currency of the country. This account of the bank of Amsterdam, however, it will appear hereafter, is in a great measure chimerical.

A paper currency which falls below the value of gold and silver coin does not thereby sink the value of those metals, or occasion equal quantities of them to exchange for a smaller quantity of goods of any other kind.

The proportion between the value of gold and silver and that of goods of any other kind depends in all cases not upon the nature or quantity of any particular paper money, which may be current