The Wealth of Nations by Part 4 Chapter 1 Page 65

Its two great engines for enriching the country, therefore, were restraints upon importation, and encouragements to exportation.

The restraints upon importation were of two kinds.

First, restraints upon the importation of such foreign goods for home consumption as could be produced at home, from whatever country they were imported.

Secondly, restraints upon the importation of goods of almost all kinds from those particular countries with which the balance of trade was supposed to be disadvantageous.

Those different restraints consisted sometimes in high duties, and sometimes in absolute prohibitions.

Exportation was encouraged sometimes by drawbacks, sometimes by bounties, sometimes by