The Wealth of Nations by Part 4 Chapter 7 Page 179

For they did not find it convenient to buy every part of it. Some parts of it imported into England might have interfered with some of the trades which they themselves carried on at home. Those particular parts of it, therefore, they were willing that the colonists should sell where they could- the farther off the better; and upon that account purposed that their market should be confined to the countries south of Cape Finisterre.

A clause in the famous Act of Navigation established this truly shopkeeper proposal into a law.

The maintenance of this monopoly has hitherto been the principal, or more properly perhaps the sole end and purpose of the dominion which Great Britain assumes over her colonies. In the exclusive trade, it is supposed, consists the great advantage of provinces, which