The Wealth of Nations by Part 1 Chapter 11 Page 195

mines, therefore, varies, perhaps, still more from year to year than that of the greater part of corn fields, those variations have not the same effect upon the price of the one species of commodities as upon that of the other.

VARIATIONS IN THE PROPORTION BETWEEN THE RESPECTIVE VALUES OF GOLD AND SILVER

Before the discovery of the mines of America, the value of fine gold to fine silver was regulated in the different mints of Europe between the proportions of one to ten and one to twelve; that is, an ounce of fine gold was supposed to be worth from ten to twelve ounces of fine silver. About the middle of the last century it came to be regulated, between the proportions of one to fourteen and one to fifteen; that is, an ounce of fine gold came to be supposed to be worth between fourteen and fifteen ounces of fine silver.