The Wealth of Nations by Part 1 Chapter 11 Page 141

2. Second Period

But how various soever may have been the opinions of the learned concerning the progress of the value of silver during this first period, they are unanimous concerning it during the second.

From about 1570 to about 1640, during a period of about seventy years, the variation in the proportion between the value of silver and that of corn held a quite opposite course. Silver sunk in its real value, or would exchange for a smaller quantity of labour than before; and corn rose in its nominal price, and instead of being commonly sold for about two ounces of silver the quarter, or about ten shillings of our present money, came to be sold for six and eight ounces of silver the quarter, or about thirty and forty shillings of our present money.