which they can purchase or command, rises in times of poverty and distress, and sinks in times of opulence and prosperity, which are always times of great abundance; for they could not otherwise be times of opulence and prosperity Corn is a necessary, silver is only a superfluity. Whatever, therefore, may have been the increase in the quantity of the precious metals, which, during the period between the middle of the fourteenth and that of the sixteenth century, arose from the increase of wealth and improvement, it could have no tendency to diminish their value, either in Great Britain, or in any other part of Europe. If those who have collected the prices of things in ancient times, therefore, had, during this period, no reason to infer the diminution of the value of silver from any observations which they had made upon the prices either of corn, or of other commodities, they had still less reason to infer it from any supposed increase of wealth and improvement. _Second Period._--But how various soever may have been the opinions of the learned concerning the progress of the value of silver during the 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. The discovery of the abundant mines of America seems to have been the sole cause of this diminution in the value of silver, in proportion to that of corn. It is accounted for, accordingly, in the same manner by every body; and there never has been any dispute, either about the fact, or about the cause of it. The greater part of Europe was, during this period, advancing in industry and improvement, and the demand for silver must consequently have been increasing; but the increase of the supply had, it seems, so far exceeded that of the demand, that the value of that metal sunk considerably. The discovery of the mines of America, it is to be observed, does not seem to have had any very sensible effect upon the prices of things in England, till after 1570; even though the mines of Potosi had been discovered more than twenty years before.