It has been the opinion, however, of the greater part of those who have written upon the prices of commodities in ancient times, that from the Conquest, perhaps from the invasion of Julius Cæsar, till the discovery of the mines of America, the value of silver was continually diminishing. This opinion they seem to have been led into, partly by the observations which they had occasion to make upon the prices both of corn and of some other parts of the rude produce of land; and partly by the popular notion, that as the quantity of silver naturally increases in every country with the increase of wealth, so its value diminishes as its quantity increases.
In their observations upon the prices of corn, three different circumstances seem frequently to have misled them.
First, In ancient times almost all rents were paid in kind; in a certain quantity of corn, cattle, poultry, etc. It sometimes happened, however, that the landlord would stipulate, that he should be at liberty to demand of the tenant, either the annual payment in kind, or a certain sum of money instead of it. The price at which the payment in kind was in this manner exchanged for a certain sum of money is in Scotland called the conversion price. As the option is always in the landlord to take either the substance or the price, it is necessary for the safety of the tenant, that the conversion price should rather be below than above the average market price. In many places, accordingly, it is not much above one-half of this price. Through the greater part of Scotland this custom still continues with regard to poultry, and in some places with regard to cattle. It might probably have continued to take place, too, with regard to corn, had not the institution of the public fiars put an end to it. These are annual valuations, according to the judg-
