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 less facility of purchasing them; and that consequently given portions of them will, in many cases, express most imperfectly the difficulty of obtaining possession of the numerous objects for which they may be exchanged.

If we are told that a certain quantity of cloth in a particular country will exchange for ten ounces of silver, or that the revenue of a particular sovereign, seven or eight hundred years ago, was £400,000 a year, these statements of nominal value do not tell us whether the cloth is obtained with facility or difficulty, or whether the resources of the sovereign are abundant or scanty. Without further information on the subject, we should be quite at a loss to say, whether it would be necessary to sacrifice the worth of ten days labour to obtain the cloth, or a hundred days; whether the king in question might be considered as having a very inadequate revenue; or whether the sum mentioned was so great as to be incredible.*

It is quite obvious that in cases of this kind, and they are of constant recurrence, the values of commodities or incomes estimated in the precious metals, or in other commodities which are subject to considerable variations in the difficulty of obtaining them, may imply an increase or decrease of value merely in name, and would be of little use to us alone.

What we want further to know, is the estimation in which the cloth and money were held in the country, and at the time in question, founded on the desire to possess, and the difficulty of obtaining possession of them. It is truly stated by Mr. Senior, that in comparing two commodities together, the power of one to purchase the other must depend upon two sets of causes, that is, upon the causes which affect the desire to possess, and the difficulty of obtaining possession of one of them, and the causes which affect the