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 tion, I have thought that the subject would be best illustrated by referring first to those periods in which the value of money is practically considered as constant; and it is allowed that during such periods, it is the uniform practice of society to represent demand by money. But it is evident that we cannot extend these periods to any considerable length. We well know, that although the precious metals, from their durability, and the consequent steadiness of their supply, are subject to slow changes of value; yet that at distant periods, and in different countries, their value has been, and is, essentially different.

It is absolutely necessary, therefore, to consider how a demand may be represented and measured under any changes which may take place in the value of money.

An effectual demand for a commodity, is such a demand as will fulfill the natural and necessary conditions of the supply; or, as it has been defined, it is the sacrifice which the demanders must make in order to effectuate the continued supply of the commodity in the quantity required under the actual circumstances.

Now it is obvious, that if money varies essentially, as compared with the natural and necessary conditions of the supply of commodities, a given amount of money cannot possibly represent a given demand, or a given sacrifice.

In every country there are a few commodities obtained by labour alone; and, if the advance of a certain quantity of labour be the necessary condition of the supply of a particular commodity, then the money which will command such labour will represent the effectual demand for the commodity; that is, a demander able and willing to make such a sacrifice as will effectuate the supply. But if, subsequently, money falls in value in relation to the required labour, the same quantity of money obviously ceases to represent the same demand. No one, I apprehend, would venture to affirm that an ounce of pure silver, applied