when their value is considered as remaining the same, the demand will be represented and measured by the sacrifice in money which the demanders are willing and able to make in order to satisfy their wants. In this state of things, the value of commodities in money or their prices are determined by the demand for them, compared with the supply of them. And this law appears to be so general, that probably not a single instance of a change of price can be found, which may not be satisfactorily traced to some previous change in the state of the demand or supply.
In examining the truth of this position, we must constantly bear in mind the terms in which it is expressed; and recollect, that when prices are said to be determined by demand and supply, it is not meant that they are determined either by the demand alone, or by the supply alone, but by their relation to each other. But how is this relation to be determined? It has sometimes been said, that demand is always equal to supply; because no supply of any commodity can take place for which there is not a demand, which will take off all that is offered. In one sense of the terms in which demand and supply have been used, this position may be granted. The actual extent of the demand, compared with the actual extent of the supply are always nearly equal to each other. If the supply be ever so small, the extent of the demand cannot be greater; and if the supply be ever so great, the extent of the demand will in most cases increase in proportion to the fall of price occasioned by the desire to sell, and the consumption will finally equal the production. It cannot, therefore, be in this sense that a change in the proportion of demand to supply takes place; because in this sense demand and supply always bear nearly the same relation to each other. And this uncertainty in the use of these terms, renders it an absolutely necessary preliminary in the present inquiry, clearly to ascertain what is the nature of that change in the relation of demand and supply
