_Varying Demand and Price._--The facts that have just been stated account only in a partial way for the adjustment of market price. One who wishes to trace phenomena to their causes cannot help asking why demand and supply insure the selling of a given amount of goods at one rate rather than at another. If apples are offering at two dollars a barrel, why is it that, in a particular local market, one thousand barrels and no more can, at that rate, be sold? We can readily see that at one dollar a barrel more could be sold than at two, and that at three less would be sold. But why is it that, at two dollars, the definite number of one thousand barrels is the amount that is taken and paid for? Why is the equation of demand and supply established at exactly that price? _Demand and Final Utility._--We come nearer to the cause that acts in adjusting the price of apples when we say that they sell at two dollars a barrel because that sum expresses their "final utility." This means that, if such an auctioning process as we have described were resorted to, the last barrel of apples which would be sold would have to the buyer an amount of utility just equal to that of the final unit of any other article that could have been had for the same money. The auctioning, however, would cause different barrels of apples to sell at different prices, whereas there is something in the working of competition which causes all of them to sell at the same price. It is necessary to see, first, how the price of the "final" one is adjusted and, secondly, how that fixes the price of all the others. _The Law of Diminishing Utility._--We revert here to one of those general laws of economics that we have already stated and see it acting under the conditions of distinctly social life. Goods of a given kind have less and less utility, per unit, the more the user has of them. If you offer him apples in increased quantity, he will value the first part of the supply highly, but will attach less value to the later parts. When the desire for this fruit is fairly well satisfied, he will find other articles of more importance. At the price of two dollars a barrel it is just worth his while to buy a final barrel of them. That quantity, as added to his winter's supply, will give him two dollars' worth of benefit. This means that it will do him as much good as anything else which he can get for the same amount of money.