In the case supposed, different portions of the supply of corn have different costs of production. Though the twenty, or fifty, or one hundred and fifty quarters additional have been produced at a cost proportional to 25_s._, the original hundred quarters per annum are still produced at a cost only proportional to 20_s._ This is self-evident, if the original and the additional supply are produced on different qualities of land. It is equally true if they are produced on the same land. Suppose that land of the best quality, which produced one hundred quarters at 20_s._, has been made to produce one hundred and fifty by an expensive process, which it would not answer to undertake without a price of 25_s._ The cost which requires 25_s._ is incurred for the sake of fifty quarters alone: the first hundred might have continued forever to be produced at the original cost, and with the benefit, on that quantity, of the whole rise of price caused by the increased demand: no one, therefore, will incur the additional expense for the sake of the additional fifty, unless they alone will pay for the whole of it. The fifty, therefore, will be produced at their natural price, proportioned to the cost of their production; while the other hundred will now bring in 5_s._ a quarter more than their natural price—than the price corresponding to, and sufficing to remunerate, their lower cost of production. If the production of any, even the smallest, portion of the supply requires as a necessary condition a certain price, that price will be obtained for all the rest. We are not able to buy one loaf cheaper than another because the corn from which it was made, being grown on a richer soil, has cost less to the grower. The value, therefore, of an article (meaning its natural, which is the same with its average value) is determined by the cost of that portion of the supply which is produced and brought to market at the greatest expense. This is the Law of Value of the third of the three classes into which all commodities are divided. § 2. Such commodities, when Produced in circumstances more favorable, yield a Rent equal to the difference of Cost. If the portion of produce raised in the most unfavorable circumstances obtains a value proportioned to its cost of production; all the portions raised in more favorable circumstances, selling as they must do at the same value, obtain a value more than proportioned to their cost of production.