is true of clay, stone, water, and the commonest kinds of labor. [Sidenote: No scarce goods can be indefinitely increased] It has long been customary for economists to talk of economic goods that could be increased indefinitely (meaning infinitely or, in any event, without any limit ever appreciable to man) without any increase in the cost or scarcity. This class of goods was considered to be very large. There is no such class of economic goods; it is evidently impossible that there should be. If they are already "scarce," increasing demand must make them scarcer. There are, however, some goods that practically can be increased with so little difficulty that their limitation is not of great social importance. Progress, population, prosperity, are not primarily conditioned on their amount; limitation will be felt far earlier elsewhere. They are at one end of the scale; they are the relatively increasable goods. [Sidenote: The products of land are increased at a given time and place at increasing cost] 3. _There is a large class of goods whose increase is seen to be gained with increasing difficulty._ This is seen most clearly in the diminishing returns from land. In the attempt to get some food-products in greater quantity from a given area at a given time, increasing difficulty is met with at once. This attempt continued for a series of years results in historical diminishing returns, as was strikingly illustrated in English experience during the Napoleonic wars, when wheat rose in value because of the greater difficulty of producing the larger supply needed. Some replenishing agents will restore themselves if given time; the forest will grow up if left untouched by man; the field will recover its fertile quality if allowed to lie fallow. But this self-replenishing of agents is a slow process, and time is costly. Man therefore tries in other ways to force more uses out of goods, until checked by the increasing difficulty. The goods subject to "the law of increasing cost," as it was called formerly, were considered to be a peculiar class comprising only a small portion of wealth. But it can now be seen that the law may apply ultimately, though in differing degrees, to every kind of economic goods. Indeed, the principle just discussed is no more than one phase of the law of economic diminishing returns, which has a universal application to the realm of values. [Sidenote: Agents most nearly fixed in amount are somewhat increasable]