Now, in a state of society in which the existing power of labor served to satisfy all material desires, and there was no possibility of new desires being called forth by the opportunity of gratifying them, the effect of labor-saving improvements would be simply to reduce the amount of labor expended. But such a state of society, if it can anywhere be found, which I do not believe, exists only where the human most nearly approaches the animal. In the state of society called civilized, and which in this inquiry we are concerned with, the very reverse is the case. Demand is not a fixed quantity, that increases only as population increases. In each individual it rises with _his_ power of getting the things demanded. Man is not an ox, who, when he has eaten his fill, lies down to chew the cud; he is the daughter of the horse leech, who constantly asks for more. “When I get some money,” said Erasmus, “I will buy me some Greek books and afterward some clothes.” The amount of wealth produced is nowhere commensurate with the desire for wealth, and desire mounts with every additional opportunity for gratification. This being the case, the effect of labor-saving improvements will be to increase the production of wealth. Now, for the production of wealth, two things are required—labor and land. Therefore, the effect of labor-saving improvements will be to extend the demand for land, and wherever the limit of the quality of land in use is reached, to bring into cultivation lands of less natural productiveness, or to extend cultivation on the same lands to a point of lower natural productiveness. And thus, while the primary effect of labor-saving improvements is to increase the power of labor, the secondary effect is to extend cultivation, and, where this lowers the margin of cultivation, to increase rent. Thus, where land is entirely appropriated, as in England, or where it is either appropriated or is capable of appropriation as rapidly as it is needed for use, as in the United States, the ultimate effect of labor-saving machinery or improvements is to increase rent without increasing wages or interest. It is important that this be fully understood, for it shows that effects attributed by current theories to increase of population are really due to the progress of invention, and explains the otherwise perplexing fact that labor-saving machinery everywhere fails to benefit laborers. Yet, to grasp fully this truth, it is necessary to keep in mind what I have already more than once adverted to—the interchangeability of wealth. I refer to this again, only because it is so persistently forgotten or ignored by writers who speak of agricultural production as though it were to be distinguished from production in general, and of food or subsistence as though it were not included in the term wealth.