of flour used by the man. In the manner in which it is conceived and measured this gain has a kinship to genuine rent. This surplus is an effect on a man himself. It is not anything outward or tangible. It exists only in the man's sensations, and is as far as possible from being a concrete income in material form traceable to some particular agent. It can be measured and described in ways that are quite akin to the manner in which the product of land is measured and described. Each consists of the sum of a series of surpluses or differential amounts, and each, moreover, represents a gain which is not offset by any corresponding subjective cost. The rent of land must be paid by an _entrepreneur_ and is a cost in the same sense in which wages and interest are so; but the owner of the land did not create it by personal effort or sacrifice. Analogies between the product of land, or rent, and the special gains of consumers from the more important parts of their consumption do exist, but they are overbalanced by essential differences; and it is better to use the term _rent_ only in describing the specific contribution to the material product of industry which a concrete and material agent makes. CHAPTER XI LAND AND ARTIFICIAL INSTRUMENTS One may hire many things besides land and pay what is commonly called rent for them. No one would think of calling by any other term the amount paid for the use of a building, a room in a building, or the furniture in the room. All these things yield rent to their owners; and if the intuitions which govern the common use of terms are to be trusted, the income derived from such things and that derived from land have some essential qualities in common. Every such income is paid for the use of some concrete instrument, and is measured, not by a percentage on the value of the instrument, but by a lump sum--a certain number of dollars per month or per year.