In ordinary use, and I think it is the most convenient use, wealth comprehends all those things, and those things only, which, directly or indirectly, are made the subjects of purchase and sale, of letting and hiring. For this purpose, they must, in the first place, possess utility, or, in other words, be capable of affording pleasure or preventing pain, since no one would purchase or hire anything absolutely useless. In the second place, they must be limited in supply, since no one would buy anything of which he might acquire as much as he pleased by merely taking possession of it. The water in the open sea is practically unlimited in supply; any one who chooses to go for it, may have as much of it as he pleases. The portion of it which has been brought to London to supply salt water baths is limited, and cannot be obtained, therefore, without payment. In the third place, nothing is wealth that is not capable of appropriation. Fine weather is useful, and is limited in supply, but it is not wealth, since it cannot be appropriated. Some things are capable of appropriation only under peculiar circumstances. In an extensive, thinly inhabited plain, light and air are incapable of appropriation, every inhabitant may enjoy them equally; but in a town, one house intercepts them from another. A town house, surrounded by an open space, has more of them than one in a street. The possessor of such a house, and of the ground which surrounds it, has practically appropriated its peculiar advantages of light and air; they add to its value, and form, therefore, part of his wealth. He even may sell them without parting with his house, by selling the privilege of erecting buildings which will intercept them. Fourthly, as is implied by the definition, nothing can be wealth which is not directly or indirectly transferable. High birth is agreeable and rare, it may add to the happiness of its possessor, but, as it is absolutely incapable of transfer, it is not part of his wealth. Most of our personal qualities are only indirectly transferable; they are transferable, not in themselves, but embodied in the commodities which their possessor can produce, or in the services which he can render. The skill of a painter is transferable in the form of a commodity, his pictures; the skill of a surgeon in that of a service, the dexterity with which he performs an operation. Such qualities perish by the death of the possessor, or may be impaired or destroyed by disease, or rendered valueless by changes in the customs of the country, which put an end to the demand for their products. Even to the same person, and under the same circumstances in all other respects, they may become wealth, or cease to be wealth, merely in consequence of a change in the social position of their possessor. When Miss Linley became Mrs. Sheridan, her powers of action and song ceased to be wealth; they remained the delight of private societies, but were no longer objects of sale.