It is possible, therefore, that the total utility of anything, like a paper of tacks, for instance, may be greatly increased, since it has indefinitely more uses than when tacks were first made. Yet the supply of tacks is so enormous that to consume them we must use them for trifling purposes; and therefore their value is a trifle. When we have water to throw away, its value is nothing. When water is limited to culinary uses, its value is considerable. When water is sufficient only to slake extreme thirst, its value is beyond price. Even the prospect of a future supply diminishes the utility of any commodity, since time is an important element in satisfaction. Thus a store of potatoes in early spring, however well preserved, has its final utility lowered, and therefore its value lessened, by the prospect of new potatoes. On the other hand, the present value of a field of grain or the young orchard is dependent upon its utility in meeting a future want. Everything which enhances prospective utility of any article enhances its value; and everything which diminishes the chance of such utility, like bad weather, insects or plant diseases, diminishes the present value. In this way risk diminishes the value of wealth subject to it and increases the value of wealth which has passed by it. In general, the usefulness of anything is no criterion for measuring value, because other elements of value are more important. Henry C. Carey says, “Utility is the measure of man’s power over nature; value is the measure of nature’s power over man.” This may be a striking way of saying that great utility implies a discovery of uses, while great value often indicates only difficulty in securing what has great usefulness. _Exertion as related to value._—Since utility, however essential to value, is not its measure, we are led to consider whether the exertion required to obtain any article desired may not measure its worth. This is certainly a matter of prime consideration, and many have been led to suppose the cost of production, by which is meant all the exertion necessary to bring any commodity to its final consumer, to be the sole and absolute measure of value.