value of the wheat declined, it is not meant that the wheat became less useful; value, in political economy, is not determined by usefulness, although if a thing were utterly useless it would have no value whatever; the value of a thing is what you can get in exchange for it; everything therefore that has value must not only be useful in itself, but there must also be some degree of difficulty in obtaining it. The greater this difficulty is, the higher is the value of the commodity. Thus, the difficulty of getting a sea-water bath in your house when you are staying at the sea-side is very small; it consists only of carrying the water a short distance from the sea. The value of the water would therefore be very small. But if you want a sea-water bath in Central Africa, the difficulty in obtaining it would be very great, and the value of the water proportionately increased. The usefulness of the bath in the two places may be imagined to be exactly the same; the difference in value is caused by difference in the difficulty of obtaining it. The value of the wheat therefore gradually
