On the other hand, substances may be very valuable which have cost little or no labour. When a shepherd in Australia happens to pick up a nugget of gold on the mountain side, it takes no labour worth mentioning to pick it up, yet the gold is just as valuable in proportion to its weight as any other gold. Some gold mines produce a great quantity of gold: others which have cost quite as much to sink, produce little; nevertheless the gold out of the one mine is sold at the same price in proportion to its weight and fineness as that out of the other mine. #Thus it is quite certain that labour is not the cause of value.# Gold is valuable because a great many people want more gold than they have already got, and whenever a thing is valuable it is because somebody wants it. But we may look at this matter in another way. If it were possible to get a valuable thing like gold with little labour, many people would become gold miners. Much gold would then be produced; if this were wanted as much as what was already in use, it would be as valuable. But no one wants an unlimited quantity of any substance. Wealth, as we saw, must be limited in supply; if gold became as plentiful as lead or iron, it could not possibly remain as valuable as it is now. People would have far more than they could employ for ornaments, watches, gilding and so forth; there would be a large surplus to be used in making pots and pans, for which it is less needed. Now we can see through the whole subject of value. When much of a substance can usually be produced with little labour, the substance becomes so plentiful that people are satisfied with the supplies of it which they have; they do not want more, or at least do not want it so urgently. It follows that they are unwilling to give much wealth for it. Thus the labour spent upon producing a commodity does not affect the value of that commodity, unless it alters the quantity of it which people can get, and thus makes a further supply of the commodity more or less useful than before.