It is, in fact, by means of this same steadiness of value in the precious metals, which they derive from their great durability, and the consequent uniformity of their supply in the market, that they are enabled to perform their most important functions. Hops, or corn, as before stated, will measure the relative values of commodities at the same time and place; but let the author or reader attempt to estimate the profits of a capitalist in hops or corn, by the excess of the value of his advances above the value of his returns so estimated, and he will soon be bewildered. If a very plentiful year of corn were to succeed to a comparatively scarce one, the farmer, estimating both his outgoings and incomings in the corn of each year, might appear to gain above fifty per cent., while, in reality, he might have lost, and might not be able, without trenching on his capital, to employ as many men on his farm as the year before. On the other hand, if a comparatively scarce year were to succeed to a plentiful one, his profits, estimated in corn, might appear to be less than nothing, and yet he might have been an unusual gainer, in reference to his general power of purchasing labour and other commodities, except corn. If the hop-planter were to estimate his advances and returns in hops, it is obvious that the results would be of the same kind, but aggravated in degree. It must be allowed, then, that the commercial world have acted most wisely in selecting, for their practical measure of value, a commodity which is not only peculiarly convenient in its form, but is, in general, subject only to slow changes of value; and possesses, therefore, that steadiness in its power of purchasing labour and commodities, without which, all confidence in carrying on mercantile enterprises, of any duration, would be at an end. But though the precious metals are a very useful and excellent measure of value for those periods, within which almost all mercantile transactions are begun and completed; yet, as Adam Smith very justly observes, they are not so for very long periods; not because there is no function for them to perform, but because, in the course of four hundred years, they are found to lose that uniformity of value, which, in general, they retain so well during four years.