General, or at least universal, changes of Prices in rise or fall in any given country are due to general and great changes in the Money current there. Subordinate changes in other valuables, money being supposed to remain uniform, will of course vary their Prices; but it is impossible that such changes should affect equally or even generally all the various and numberless valuables of a whole country; while some are coming easier, others are coming harder, while some are more desired than formerly others are less desired, and this will bring in of course altered prices, some higher and some lower; but a general rise of all prices, or a general fall in the same, can only come about by great changes of some kind in the circulating medium, that is, the money, of the country. For example, in the United States, between 1862 and 1878 inclusive, a government paper promise, called _greenbacks_, was the current money of the country; owing to its excessive issue, and to some doubt in the minds of the people whether the paper would ever be redeemed in gold, it soon became depreciated as compared with gold, the premium on which over the paper money varied at different times from 1 to 185 _per centum_; as all other valuables were then sold against greenback money, which had declined, their prices naturally rose in some sort of proportion as the medium fell; general _values_ remained much as before, but general _prices_ were much enhanced; and when, after the resumption of specie payments in January, 1879, gold became again the standard medium, general prices declined in full accordance with the same universal principle reversed. (b) Prices, as we have now seen, are only a subordinate form of Values: the universal law that regulates all the variations of them both, within certain fixed limits to be examined shortly, is called the LAW OF SUPPLY AND DEMAND. This is perhaps the most comprehensive and beautiful law in Political Economy. We shall look at it now only in outline: the filling in will be the pastime and profit of all that is to come.