The variations of the different factors may mutually compensate each other, so that notwithstanding their continued instability, the sum of the prices to be realised and the quantity of money in circulation remain constant; consequently, we find, especially if we take long periods into consideration, that the deviations from the average level, of the quantity of money current in any country, are much smaller than we should at first sight expect, apart of course from excessive perturbations periodically arising from industrial and commercial crises, or less frequently, from fluctuations in the value of money.