Gold and silver are no doubt subject to fluctuations, from the discovery of new and more abundant mines; but such discoveries are rare, and their effects, though powerful, are limited to periods of comparatively short duration. They are subject also to fluctuation, from improvements in the skill and machinery with which the mines may be worked; as in consequence of such improvements, a greater quantity may be obtained with the same labour. They are further subject to fluctuation from the decreasing produce of the mines, after they have yielded a supply to the world, for a succession of ages. But from which of these sources of fluctuation is corn exempted? Does not that also vary, on one hand, from improvements in agriculture, from improved machinery and implements used in husbandry, as well as from the discovery of new tracts of fertile land, which in other countries may be taken into cultivation, and which will affect the value of corn in every market where importation is free? Is it not on the other hand subject to be enhanced in value from prohibitions of importation, from increasing population and wealth, and the greater difficulty of obtaining the increased supplies, on account of the additional quantity of labour which the cultivation of inferior lands requires? Is not the value of labour equally variable; being not only affected, as all other things are, by the proportion between the supply and demand, which uniformly varies with every change in the condition of the community, but also by the varying price of food and other necessaries, on which the wages of labour are expended? In the same country double the quantity of labour may be required to produce a given quantity of food and necessaries at one time, that may be necessary at another, and a distant time; yet the labourer's reward may possibly be very little diminished. If the labourer's wages at the former period, were a certain quantity of food and necessaries, he probably could not have subsisted if that quantity had been reduced. Food and necessaries in this case will have risen 100 per cent. if estimated by the _quantity_ of labour necessary to their production, while they will scarcely have increased in value, if measured by the quantity of labour for which they will _exchange_. The same remark may be made respecting two or more countries. In America and Poland, a year's labour will produce much more corn than in England. Now, supposing all other necessaries to be equally cheap in those three countries, would it not be a great mistake to conclude, that the quantity of corn awarded to the labourer, would in each country be in proportion to the facility of production?