knowledge, would form a part of the science of political economy. It will be necessary, therefore, to place some limit upon our investigations; and the necessary limitation is provided by assuming that the facts which are acquired from other sciences are known, or at any rate are supposed to be true. Thus political economy assumes all that we can tell at the present time with regard to the fertility of the soil. It is not the business of political economy to decide whether chemistry can suggest any particular manure which will greatly increase the productiveness of the land; but if the land, by any such cause, is rendered more fertile, then political economy would trace the consequences of this increased fertility upon the production, the distribution, and the exchange of wealth. Again, it would be foreign to the subject of political economy to prove, by a physiological argument, the causes upon which the inferior strength of the French and Russian labourers depends; but political economy, assuming that this inferiority exists, without explaining its cause, or suggesting a remedy for its removal, traces its consequences upon the production, the distribution, and the exchange of wealth.
Returning now to the immediate subject of this chapter; we have to consider the productiveness of the land, labour, and capital, not as they depend on physical causes, but as they are determine by production on a large and small scale, by division of labour, by the accumulation of capital in joint-stock companies, and by various other such circumstances which we shall proceed to notice.
The productiveness of land.The productiveness of land does not depend entirely upon its fertility; for the quantity of labour and capital which may be required to make the produce raised from the land available for consumption forms a very important element in estimating its productiveness. The rich alluvial plains of the Mississippi are almost unsurpassed in fertility; but a considerable portion of the wheat which is grown there is consumed in Europe; and the cost of carrying this wheat to the European markets is virtually so much deducted from the productiveness of the soil upon which the wheat was grown. When the valley of the Mississippi possesses population