the force which urges cultivation in this downward course, is the increase of people; while the counter-force which checks the descent, is the improvement of agricultural science and practice, enabling the same soil to yield to the same labour more ample returns. The costliness of the most costly part of the produce of cultivation, is an exact expression of the state, at any given moment, of the race which population and agricultural skill are always running against each other.
§ 2.It is well said by Dr. Chalmers, that many of the most important lessons in political economy are to be learnt at the extreme margin of cultivation, the last point which the culture of the soil has reached in its contest with the spontaneous agencies of nature. The degree of productiveness of this extreme margin, is an index to the existing state of the distribution of the produce among the three classes, of labourers, capitalists, and landlords.
When the demand of an increasing population for more food cannot be satisfied without extending cultivation to less fertile land, or incurring additional outlay, with a less proportional return, on land already in cultivation, it is a necessary condition of this increase of agricultural produce, that the value and price of that produce must first rise. But as soon as the price has risen sufficiently to give to the additional outlay of capital the ordinary profit, the rise will not go on still further for the purpose of enabling the new land, or the new expenditure on old land, to yield rent as well as profit. The land or capital last put in requisition, and occupying what Dr. Chalmers calls the margin of cultivation, will yield, and continue to yield, no rent. But if this yields no rent, the rent afforded by all other land or agricultural capital will be exactly so much as it produces more than this. The price of food will always on the average be such, that the worst laud, and the least productive instalment of the capital employed on the better lauds, shall just replace the
