Assuming prices of production to remain unchanged, the additional investments of capital in the better soils, that is, in all soils from B upward may be made with unaltered, increasing, or decreasing productivity. For soil A this would only be possible under the conditions assumed by us, if productivity remains the same — whereby the land continues to yield no rent — and also if productivity increases; a portion of the capital invested in A would then yield rent, while the remainder would not. But it would be impossible if productivity on A were to decrease, for then the price of production would not remain unchanged, but would rise. Yet in all these cases, i.e., whether the surplus-product yielded by the additional investments is proportional to the latter or is greater or smaller than this proportion — whether, therefore, the rate of surplus-profit on the capital remains constant, rises or falls, when this capital increases, the surplus-product and the corresponding surplus-profit per acre increases, and hence also the potential rent in grain and money. The growth in the mere quantity of surplus-profit or rent, calculated per acre, that is, an increasing quantity calculated on the basis of some constant unit — in the present case on a definite quantity of land such as an acre or a hectare — expresses itself as an increasing ratio. Hence the magnitude of the rent, calculated per acre, increases under such circumstances simply in consequence of the increase in the capital invested in the land. This takes place, to be sure, assuming the prices of production remain the same, and, on the other hand, regardless of whether the productivity of the additional capital remains unaltered, or whether it decreases or increases. The latter circumstances modify the range in which the magnitude of rent per acre increases but not the existence of this increase itself. This is a phenomenon peculiar to differential rent II, and distinguishing it from differential rent I. If the additional investments of capital were made successively in space, side by side in new additional soil of corresponding quality, rather than successively in time in the same soil, the quantity of the rental would have increased, and, as previously shown, so would the average rent from the total cultivated area, but not the magnitude of the rent per acre. Given the same result so far as quantity and value of total production and surplus-product are concerned, the concentration of capital upon a smaller area of land increases the amount of rent per acre, whereas under the same conditions, its dispersion over a larger area, all other conditions being equal, does not produce this effect. But the more the capitalist mode of production develops, the more does the concentration of capital upon the same area of land develop, and, therefore, the more does the rent, calculated per acre, increase. Consequently, given two countries in which the prices of production are identical, the differences in soil type are identical, and the same amount of capital is invested — but in the one country more in the form of successive outlays upon a limited area of land, whereas in the other more in the form of co-ordinated outlays upon a larger area — then the rent per acre, and thereby the price of land, would be higher in the first country and lower in the second, although the total rent would be the same for both countries. The difference in magnitude of rent could thus not be explained here to be a result of a difference in the natural fertility of the various soils, nor a result of a difference in the quantity of employed labour, but solely a result of different ways in which the capital is invested.