years ago, though so thinly peopled in comparison to the present population, it is probable that the worst land under the plow was, from the rude state of agriculture, quite as unproductive as the worst land now cultivated, and that cultivation had approached as near to the ultimate limit of profitable tillage in those times as in the [pg 494] present. What the agricultural improvements since made have really done is, by increasing the capacity of production of land in general, to enable tillage to extend downward to a much worse natural quality of land than the worst which at that time would have admitted of cultivation by a capitalist for profit; thus rendering a much greater increase of capital and population possible, and removing always a little and a little further off the barrier which restrains them; population meanwhile always pressing so hard against the barrier that there is never any visible margin left for it to seize, every inch of ground made vacant for it by improvement being at once filled up by its advancing columns. Agricultural improvement may thus be considered to be not so much a counter-force conflicting with increase of population as a partial relaxation of the bonds which confine that increase.
If a great agricultural improvement were suddenly introduced, it might throw back rent for a considerable space, leaving it to regain its lost ground by the progress of population and capital, and afterward to go on further. But taking place, as such improvement always does, very gradually, it causes no retrograde movement of either rent or cultivation; it merely enables the one to go on rising, and the other extending, long after they must otherwise have stopped.
Inasmuch as, in point of fact, B never gets the start of A, but follows along with A, the general result will be that