Germany the utmost might be an increase every twenty-five years equal to the present produce. But the continuance of this would mean that in the next two hundred years every farm should produce eight times what it does now, or, in five hundred years, twenty times as much; and even this is incredible, though it would be only an arithmetical progression. No doubt almost all parts of the earth are now more thinly peopled than their capacities might allow; but the difficulty is to use the capacities. That this view of Malthus need not imply any ignorance or any disregard of the resources of high farming may be judged from the fact that our highest agricultural authority, who recognizes the power of English farming to provide on emergency even for our entire annual wants, admits at the same time that, “where full employment and the means of subsistence are abundant, population increases in geometrical progression, and therefore in a far more rapid proportion than the increased productiveness of the soil, which after a certain point is stationary.”[135] “It follows necessarily” (sums up Malthus) “that the average rate of the actual increase of population over the greatest part of the globe, obeying the same law as the increase of food, must be totally of a different character from the rate at which it would increase if unchecked.” On no single farm could the produce be so increased as to keep pace with the geometrical increase of population; and what is true of a single farm is true in this case of the whole earth. Machinery and invention can do less in agriculture than in manufacture, and they can never do so much as to make preventive checks unnecessary.[136]