has been found to double itself in fifteen years. Even this extraordinary rate of increase is probably short of the utmost power of population."
The "power of increase" of the human species, according to John Stuart Mill, "is indefinite, and the actual multiplication would be extraordinarily rapid, if the power were exercised to the utmost. It never is exercised to the utmost, and yet, in the most favourable circumstances known to exist, which are those of a fertile region colonized from an industrious and civilized community, population has continued for several generations, independently of fresh immigration, to double itself in not much more than twenty years. . . . It is a very low estimate of the capacity of increase, if we only assume that in a good sanitary condition of the people, each generation may be double the number of the generation which preceded it." James Mill wrote: "That population therefore has such a tendency to increase as would enable it to double itself in a small number of years, is a proposition resting on the strongest evidence, which nothing that deserves the name of evidence has been brought on the other side to oppose."
Mr. McCulloch tells us that "it has been established beyond all question that the population of some of the states of North America, after making due allowance for immigration, has continued to double for a century past in so short a period as twenty, or at most five-and-twenty years." M. Moreau de Jonnès gives us the following table of the time in which the population of each of the under-mentioned countries would double itself:—
| Turkey | would take | … | … | 555 | years |
| Switzerland | would take„ | … | … | 227 | years„ |
| France | would take„ | … | … | 138 | years„ |
| Spain | would take„ | … | … | 106 | years„ |
| Holland | would take„ | … | … | 100 | years„ |
| Germany | would take„ | … | … | 76 | years„ |
| Russia | would take„ | … | … | 43 | years„ |
| England | would take„ | … | … | 43 | years„ |
| United States | would take„ | … | … | 25 | years„ |
| (Without reckoning immigrants.) | |||||
We shall take but a narrow view of the law of population if we confine ourselves exclusively to human beings. Man is but the highest in the animal kingdom, not a creature apart from it, and the law of population runs through the
