The other factor, which is really promoting the gradual disappearance of the Anglo-Saxons from the United States, is of a very different character.  The descendants of the old immigrants are on the whole the aristocracy of the country.  Now it is a law which hardly admits of exceptions, that aristocracies do not maintain their numbers.  The ruling race rules itself out; nothing fails like success.  Gibbon has called attention to the extreme respect paid to long descent in the Roman Empire, and to the strange fact that, in the fourth century, no ingenuity of pedigree makers could deny that all the great families of the Republic were extinct, so that the second-rate plebeian family of the Anicii, whose name did appear in the Fasti, enjoyed a prestige far greater than that of the Howards and Stanleys in this country.  Our own peerage consists chiefly of parvenus.  Only six of our noble families, it is said, can trace their descent in the male line without a break to the fifteenth century.  The peerage of Sweden tells the same tale.  According to Gallon, the custom or law of primogeniture, combined with the habit of marrying heiresses who, as the last representatives of dwindling families, tend to be barren, is mainly responsible for this.  Additional causes may be the greater danger which the officer-class incurs in war, and, in former times, the executioner’s axe.  In our own day the reluctance of rich and self-indulgent women to bear children is undoubtedly a factor in the infertility of the leisured class.

This brings us naturally to the second part of our discussion—­the consideration of the causes which lead to the increase or decrease of population.  It is the most important part of our inquiry; for it is usually assumed that the British Isles will continue to send out colonists in large numbers, as it did in the last century, and the hopes of the imperialist that a large part of the world will speak English for all time depend on the untested assurance that the swarming-time of our race is not yet over.  Our starting-point must be that the pressure of population upon the means of subsistence is a constant fact in the human race, as in every other species of animals and plants.  There is no species in which the numbers are not kept down, far below the natural capacity for increase, by the limitation of available food.  It may not always be easy to trace the connection between the appearance of new lives and the passing away of old, nor to say whether it is the birth-rate which determines the death-rate, or the death-rate the birth-rate.  But it is well known that, wherever statistics are kept, the numbers of births and of deaths rise and fall in nearly parallel lines, so that the net rate of increase hardly alters at all, unless some change, which can easily be traced, occurs in the habits of the people or in the amount of the food supply.  In civilised countries the greater care taken of human life, and its consequent prolongation,