We are now in a position to enumerate the causes which actually lead to an increase in the population of a country.  The first is an increase in the amount of food produced in the country itself.  If the parks and gardens of the gentry were ploughed up or turned into allotments, a few hundred thousands would be added to the population of the United Kingdom, at the cost of one of the few remaining beauties which make our country attractive to the eye.  The introduction of the potato into Ireland added several millions of squalid inhabitants to that ill-conditioned island, and when the crop failed, large numbers of them inflicted themselves on the United States, to the detriment of that country.  The richest countries to-day are those which produce more food than they require, such as the United States, Canada, Australia, Roumania, and the Argentine. (We need hardly say that throughout this survey we are using the statistics of the years immediately before the war.) But this state of things cannot last long, for the net increase in such countries is invariably high, either by reason of a very high birth-rate, as in Roumania, or because newcomers flock in to enjoy a land of plenty.  Another condition which leads to abnormally rapid increase is found when a civilised nation conquers and administers a backward country, introducing better methods of agriculture, and especially irrigation and the reclamation of waste lands.  The alien Government also gives greater security, without raising the standard of living among the natives, since the dominant race usually monopolises the lucrative careers.  In this way we are directly responsible for increasing the population of Egypt from seven millions in 1883 to nine and three-quarter millions in 1899, an augmentation which, in the absence of immigration, illustrates the great natural fertility of the human race in the rare circumstances when unchecked increase is possible.  Still more remarkable is the rise in the population of Java from five millions in 1825 to twenty-eight and a half millions in the first decade of this century.  The cause of this increase is the augmented supply of food combined with a very low standard of living, a combination which is specially characteristic of Asia, where extreme supersaturation exists in India and China.  A third cause is production of goods which can be exchanged for food grown abroad.  This exchange, as we have seen, is stimulated by the presence of capital seeking employment.  Our large towns are the creation of the capitalist, much more than if he had populated their depressing streets with his own children.  Fourthly, a reduction in the standard of living of course makes a larger population possible.  The misery of the working class in the generation after the Napoleonic Wars was a condition of the prosperity of our export trade at this period; and conversely, the prosperity of our export trade was necessary to the existence of the new inhabitants.  Capitalism is the cause of our dense population; and the proletariat would infallibly cut their own throats by destroying it.