[Footnote 237d-15: The preparatory steps towards this ideal were taken long ago. Thus, for instance, the personal-property insurance companies have offered premiums for special merit in extinguishing fires (Calenb.-Grubenh., 1814, § 35), saving things from a burning house is looked after by the agents of personal property insurance companies; compensation is almost universally made not only for the damage done by fire, but also that caused while the fire is being extinguished. The excellent fire-extinguishing institutions of England are maintained by the common action of the insurance companies. There have been complaints, however, that they have shown a preference for insured objects. (Mitth., 1874, 113.)] BOOK V. ON POPULATION. CHAPTER I. THEORY OF POPULATION. SECTION CCXXXVIII. INCREASE OF POPULATION IN GENERAL. That amid the thousand dangers which threaten the existence of the individual the species may endure, the Creator has endowed every class of organic beings with such reproductive power, and so much pleasure in propagating their kind, that if the action of these were entirely unrestricted, it would soon fill up the earth.[238-1] In the case of the human race, also, the physiological possibility of propagation has very wide limits.[238-2] It would be nothing extraordinary that a healthy pair, living in wedlock from the 20th to the 42nd year of the woman's life, that is, during the whole time of her full capacity to bear children, should rear six children to the age of puberty. This would, therefore, suffice to treble the population in a single generation; provided that all who had grown up should marry. According to Euler,[238-3] when the births were 5 per cent. and the deaths 2 per cent., the population doubled in not quite 24 years; when the increase was 2½ per annum, in 28 years; when 2, in 35 years, and when 1½ per cent. in 47 years. The United States furnish us with a striking illustration of this doctrine, and on the grandest scale. There the natural increase of the white population, from 1790 to 1840, was 400.4 per cent.; that is in the first decade 33.9 per cent. of the population in 1790; in the second 33.1, in the third 32.1, in the fourth 30.9, in the fifth 29.6 per cent.[238-4] [238-5]