The sexual instinct and the love for children are incentives of such universality and power, that an increase of the means of subsistence is uniformly followed by an increase in the numbers of mankind. _Partout, où deux personnes peuvent vivre commodément, il se fait un mariage._ (_Montesquieu._) Thus after a good harvest, the number of marriages and births is wont to considerably increase; and conversely to diminish after bad harvests.[240-1] [240-2] [240-3] In the former case, it is rather hope than actual possession which constitutes the incentive to the founding of new families. Hence the greatest increase is not found in connection with the absolutely lowest price of corn, but with those prices which present the most striking contrast to those of a previous bad year.[240-4] The introduction of the potato has promoted the rapid increase of population in most countries. Thus, the population of Ireland in 1695, was only 1,034,000; in 1654, when the cultivation of the potato became somewhat more common it was 2,372,000; in 1805, 5,395,000; in 1823, 6,801,827; in 1841, 8,175,000. In 1851, after the fearful spread of the potato-rot it fell again to 6,515,000.[240-5] In general, every new or increasing branch of industry, as soon as it yields a real net product is wont to invite an increase of population. Machines, however, have not this effect only when they operate to produce rather a more unequal division of the national income than an absolute increase of that income.[240-6] [Footnote 240-1: That rich food directly increased prolificacy is proved from the fact that, for instance, our domestic animals are much more prolific than wild ones of the same species. Compare _Villermé_, in the Journ. des Economistes VI, 400 ff. The months richest in conceptions fall universally in the spring, and again in the pleasant season immediately following the harvest. On the other hand, during the seasons of fast in the Catholic church the number of cases of conception is below the average. (Jour. des Econ., 1857, 808).] [Footnote 240-2: Thus the annual mean number of marriages amounted to: ============================================= | _Between 1841_ | _In 1847_ | _and 1850._ | _alone._ --------------+----------------+------------- In Saxony, | 15,505 | 14,220 In Holland, | 22,352 | 19,280 In Belgium, | 28,968 | 24,145 In France, | 280,330 | 249,797 =============================================