The reason that the greater part of Europe is more populous now than it was in former times, is that the industry of the inhabitants has made these countries produce a greater quantity of human subsistence. For I conceive that it may be laid down as a position not to be controverted, that, taking a sufficient extent of territory to include within it exportation and importation, and allowing some variation for the prevalence of luxury, or of frugal habits, that population constantly bears a regular proportion to the food that the earth is made to produce. In the controversy concerning the populousness of ancient and modern nations, could it be clearly ascertained that the average produce of the countries in question, taken altogether, is greater now than it was in the times of Julius Caesar, the dispute would be at once determined. When we are assured that China is the most fertile country in the world, that almost all the land is in tillage, and that a great part of it bears two crops every year, and further, that the people live very frugally, we may infer with certainty that the population must be immense, without busying ourselves in inquiries into the manners and habits of the lower classes and the encouragements to early marriages. But these inquiries are of the utmost importance, and a minute history of the customs of the lower Chinese would be of the greatest use in ascertaining in what manner the checks to a further population operate; what are the vices, and what are the distresses that prevent an increase of numbers beyond the ability of the country to support.