According to a recent writer, it is impossible to give any close figures on the number of persons who have lived on this earth. It is generally considered that one person in every thirteen dies each year. At this rate the population would be renewed every thirteen years. Assuming that the population of the world is 1,000,000,000 and that it has been 1,000,000,000 at any time during the last 6,000 years, we find that the population has been renewed about 461 times; that is, that 462,000,000,000 have lived on this earth since its creation. This, of course, is vastly in excess of the real number, for the world, so far as we can tell, is more thickly populated now than ever before. Probably if we were to cut those figures in two we should still be above the actual number, with a total of 231,000,000,000 persons.