As for the time in which the people double, it is yet more hard to be found.  For we have good experience (in the said page 94 of the aforementioned observations) that in the country but 1 of 50 die per annum; and by other late accounts, that there have been sometimes but 24 births for 23 burials.  The which two points, if they were universally and constantly true, there would be colour enough to say that the people doubled but in about 1,200 years.  As, for example, suppose there be 600 people, of which let a fiftieth part die per annum, then there shall die 12 per annum; and if the births be as 24 to 23, then the increase of the people shall be somewhat above half a man per annum, and consequently the supposed number of 600 cannot be doubled but in 1,126 years, which, to reckon in round numbers, and for that the aforementioned fractions were not exact, we had rather call 1,200.

There are also other good observations, that even in the country one in about 30 or 32 per annum hath died, and that there have been five births for four burials.  Now, according to this doctrine, 20 will die per annum out of the above 600, and 25 will be born, so as the increase will be five, which is a hundred and twentieth part of the said 600.  So as we have two fair computations, differing from each other as one to ten; and there are also several other good observations for other measures.

I might here insert, that although the births in this last computation be 25 of 600, or a twenty-fourth part of the people, yet that in natural possibility they may be near thrice as many, and near 75.  For that by some late observations, the teeming females between 15 and 44 are about 180 of the said 600, and the males of between 18 and 59 are about 180 also, and that every teeming woman can bear a child once in two years; from all which it is plain that the births may be 90 (and abating 15 for sickness, young abortions, and natural barrenness), there may remain 75 births, which is an eighth of the people, which by some observations we have found to be but a two-and-thirtieth part, or but a quarter of what is thus shown to be naturally possible.  Now, according to this reckoning, if the births may be 75 of 600, and the burials but 15, then the annual increase of the people will be 60; and so the said 600 people may double in ten years, which differs yet more from 1,200 above-mentioned.  Now, to get out of this difficulty, and to temper those vast disagreements, I took the medium of 50 and 30 dying per annum, and pitched upon 40; and I also took the medium between 24 births and 23 burials, and 5 births for 4 burials, viz., allowing about 10 births for 9 burials; upon which supposition there must die 15 per annum out of the above-mentioned 600, and the births must be 16 and two-thirds, and the increase one and two-thirds, or five-thirds of a man, which number, compared with 1,800 thirds, or 600 men, gives 360 years for the time of doubling (including