In about forty years he estimated that London had doubled itself (the number being, when he wrote, 670,000), and that the assessment of London was about one-eleventh of the whole territory: “Therefore, the people of the whole may be about 7,369,000; with which account that of the poll-money, hearth-money, and the bishops’ late numbering of the communicants, do pretty well agree.” This founder of the House of Lansdowne was a good deal puzzled by the growth of the metropolis. He thus accounts for it:--“The causes of its growth from 1642 to 1682 may be said to have been as follows: From 1642 to 1650, men came out of the country to London to shelter themselves from the outrages of the civil wars during that time. From 1650 to 1660, the royal party came to London for their more private and inexpensive living. From 1660 to 1670, the King’s friends and party came to receive his favours after his happy restoration. From 1670 to 1680, the frequency of plots and parliaments might bring extraordinary numbers to the city. But what reasons to assign for the like increase from 1604 to 1642, I know not, unless I should pick out some remarkable accident happening in each part of the said period, and make that to be the cause of this increase (as vulgar people make the cause of every man’s sickness to be what he did last eat); wherefore, rather than so say, I would rather quit what I have above said to be the cause of London’s increase from 1642 to 1682, and put the whole upon some natural and spontaneous benefits and advantages that men find by living in great more than in small societies: I shall, therefore, seek for the antecedent causes of this growth in the consequences of the like, considered in greater characters and proportions.” That the people are the life-blood of the kingdom, was Sir William’s fixed belief; and he said, that if the whole highlands of Scotland and the whole kingdom of Ireland were sunk in the ocean, so that the people were all saved and brought to the lowlands of Great Britain, the Sovereign and the subject in general would be enriched. The reader will smile when he hears that a great deal of useful information was embodied in Sir William Petty’s attempts to prove the following extraordinary points:-- 1st. That London doubles in 40 years, and all England in 360 years. 2nd. That there be in 1682 about 670,000 souls in London, and 7,400,000 in England and Wales; and about 20,000,000 of acres in land. 3rd. That the growth of London must stop of itself before the year 1800. 4th. That the world would be fully peopled within the next 2000 years.