Contemporary with Graunt, and contributor to his attempts, was one of those strange, restless, speculative men whose love of money teaches them how to procure it, and whose desire to preserve it, by purchasing land, and leaving their heirs in possession, makes them the founders of noble English houses. This was Sir William Petty, who, in his “Essay on Political Arithmetick concerning the Growth of the City of London, with the Measures, Periods, Causes, and Consequences thereof,” made a further onward movement. The earlier portion of his life was passed in battling with the world. He was as much a votary of mathematics as of money, and was eminently successful in both. Although only the son of a Romney clothier, he was the founder of a house which has exercised an important influence on English political life--the House of Lansdowne. He began his career with nothing, and he closed it possessed of 15,000_l._ per annum. He lived at a time when social economy was but little regarded; and he published a volume which, however uncertain both in its data and its conclusions, was an attempt to apply arithmetic to the economics of life. It is both unphilosophical and unjust to say, “Petty was nothing of a politician or statesman, or even of a political economist. He was merely a political arithmetician; that is to say, he occupied himself with a consideration of the circumstances of society and of the forces and activity that pervaded it, only in so far as they could be stated and estimated numerically. His social science was little more than an affair of ciphering, a business of addition and subtraction.” It is from the figures of such men that our politicians form deductions, estimate consequences, frame laws, and create trade. It may be true that he was no seer, and that he was wrong in his prophetic capacity; but this is only another proof that statisticians rarely possess a large development of the imaginative faculty. That his work is worth perusal to all who are interested in his subject, although based on information which was rude and imperfect, we hope to show. In it he calculates that-- Between 1604 and 1605, there died in London 5,135 ” 1621 and 1622, ” 8,527 ” 1641 and 1642, ” 11,883 ” 1661 and 1662, ” 15,148 ” 1681 and 1682, ” 22,331.