he literally experimented upon Ireland himself, but that he examined by the best available means, the effects of such experiments as had been made there. The means turns out to be the use of political arithmetick, and that he considers the best means because it gives precise results. As we shall see, Petty's results were, at times, less accurate than precise, for his statistical materials were frequently inadequate and his employment of such as he had was sometimes injudicious. But the root of the matter was in him. The application of an appropriate method "not yet very usual" to a field of knowledge in which it was altogether new, justifies him in associating himself with the most eminent followers of the new philosophy, and even distinguishes him among his colleagues. It was by no misapprehension of his true significance that Narcissus Luttrell wrote in his diary simply, "Sir William Petty of the Royal Society is dead[1]."
The data of statistics do not now, nor did they ever present themselves spontaneously for scientific elaboration. In order therefore that legal provision should be made, and that money should be forthcoming, for their ascertainment, it was first necessary that the value of possible statistical deductions from accurate data should be demonstrated by the intelligent use of those sparse materials which lay ready to the student's hand. It is in this sense that we must judge the essays of Graunt and Petty, which pioneered the way of modern statistics, and so judged they will be found worthy of high praise. Graunt's book has the advantage of priority[2] and the greater advantage of dealing with a body of statistical data sufficiently extended and complete to warrant some confidence in deductions properly made from it. Petty 's materials, on the other hand, were highly defective. A few scattering bills from Paris and Dublin, haphazard returns from various tax offices, a guess here or there as to the area of a city[3]—the list is soon exhausted. Petty realized the incompleteness of his data, and repeatedly urged the institution of regular statistical returns[4]. He drew up a pattern for an improved bill of mortality for Dublin[5]. He even tried to secure the establishment of an Irish statistical office under his own management[6]. But it is not clear that anything of importance resulted from his efforts
