The Provincial Letters of Pascal drew attention first of all to the doctrine of probabilities, and John de Witt, a Dutchman, applied it to the subject of life annuities. He made a report to his Government, in which he used for the first time mathematical calculations in considering the probabilities of life. His report had no immediate effect. But he had sown the seed, and Leibnitz, who devoted much time to an investigation of the theory of chances--“c’est pour perfectionner l’art des arts, l’art de penser,” he explained--saved the essay from oblivion. But still there were no facts to go upon. It was the chance of the gaming table. How many times would Number 17 or Number 26 turn up on the Roulette board in a given evening, if neither of them had turned up, say, for a week before? What are the odds that “Trente et un et après” will be seen at the “Trente et quarante” table ten times in the course of an evening? It was with the limping guidance of such questions as these that the early forms of life assurance were arranged. If the grantor of the annuity were generous, that helped to a solution, but it was rare. If the annuitant himself were ignorant, that helped too, and this was more common. Until quite recently, the value of a life was accounted at seven years’ purchase. The Great Plague, however, which spread so much desolation, lent a little help in this direction. Such was the terror which the Plague inspired, so overwhelming was the fear of its return, that what we should now call the _morale_ of the race was shaken. The people of those days were as vague in their computations of numbers as in their spelling, and rumour would exaggerate into millions the deaths of thousands. In order, therefore, to reassure the public mind after the Great Plague, Bills of Mortality were issued by the various Parishes by Order of the Government. Up to the end of the 17th Century the appearance of these Bills was sporadic. But, with the beginning of the 18th Century, so useful had they already proved, they became a regular element in Parish life. They were made up on Wednesdays, published on Thursdays, and anyone who cared to pay 4s. a year could subscribe for a copy.