truth or falsehood of it, conceived the plan of the experiments carried out by M. Périer at the top and the foot of the Puy de Dôme. “It is true, sir,” he adds, “and I say it boldly, that this series of experiments was my own invention; and therefore I may say that the new knowledge thus acquired is entirely due to me.” To this letter M. Ribeyre made a satisfactory and touching reply. He expresses disapproval of the allusion of the Jesuit father, but as the discourse was otherwise free from offence, he was willing to attribute it to a “pardonable emulation among _savants_,” rather than to any intention of assailing Pascal. He makes, in short, the best excuse he can for the Jesuit, and hastens to assure Pascal that his reputation needed no justification:— “Your candour and your sincerity are too well known to admit any belief that you could do anything inconsistent with the virtuous profession apparent in all your actions and manner. I honour and revere your virtue more than your science; and as in both the one and the other you equal the most famous of the age, do not think it strange if, adding to the common esteem which all have of you, a friendship contracted many years ago with your father, I subscribe myself yours,” etc. But Pascal had to sustain suspicion and attack in a quarter more formidable than that of the Jesuit fathers at Montferrand. We have already spoken of the rather unhappy commencement of relations between him and Descartes. Farther on we get a more pleasant glimpse of these relations, in a letter from Jacqueline Pascal to Madame Périer, dated 25th September 1647, and apparently shortly after Pascal had retired to Paris, along with his younger sister, leaving their father for some time still at Rouen. This letter is so interesting, both in its bearing on the question which arose between Descartes and Pascal, and in itself, as giving the only account we have of personal intercourse between these two illustrious men, that we present it almost entire:—