This change of opinion was brought about by a series of circumstances over which he had no control. M. Nicolas Fatio de Duillier, a Swiss mathematician, resident in London, communicated to the Royal Society, in 1699, a paper on the line of quickest descent, which contains the following observations:—“Compelled by the evidence of facts, I hold Newton to have been the first inventor of this calculus, and the earliest by several years; and whether Leibnitz, the _second inventor_, has borrowed any thing from the other, I would prefer to my own judgment that of those who have seen the letters and other copies of the same manuscripts of Newton.” This imprudent remark, which by no means amounts to a charge of plagiarism, for Leibnitz is actually designated the _second inventor_, may be considered as showing that the English mathematicians had been cherishing suspicions unfavourable to Leibnitz, and there can be no doubt that a feeling had long prevailed that this mathematician either had, or might have seen, among the papers of Collins, the “_Analysis per Equationes, &c._,” which contained the principles of the fluxionary method. Leibnitz replied to the remark of Duillier with much good feeling. He appealed to the facts as exhibited in his correspondence with Oldenburg; he referred to Newton’s scholium as a testimony in his favour; and, without disputing or acknowledging the priority of Newton’s claim, he asserted his own right to the invention of the differential calculus. Fatio transmitted a reply to the Leipsic Acts; but the editor refused to insert it. The dispute, therefore, terminated, and the feelings of the contending parties continued for some time in a state of repose, though ready to break out on the slightest provocation.