Leibnitz was in London in 1673, and from that time began to pay particular attention to mathematics. He was in correspondence with Newton, Oldenburg, and others, on questions connected with _infinite series_, and continued so more or less till 1684, when he published his first ideas on the Differential Calculus in the Leipzic Acts. But it is certain that Newton had been in possession of the same powers under a different name, from about 1665. The English philosopher drops various hints of his being in possession of a new method, but without explaining what it was, except in one letter of 1672, of which it was afterwards asserted that a copy had been forwarded to Leibnitz in 1676. Leibnitz published both on the Differential and Integral Calculus before the appearance of Newton’s Principia in 1687; and indeed before 1711, the era of the dispute, this new calculus had been so far extended by Leibnitz and the Bernoullis, that it began to assume a shape something like that in which it exists at the present day. In the first edition of the Principia, Newton expressly avows that he had, ten years before (namely, about 1677), informed Leibnitz that he had a method of drawing tangents, finding maxima and minima, &c.; and that Leibnitz had, in reply, actually communicated his own method, and that he (Newton) found it only differed from his own in symbols. This passage was, not very fairly, suppressed in the third edition of the Principia, which appeared in 1726, alter the dispute; and the space was filled up by an account of other matters. It was obvious that, on the supposition of plagiarism, it only gave Leibnitz a year to infer, from a hint or two, his method, notation, and results.