LIFE OF SIR ISAAC NEWTON. 49 " I. Mr. Leibnitz was in London in the beginning of the year 1673 ; and went thence in or about March, to Paris, where he kept a correspondence with Mr. Collins, by means of Mr. Olden burg, till about September, 1676, and then returned, by London and Amsterdam, to Hanover: and that Mr. Collins was very free in communicating to able mathematicians what he had received from Mr, Newton and Mr. Gregory. " II. That when Mr. Leibnitz was the first time in London, he contended for the invention of another differential method, properly so called ; and, notwithstanding he was shown by Dr. Pell that it was Newton?s method, persisted in maintaining it to be his own invention, by reason that he had found it by himself without knowing what Newton had done before, and had much improved it. And we find no mention of his having any other differential method than Newton's before his letter of the 21st of June, 1677, which was a year after a copy of Mr. Newton's letter of the 10th of December, 1672, had been sent to Paris to be communicated to him ; and above four years after Mr. Collins began to communicate that letter to his correspondents ; in which letter the method of fluxions was sufficiently described to any intelligent person. "III. That by Mr. Newton's letter, of the 13th of June, 1676 it appears that he had the method of fluxions above five years before the writing of that letter. And by his Analysis per ^Equationes numero Terminorum Infmitas, communicated by Dr. Barrow to Mr. Collins, in July, 1669, we find that he had invented the method before that time. "IV. That the differential method is one and the same with the method of fluxions, excepting the name and mode of notation ; Mr. Leibnitz calling those quantities differences which Mr. Newton calls moments, or fluxions ; and marking them with a letter d — a mark not used by Mr. Newton. " And, therefore, we take the proper question to be, not who invented this or that method, but, who was the first inventor of the method ? And we believe that those who have reputed Mr. Leibnitz the first inventor knew little or nothing of his correspond ence with Mr. Collins and Mr. Oldenburg long before, nor of Mr.