“I received what you wrote to me in Sir Isaac’s letter. I will set about the index in a day or two. As for the preface, I should be glad to know from Sir Isaac with what view he thinks proper to have it written. You know the book has been received abroad with some disadvantage, and the cause of it may be easily guessed at. The _Commercium Epistolicum_, lately published by order of the Royal Society, gives such indubitable proofs of Mr. Leibnitz’s want of candour, that I shall not scruple in the least to speak out the full truth of the matter, if it be thought convenient. There are some pieces of his looking this way which deserve a censure, as his _Tentamen de motuum cælestium causis_. If Sir Isaac is willing that something of this nature may be done, I should be glad if, while I am making the index, he would consider of it, and put down a few notes of what he thinks most material to be insisted on. This I say upon supposition that I write the preface myself. But I think it will be much more advisable that you, or he, or both of you should write it while you are in town. You may depend upon it I will own it, and defend it as well as I can, if hereafter there be occasion.—I am sir, &c.” We are not acquainted with the instructions which were given to Mr. Cotes in consequence of this application; but it appears from the preface itself, which contains a long and able summary of the Newtonian philosophy, that Sir Isaac had prohibited any personal reference to the conduct of Leibnitz. The general preface is dated 12th May, 1713, and in a subsidiary preface of only a few lines, dated March 28th, 1713, Sir Isaac mentions the leading alterations which had been made in this edition. The determination of the forces by which bodies may revolve in given orbits was simplified and enlarged. The theory of the resistance of fluids was more accurately investigated, and confirmed by new experiments. The theory of the moon and the precession of the equinoxes were more fully deduced from their principles; and the theory of comets was confirmed by several examples of their orbits more accurately computed.