MR. HIGHTON'S letter in NATURE is almost identical with his communication to the Chemical News. My answer is similar to that which I sent to the latter publication, viz., that the object of my paper in the Proceedings of the Literary and Philosophical Society was simply to place the theory of the electro-magnetic engine in a form which might prove useful to those who had not worked on the subject, and not in any respect to withdraw the reasonings in what Mr. Highton is good enough to term my “famous paper.” Mr. Highton handsomely acknowledged the justice of my note to the Chemical News in a letter addressed to me on the 28th ult.