Manuscript material relating to “Dynamical Theory” and of interest in connection with Chapter 6, Section 1, includes four pages in the Maxwell manuscript materials at the University Library, Cambridge (in Add. MSS 7655, V, c/8; c/11; and V, f/4), to which I shall make reference as follows: Three pages, apparently representing parts of an early draft of “Dynamical Theory,” and corresponding to pp. 559–61, 568, and 569, I shall denote “[DT, A],” “[DT, B],” and “[DT, C]”; a fourth, apparently representing part of a later draft of “Dynamical Theory,” and corresponding to p. 578, I shall denote “[DT, D].” The correspondences to the cited parts of “Dymanical Theory” are not in doubt; that A, B, and C are earlier is suggested by the numbering of the equations, which differs from the published version, whereas D agrees with the published version in numbering of equations. A and B are pages numbered 22 and 23 (evidently in Maxwell's hand), in V, c/8; C is a page numbered 24, in V, f/4, but helpfully identified in the handlist to Add. MSS 7655 as belonging with A and B. D is in V, c/11. Also of interest is the manuscript of “Dynamical Theory” that was submitted to the Royal Society and is preserved there – PT. 72.7 – to which I shall refer as “Dynamical Theory [MS].” (I am informed that much of this material will be published in Harman, ed., Letters and Papers of Maxwell, 2.)