[63] For an exact statement as to the relation between the directions of the lines of electric displacement and of the magnetic force, reference must be made to Professor Poynting’s paper, _Phil. Trans._, 1885, Part II., pp. 280, 281. The ideas are further developed in a series of articles in the _Electrician_, September, 1895. Reference should also be made to J. J. Thomson’s “Recent Researches in Electricity and Magnetism.” [64] Preface to Newton’s “Principia,” 2nd edition. [65] “Lezioni Accademiche” (Firenze, 1715), p. 25. [66] In his sentence μ stands for the refractive index. [67] Hertz’s papers have been translated into English by D. E. Jones, and are published under the title of _Electric Waves_. [68] Some of the consequences of this electrical resonance have been very strikingly shown by Professor Oliver Lodge. _See_ _Nature_, February 20th, 1890. [69] Hertz’s original results were no doubt affected by waves reflected from the walls and floor of the room in which he worked. An iron stove also, which was near his apparatus, may have had a disturbing influence; but for all this, it is to his genius and his brilliant achievements that the complete establishment of Maxwell’s theory is due. [70] The analogy does not consist only in the agreement between the more or less accurately measured velocities. The approximately equal velocity is only one element among many others. [71] For a very suggestive account of some possible theories, reference should be made to the presidential address of Professor W. M. Hicks to Section A of the British Association at Ipswich in 1895. INDEX. Aberdeen, Maxwell elected Professor at, 45; formation of University of, 51 Adams, W. G., succeeds Maxwell as Professor at King’s College, London, 58 Adams Prize, The, 48; gained by Maxwell, 50 Ampère, 155, 204 Ampère’s Law, 155, 156 _Annals of Philosophy_, Thomson’s, 112, 113 “Apostles,” club so called, 30, 89 Arago, 157 Aragonite, 200 Atom, article by Maxwell in _Encyclopædia Britannica_, 108 Avogadros’ Law, 117, 124 Bakerian Lecture, delivered by Maxwell, 58 Berkeley on the Theory of Vision, 38 Bernouilli, D., 113 Blackburne, Professor, 16 Blore, Rev. E. W., 67 Boehm, Bust of Maxwell by, 90 Boltzmann, Dr., 135, 137, 138, 144, 216 Boltzmann-Maxwell Theory, The, 140, 145 Boscovitch on Atoms, 108, 109 Boyle’s Law, 114, 117, 124 Brewster, Sir David, on Colour Sensation, 99 British Association, Maxwell and, 42,54; Lecture before, 80–82; Lines on President’s address, 83, 84 Butler, Dr. H. M., extract from sermon on Maxwell, 32–35 Bryan, G. H., 141, 143 Cambridge, Maxwell at, 28–46; Mathematical Tripos at, 60; Foundation of Professorship of Experimental Physics at, 66 _Cambridge and Dublin Mathematical Journal_, Papers by Maxwell in, 30 Campbell, Professor L., 9, 10, 12, 14, 22, 52, 57, 79 Cauchy’s Formula, 208