Part I., one hundred and three names.

[41] Under the new regulations Physics was removed from the first part of the Tripos and formed, with the more advanced parts of Astronomy and Pure Mathematics, a part by itself, to which only the Wranglers were admitted. Thus the number of men encouraged to read Physics was very limited. This pernicious system was altered in the regulations at present in force, which came into action in 1892. Part I. of the Mathematical Tripos now contains Heat, Elementary Hydrodynamics and Sound, and the simpler parts of Electricity and Magnetism, and candidates for this examination do come to the laboratory, though not in very large numbers. The more advanced parts both of Mathematics and Physics are included in Part II.

[42] “Life of J. C. Maxwell,” p. 383.

[43] “Statique Expérimentale et Théorique des Liquides soumis aux seules Forces Moléculaires.” Par J. Plateau, Professeur à l’Université de Gaud.

[44] The “Red Lions” are a club formed by Members of the British Association to meet for relaxation after the graver labours of the day.

[45] “Leonum arida nutrix.”--_Horace._

[46] _v.r._, endless.

[47] “Life of J. C. Maxwell,” p. 394.

[48] “Life of J. C. Maxwell,” p. 404.

[49] In his “Hydrodynamics,” published in 1738, Daniel Bernouilli had discussed the constitution of a gas, and had proved from general considerations that the pressure, if it arose from the impact of a number of moving particles, must be proportional to the square of their velocity. (_See_ “Pogg. Ann.,” Bd. 107, 1859, p. 490.)

[50] The proof is as follows:--

If σ be the specific heat at constant volume, σ′ at constant pressure, and consider a unit of mass of gas at pressure p and volume v, let the volume increase by an amount dv, while the temperature dy.

Thus σ′dT = σdT + pdv

But pv = ⅔T/m

Hence p being constant,

pdv = ⅔ dT/m Therefore σ′ = σ + ⅔ 1/m

Now suppose an amount of heat, dH, is given to a single molecule and that its temperature is T. Its specific heat is σ, and

dH = σmdT But dH = βdT Therefore β = σm

Hence 1/m = σ/β

Thus σ′ = σ(1 + 2/(3β))

And σ′/σ = γ

Therefore γ = 1 + 2/(3β)

Or β = 2/(3(γ-1))

[51] Owing to an error of calculation the actual value obtained by Maxwell from these observations for the coefficient of viscosity is too great. More recent observers have found lower values than those given by him; the difference is thus explained.

[52] Studien über das Gleichgewicht der lebendigen Kraft zwischen bewegten materiellen Punkten Sitz d. k. Akad Wien, Band LVIII., 1868.

[53] Another supposition which might be made, and which is necessary in order to explain various actions observed in a compound gas under electric force, is that the parts of which a molecule is composed are continually changing. Thus a molecule of steam consists of two parts of hydrogen, one of oxygen, but a given molecule of oxygen is not always combined with the same two molecules of hydrogen; the particles are continually changed. In Maxwell’s paper an hypothesis of this kind is not dealt with.

[54] _Nature_, vol. 1., p. 152 (December 13th, 1894).

[55] See papers by Mr. Capstick, _Phil. Trans._, vols. 185–186.

[56] _Nature_, vol. x.

[57] An historical account of the development of the science of electricity will be found in the article “Electricity” in the _Encyclopædia Britannica_, ninth edition, by Professor Chrystal.

[58] Thomson (Lord Kelvin), “Papers on Electrostatics and Magnetism,” p. 15.

[59] J. J. Thomson, B.A., Report, 1885, pp. 109, 113, Report on Electrical Theories.

[60] Papers on “Electrostatics,” etc., p. 26.

[61] It is difficult to explain without analysis exactly what is measured by Maxwell’s Vector Potential. Its rate of change at any point of space measures the electromotive force at that point, so far as it is due to variations of the electric current in neighbouring conductors; the magnetic induction depends on the first differential coefficients of the components of the electro-tonic state; the electric current is related to their second differential coefficients in the same manner as the density of attracting matter is related to the potential it produces. In language which is now frequently used in mathematical physics, the electromotive force at a point due to magnetic induction is proportioned to the rate of change of the Vector Potential, the magnetic induction depends on the “curl” of the Vector Potential, while the electric current is measured by the “concentration” of the Vector Potential. From a knowledge of the Vector Potential these other quantities can be obtained by processes of differentiation.

[62] The 4 π is introduced because of the system of units usually employed to measure electrical quantities. If we adopted Mr. Oliver Heaviside’s “rational units,” it would disappear, as it does in (B).

[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

Cavendish, Henry, 73, 74; Works of, edited by Maxwell, 87, 154, 155

Cavendish Laboratory, built and presented to University of Cambridge, 73, 74

Cay, Miss Frances, 11

Cayley Portrait Fund, lines to Committee, 86

Challis, Professor, 49

Charles’ Law, 124

Chemical Society, Maxwell’s lecture before, 80–82

Clausius, on kinetic theory of gases, 119, 129, 130, 137

Clerks of Penicuik, The, 9, 10

Colour Perception, 94

Colour Sensation, Young on, 97, 98; Sir D. Brewster on, 99

Colours, paper by Maxwell, on, 40, 41; Helmholtz on, 99

Conductors and Insulators, Distinction between, 173

Cookson, Dr., 61

Corsock, Maxwell buried at, 90

Cotes, 202

Coulomb, 154

Curves, investigated by Maxwell, 19

Daniell’s cells, 77

Democritus, 108

Demonstrator of Physics, W. Garnett appointed, 75

Description of Oval Curves, first paper by Maxwell, 19

Devonshire, Duke of, Cavendish Laboratory built by, 73, 74; Letter of Thanks from University of Cambridge, 74

Dewar, Miss K. M., her marriage to Maxwell, 51

Dickinson, Lowes; Portrait of Maxwell by, 90

Diffusion of gases, 128

Discs for colour experiments, 99–101

Droop, H. R., 57

Dynamical Theory of the Electro-magnetic Field, Maxwell on, 57, 177

Dynamical Theory of Gases, Maxwell on, 58, 134

Edinburgh Academy, Maxwell’s school-life at, 13–18

Edinburgh, Royal Society of, Maxwell at meetings of, 18

Edinburgh, University of, Maxwell at, 22

Elastic Spheres, 144

Electric Displacement, 218, 219, 220

Electrical Theories, 94, 154, 155

Electricity and Magnetism, Maxwell’s book on, 59, 77, 79, 147, 155, 156, 176, 180–201; papers by Lord Kelvin on, 161–2; Application of Mathematical Analysis to, paper by G. Green, 158

Electricity, Modern Views of, by Professor Lodge, 177

Electro-kinetic Momentum, 221

Electro-magnetic Field, Dynamical Theory of, Maxwell on, 57, 177

Electro-magnetic Induction, 157

Electro-magnetic Theory of Light, 174

Electro-tonic State, 164

Electrostatic Induction, Faraday on, 159

_Encyclopædia Britannica_, articles by Maxwell in, 80, 108, 146

Ether, labile, 220

Experimental Physics, foundation of Professorship at Cambridge, 66; Election of Maxwell, 68

Faraday on electrical science, 157; on electrostatic induction, 159

Faraday’s Lines of Force, paper by Maxwell on, 44, 45, 148–153

Fawcett, W. M., architect of Cavendish Laboratory, 73

Fitzgerald, Professor, 177, 211

Forbes, Professor J. D., 18, 44, 54; friendship with Maxwell, 19; paper on Theory of Glaciers, 19; resigns Professorship at Edinburgh, 54

Galvani, 155

Garnett, W., appointed Demonstrator of Physics at Cambridge, 75; Life of Maxwell by, 94

Gases, Molecular theory of, 57, 108; Waterston on general theory of, 118; Clausius on, 119; diffusion of, 128

Gauss’ Theory, 156

Gay Lussac’s Law, 117

General Theory of Gases, Waterston on, 118; Clausius on, 119

Glenlair, home of Maxwell, 11, 23; laboratory at, 24; Maxwell’s life at, 58, 59; “Electricity and Magnetism” written at, 79

Gordon, J. E. H., 77, 78

Green, G., of Nottingham, paper on electricity and magnetism, 158; inventor of term “Potential,” 158

Hamilton, Sir W. R., 22

Hamilton’s Principle, 190

Heat, Text-book on, by Maxwell, 79

Helmholtz, 99, 156, 157, 175, 221

Henry, J., of Washington, on electro-magnetic induction, 157

Herapath on molecules, 112–116

Hertz, Heinrich, 204, 209–213

Hicks, W. M., 221

Hockin, C., 56

Holman, Professor, 133

Iceland Spar, 200

Insulators and Conductors, Distinction between, 173

Jenkin, Fleeming, 55, 56

Kelland, Professor, 22

Kelvin, Lord, 16, 142, 158, 159, 160, 168; on the Uniform Motion of Heat, 160; papers on Electricity and Magnetism, 161, 162

Kinetic energy, 124, 129, 136, 139, 191

King’s College, London, Maxwell elected Professor at, 54

Kohlrausch, 206

Kundt, 132

Labile Ether, 220

Laboratory at Glenlair, 24

Lagrange, 179

Lagrange’s Equations, 179, 190

Laplace, 155

Larmor, J., 141, 142

Lecher, 214

Lenz, 157

Litchfield, R. B., 46

Light, Electro-magnetic Theory of, 174; Waves of, 198, 199

Lodge, Professor, book on Modern Views of Electricity, 177

Lucretius, 108

Luminous Radiation, 221

Mathematical Tripos at Cambridge, subjects, 60; Maxwell an examiner for, 60, 80; experimental work in, 76

Matter and Motion, Maxwell on, 79

Maxwell, James Clerk, parentage and birthplace, 10, 11; childhood and school-days, 12–18; his mother’s death, 13; first lessons in geometry, 17; attends meetings of Royal Society of Edinburgh, 18; his first published paper, 19; friendship with Professor Forbes, 19; his polariscope, 20; enters the University of Edinburgh, 22; papers on Rolling Curves and Elastic Solids, 23; vacations at Glenlair, 23; laboratory at Glenlair, 24; undergraduate life at Cambridge, 28–36; elected scholar of Trinity, 29; illness at Lowestoft, 29; his friends at Cambridge, 30; Tripos and degree, 35–37; early researches, 38–44; paper on Colours, 40, 41; elected Fellow of Trinity, 43; Lecturer at Trinity, 43; Professor at Aberdeen, 45; his father’s death, 45; gains the Adams Prize, 50; marriage, 51; powers as teacher and lecturer, 52, 53; Professor at King’s College, London, 54; gains the Rumford Medal, 55; delivers Bakerian lecture, 58; resigns Professorship at King’s College, London, 58; life at Glenlair, 58, 59; visit to Italy, 59; Examiner for Mathematical Tripos, 60, 80; elected Professor of Experimental Physics at Cambridge, 68; Introductory Lecture, 68–72; Examiner for Natural Sciences Tripos, 79; articles in _Encyclopædia Britannica_, 80, 118, 146; papers in Nature, 80; lectures before British Association and Chemical Society, 80–82; humorous poems, 83–87; delivers Rede Lecture on the Telephone, 89; last illness and death, 89, 90; buried at Corsock, 90; bust and portrait, 90; religious views, 91, 92

Maxwell, John Clerk, 10, 11

Meyer, O. E., 133

Mill’s Logic, 38

Molecular Evolution, Lines on, 85

---- Physics, 94

---- Constitution of Bodies, Maxwell on, 146

---- Theory of Gases, 57, 108

Molecules, 109, 110; Herapath on, 112–116; lecture by Maxwell on, 146

Motion of Saturn’s Rings, subject for Adams Prize, 49

Munro, J. C., 40, 56, 68, 82

Natural Sciences Tripos, Maxwell Examiner for, 79

_Nature_, papers by Maxwell in, 80

Neumann, F. E., 156, 157

Newton’s Lunar Theory and Astronomy, 50

---- Principia, 202

Nicol, Wm., inventor of the polarising prism, 20

Niven, W. D., 27, 46, 51, 52, 60, 78, 87, 88, 93

Obermeyer, 134

Ohm’s Law, 77

Ophthalmoscope devised by Maxwell, 83

Oval Curves, Description of, Maxwell’s first paper, 19

Parkinson, Dr., 49

_Philosophical Magazine_, 56, 99, 115, 120, 133, 142

_Philosophical Transactions_, 56, 89, 132, 145

Physical Lines of Force, Maxwell on, 56, 158

Physics, Instruction in, at Cambridge, 61; Report of Syndicate on, 62–64; Demonstrator appointed, 75

Poincaré, 216

Poisson, 44; on distribution of electricity, 155

Polariscope, made by Maxwell, 20

“Potential,” term invented by G. Green, 158; the Vector, 165, 221

Poynting, Professor, 187–189

Puluj, 134

Quincke, 206

Radiation, Luminous, 221

Rarefied Gases, Stresses in, paper by Maxwell, 135, 145

Rayleigh, Lord, 67, 77

Rede Lecture on the Telephone, delivered by Maxwell, 89

Report on Electrical Theories, J. J. Thomson, 204

---- of Syndicate as to instruction in Physics at Cambridge, 62–64

Robertson, C. H., 28

Rolling Curves, Maxwell on, 23

Royal Society, The, Maxwell and, 55; Transactions of, 89

Rumford Medal gained by Maxwell, 55, 106

Sabine, Major-General, Vice-President of Royal Society, 106

Smith’s Prizes, 36

Standards of Electrical Resistance, Committee on, 55

Stewart, Balfour, 56, 125

Stresses in Rarefied Gases, Maxwell on, 135, 155

Tait, Professor P. G., 21, 26, 94

Tayler, Rev. C. B., 29

Telephone, Rede Lecture by Maxwell on, 89

Theory of Glaciers, Prof. Forbes on, 19

Thomson, J. J., 157, 208; Report on Electrical Theories, 205

Thomson’s _Annals of Philosophy_, 112, 113

Uniform Motion of Heat in Homogeneous Solid Bodies, paper by Lord Kelvin, 160, 161

University Commission, 47, 48, 62

Urr, Vale of, 11

Vector Potential, The, 165, 221

Viscosity of Gases, Experiments on, 58, 125, 132

Volta, Inventor of voltaic pile, 155

Waterston, J. J., on molecular theory of gases, 114, 115; on general theory of gases, 118

Waves of Light, 198, 199

Weber, W., 156, 206

Wedderburn, Mrs., 14

Wheatstone’s Bridge, 77

Williams, J., Archdeacon of Cardigan, 16

Willis, Professor, 44

Wilson, E., lines in memory of, 86, 87

Young, T., on colour sensation, 97, 98

PRINTED BY CASSELL & COMPANY, LIMITED, LA BELLE SAUVAGE, LONDON, E.C.

* * * * * *

Transcriber’s note:

Punctuation, hyphenation, and spelling were made consistent when a predominant preference was found in the original book; otherwise they were not changed.

Simple typographical errors were corrected; unpaired quotation marks were remedied when the change was obvious, and otherwise left unpaired.

Illustrations in this eBook have been positioned between paragraphs and outside quotations.

Footnotes, originally at the bottoms of pages, have been collected, renumbered, and placed just before the Index.

The Index was not checked for proper alphabetization or correct page references.

Some values in the original book are known today to be incorrect, but have not been changed here.

Page 133: The last equation on the page,

μ = μ₀ (1 + .00275 t - .00000034 t²)

was misprinted as

μ = μ₀ {1 + .00275 t .00000034 t²}.

It is shown here with corrections based on its cited source:

https://archive.org/details/s05philosophicalmag21londuoft/page/212

Page 144: “possibly of ether atoms bound with them” was printed that way, but “ether” may be a misprint for “other”.

Page 170: “hence at C, where they touch” was printed as “A”, but Figure 1 at that point is labelled “C”.