[25] The dark band produced when the sodium is placed within the lamp was observed on the same occasion. Then was also observed for the first time the magnificent blue band of lithium which the Bunsen's flame fails to bring out.
[26] New York: for more than a decade no such weather had been experienced. The snow was so deep that the ordinary means of locomotion were for a time suspended.
[27] 'Il faut reconnaître que parmi les peuples civilisés de nos jours il en est pen chez qui les hautes sciences aient fait moins de progrès qu'aux États-Unis, ou qui aient fourni moins de grands artistes, de poëtes illustres et de célèbres écrivains.' (De la Démocratie en Amérique, etc. tome ii. p. 36.)
[28] At these points the two rectangular vibrations into which the original polarized ray is resolved by the plates of gypsum, act upon each other like the two rectangular impulses imparted to our pendulum in Lecture IV., one being given when the pendulum is at the limit of its swing. Vibration is thus converted into rotation.
[29] The millimeter is about 1/25th of an inch.
INDEX.
Absorption, principles of, [199]
Airy, Sir George, severity and conclusiveness of his proofs, [209]
Alhazen, his inquiry respecting light, [14], [207]
Analyzer, polarizer and, [127]
——recompounding of the two systems of waves by the analyzer, [129]
Ångström, his paper on spectrum analysis, [202]
Arago, François, and Dr. Young, [50]
——his discoveries respecting light, [208]
Atomic polarity, [93-96]
Bacon, Roger, his inquiry respecting light, [14], [207]
Bartholinus, Erasmus, on Iceland spar, [112]
Bérard on polarization of heat, [180]
Blackness, meaning of, [32]
Boyle, Robert, his observations on colours, [65], [66]
——his remarks on fluorescence, [163], [164]
Bradley, James, discovers the aberration of light, [21], [22]
Brewster, Sir David, his chief objection to the undulatory theory of light, [47]
Brewster, Sir David, his discovery in biaxal crystals, [209]
Brougham, Mr. (afterwards Lord), ridicules Dr. T. Young's speculations, [50], [51]
Cæsium, discovery of, [193]
Calorescence, [174]
Clouds, actinic, [152-154]
——polarization of, [155]
Colours of thin plates, [64]
——Boyle's observations on, [65], [66]
——Hooke on the colours of thin plates, [67]
——of striated surfaces, [89], [90]
Comet of 1680, Newton's estimate of the temperature of, [168]
Crookes, Mr., his discovery of thallium, [193]
Crystals, action of, upon light, [98]
——built by polar force, [98]
——illustrations of crystallization, [99]
——architecture of, considered as an introduction to their action upon light, [98]
——bearings of crystallization upon optical phenomena, [106]
Crystals, rings surrounding the axes of, uniaxal and biaxal, [145]
Cuvier on ardour for knowledge, [220]
De Tocqueville, writings of, [215], [222], [223]
Descartes, his explanation of the rainbow, [24], [25]
——his ideas respecting the transmission of light, [43]
——his notion of light, [207]
Diamond, ignition of a, in oxygen, [169]
Diathermancy, [173]
Diffraction of light, phenomena of, [78]
——bands, [78], [79]
——explanation of, [80]
——colours produced by, [89]
Dollond, his experiments on achromatism, [28]
Draper, Dr., his investigation on heat, [172]
Drummond light, spectrum of, [195]
Earth, daily orbit of, [74]
Electric beam, heat of the, [168]
Electricity, discoveries in, [217], [218]
Emission theory of light, bases of the, [45]
——Newton espouses the theory, and the results of this espousal, [77]
Ether, Huyghens and Euler advocate and defend the conception of an, [48], [58]
——objected to by Newton, [58]
Euler espouses and defends the conception of an ether, [48], [58]
Eusebius on the natural philosophers of his time, [13]
Expansion by cold, [104]
Experiment, uses of, [3]
Eye, the, its imperfections, grown for ages towards perfection, [8]
——imperfect achromatism of the, [29], [note]
Faraday, Michael, his discovery of magneto-electricity, [218]
'Fits,' theory of, [73]
——its explanation of Newton's rings, [74]
——overthrow of the theory, [77]
Fizeau determines the velocity of light, [22]
Fluorescence, Stokes's discovery of, [161]
——the name, [174]
Forbes, Professor, polarizes and depolarizes heat, [180]
Foucault, determines the velocity of light, [22]
——his experiments on absorption, [197], [198]
Fraunhofer, his theoretical calculations respecting diffraction, [87]
——his lines, [193]
———their explanation by Kirchhoff, [193]
Fresnel, and Dr. Young, [50]
——his theoretical calculations respecting diffraction, [87]
——his mathematical abilities and immortal name, [210]
Goethe on fluorescence, [165]
Gravitation, origin of the notion of the attraction of, [92]
——strength of the theory of, [148]
Grimaldi, his discovery with respect to light, [56]
——Young's generalizations of, [56]
Hamilton, Sir William, of Dublin, his discovery of conical refraction, [209]
Heat, generation of, [6]
——Dr. Draper's investigation respecting, [171]
Helmholtz, his estimate of the genius of Young, [50]
——on the imperfect achromatism of the eye, [29], [note], [31]
——reveals the cause of green in the case of pigments, [37]
Henry, Professor Joseph, his invitation, [2]
Herschel, Sir John, his theoretical calculations respecting diffraction, [87]
——first notices and describes the fluorescence of sulphate of quinine, [165]
——his experiments on spectra, [201]
Herschel, Sir William, his experiments on the heat of the various colours of the solar spectrum, [171]
Hooke, Robert, on the colours of thin plates, [67]
——his remarks on the idea that light and heat are modes of motion, [68]
Horse-chestnut bark, fluorescence of, [165]
Huggins, Dr., his labours, [205]
Huyghens advocates the conception of ether, [48], [58]
——his celebrated principle, [83]
Huyghens on the double refraction of Iceland spar, [112]
Iceland spar, [109]
——double refraction caused by, [110]
——this double refraction first treated by Erasmus Bartholinus, [112]
——character of the beams emergent from, [114]
——tested by tourmaline, [116]
——Knoblauch's demonstration of the double refraction of, [185]
Ice-lens, combustion through, [167]
Imagination, scope of the, [42]
——note by Maclaurin on this point, 43 note
Janssen, M., on the rose-coloured solar prominences, [204]
Jupiter, Roemer's observations of the moons of, [20]
Jupiter's distance from the sun, [20]
Kepler, his investigations on the refraction of light, [14], [207]
Kirchhoff, Professor, his explanation of Fraunhofer's lines, [193]
——his precursors, [201]
——his claims, [203]
Knoblauch, his demonstration of the double refraction of heat of Iceland spar, [185]
Lactantius, on the natural philosophers of his time, [13]
Lamy, M., isolates thallium in ingots, [193]
Lesley, Professor, his invitation, [2]
Light familiar to the ancients, [5]
——generation of, [6], [7]
——spherical aberration of, [8]
——the rectilineal propagation of, and mode of producing it, [9]
——illustration showing that the angle of incidence is equal to the angle of reflection, [10], [11]
——sterility of the Middle Ages, [13]
——history of refraction, [14]
——demonstration of the fact of refraction, [14]
——partial and total reflection of, [16-20]
——velocity of, [20]
——Bradley's discovery of the aberration of light, [21], [22]
——principle of least time, [23]
——Descartes and the rainbow, [24]
——Newton's analysis of, [26], [27]
——synthesis of white light, [30]
——complementary colours, [31]
——yellow and blue lights produce white by their mixture, [31]
——what is the meaning of blackness? [32]
——analysis of the action of pigments upon, [33]
——absorption, [34]
——mixture of pigments contrasted with mixture of lights, [37]
——Wünsch on three simple colours in white light, [39] [note]
——Newton arrives at the emission theory, [45]
——Young's discovery of the undulatory theory, [49]
——illustrations of wave-motion, [58]
——interference of sound-waves, [58]
——velocity of, [60]
——principle of interference of waves of, [61]
——phenomena which first suggested the undulatory theory [62-69]
——soap-bubbles and their colours, [62-65]
——Newton's rings, [69-77]
——his espousal of the emission theory, and the results of this espousal, [77]
——transmitted light, [77]
——diffraction, [77], [89]
——origin of the notion of the attraction of gravitation, [92]
——polarity, how generated, [93]
——action of crystals upon, [98]
——refraction of, [106]
——elasticity and density, [108]
——double refraction, [109]
——chromatic phenomena produced by crystals in polarized, [121]
——the Nicol prism, [122]
——mechanism of, [125]
——vibrations, [125]
——composition and resolution of vibrations, [128]
——polarizer and analyzer, [127]
——recompounding the two systems of waves by the analyzer, [129]
——interference thus rendered possible, [131]
——chromatic phenomena produced by quartz, [139]
——magnetization, of, [141]
——rings surrounding the axes of crystals, [143]
——colour and polarization of sky, [149], [154]
——range of vision incommensurate with range of radiation, [159]
——effect of thallene on the spectrum, 162
——fluorescence, [162]
——transparency, [167]
——the ultra-red rays, [170]
——part played in Nature by these rays, [175]
——conversion of heat-rays into light-rays, [176]
——identity of radiant heat and, [177]
——polarization of heat, [180]
——principles of spectrum analysis, [189]
——spectra of incandescent vapours, [190]
——Fraunhofer's lines, and Kirchhoff's explanation of them, [193]
——solar chemistry, [195-197]
——demonstration of analogy between sound and, [198], [199]
——Kirchhoff and his precursors, [201]
——rose-coloured solar prominences, [204]
——results obtained by various workers, [205]
——summary and conclusion, [206]
——polarized, the spectra of, [227]
——measurement of the waves of, [234]
Lignum Nephriticum, fluorescence of, [164]
Lloyd, Dr., on polarization of heat, [180], [209]
Lockyer, Mr., on the rose-coloured solar prominences, [205]
Lycopodium, diffraction effects caused by the spores of, [88]
Magnetization of light, [141]
Malus, his discovery respecting reflected light through Iceland spar, [115]
——discovers the polarization of light by reflection, [208]
Masson, his essay on the bands of the induction spark, [202]
Melloni, on the polarization of heat, [180]
Metals, combustion of, [5], [6]
——spectrum analysis of, [190]
——spectrum bands proved by Bunsen and Kirchhoff to be characteristic of the vapour of, [192]
Mill, John Stuart, his scepticism regarding the undulatory theory, [149]
Miller, Dr., his drawings and descriptions of the spectra of various coloured flames, [201]
Morton, Professor, his discovery of thallene, [162]
Mother-of-pearl, colours of, [90]
Nature, a savage's interpretation of, [4]
Newton, Sir Isaac, his experiments on the composition of solar light, [26]
——his spectrum, [27]
——dispersion, [27]
——arrives at the emission theory of light, [45]
——his objection to the conception of an ether espoused and defended by Huyghens and Euler, [58]
——his optical career, [70]
——his rings, [69-77]
——his rings explained by the theory of 'fits,' [73]
——espouses the emission theory, [77]
——effects of this espousal, [77]
——his idea of gravitation, [92]
——his errors, [208]
Nicol prism, the, [122]
Ocean, colour of the, [35]
Œrsted, discovers the deflection of a magnetic needle by an electric current, [176]
Optics, science of, [4]
Pasteur referred to, [219]
Physical theories, origin of, [41-44]
Pigments, analysis of the action of, upon light, [33]
——mixture of, contrasted with mixture of lights, [37]
——Helmholtz reveals the cause of the green in the case of mixed blue and yellow pigments, [37]
——impurity of natural colours, [37]
Pitch of sound, [59]
Plücker, his drawings of spectra, [202]
Polariscope, stained glass in the, 130,[131]
——unannealed glass in the, [136]
Polarity, notion of, how generated, [93]
——atomic, [93-96]
——structural arrangements due to, [96]
——polarization of light, [112]
——tested by tourmaline, [116]
——and by reflection and refraction, [119]
——depolarization, [120]
Polarization of light, [112]
——circular, [140]
——sky-light, [149], [157]
——of artificial sky, [156]
——of radiant heat, [180]
Polarizer and analyzer, [127]
Poles of a magnet, [93]
Powell, Professor, on polarization of heat, [180]
Prism, the Nicol, [122]
Quartz, chromatic phenomena produced by, [139]
Radiant heat, [172]
——diathermancy, or perviousness to radiant heat, [173]
——conversion of heat-rays into light rays, [174]
——formation of invisible heat-images, [179]
——polarization of, [180]
——double refraction, [182]
——magnetization of, [184]
Rainbow, Descartes' explanation of the, [24]
Refraction, demonstration of, [14]
Refraction of light, [106]
——double, [109]
Reflection, partial and total, [16-20]
Respighi, results obtained by, [205]
Ritter, his discovery of the ultraviolet rays of the sun, [159]
Roemer, Olav, his observations of Jupiter's moons, [20]
——his determination of the velocity of light, [21]
Rubidium, discovery of, [193]
Rusting of iron, what it is, [5]
Schwerd, his observations respecting diffraction, [87]
Science, growth of, [176], [203]
Scoresby, Dr., succeeds in exploding gunpowder by the sun's rays conveyed by large lenses of ice, [167]
Secchi, results obtained by, [205]
Seebeck, Thomas, discovers thermo-electricity, [176]
——discovers the polarization of light by tourmaline, [208]
Selenite, experiments with thick and thin plates of, [124]
Silver spectrum, analysis of, [190], [191]
Sky-light, colour and polarization of, [149], [154]
——generation of artificial skies, [152]
Snell, Willebrord, his discovery, [14]
——his law, [15], [24]
Soap-bubbles and their colours, [63], [65]
Sound, early notions of the ancients respecting, [51]
——interference of waves of, [58]
——pitch of, [59]
——analogies of light and, [56]
——demonstration of analogy between, and light, [198], [199]
Sonorous vibrations, action of, [134]
Spectrum analysis, principles of, [189]
Spectra of incandescent vapours, [190]
——discontinuous, [191], [192]
——of polarized light, [227]
Spectrum bands proved by Bunsen and Kirchhoff to be characteristic of the vapour, [192]
——its capacity as an agent of discovery, [193]
——analysis of the sun and stars, [193]
Spottiswoode, Mr. William, [123], [227]
Stewart, Professor Balfour, [202]
Stokes, Professor, results of his examination of substances excited by the ultra-violet waves, [161]
——his discovery of fluorescence, [162]
——on fluorescence, [165]
——nearly anticipates Kirchhoff's discovery, [198], [202]
Striated surfaces, colours of, [89]
Sulphate of quinine first noticed and described by Sir John Herschel, [165]
Sun, chemistry of the, [195]
Sun, rose-coloured solar prominences, [204]
Talbot, Mr., his experiments, [201]
Tartaric acid, irregular crystallization of, and its effects, [131]
Thallene, its effect on the spectrum, [162]
Thallium, spectrum analysis of, [190], [191]
——discovery of, [193]
——isolated in ingots by M. Lamy, [193]
Theory, relation of, to experience, [91]
Thermo-electric pile, [176]
Thermo-electricity, discovery of, [176]
Tombeline, Mont, inverted image of, [19]
Tourmaline, polarization of light by means of, [112]
Transmitted light, reason for, [77]
Transparency, remarks on, [167]
Ultra-violet sun-rays, discovered by Ritter, [159]
——effects of, [160]
Ultra-red rays of the solar spectrum, [171]
——part played by the, [173]
Undulatory theory of light, bases of the, [47]
——Sir David Brewster's chief objection to the, [47]
Undulatory theory of light, Young's foundation of the, [49]
——phenomena which first suggested the, [62], [69]
——Mr. Mill's scepticism regarding the, [143]
——a demonstrated verity in the hands of Young, [210]
Vassenius describes the rose-coloured solar prominences in 1733, [204]
Vitellio, his skill and conscientiousness, [14]
——his investigations respecting light, [207]
Voltaic battery, use of, and its production of heat, [6], [7]
Water, deportment of, considered and explained, [105], [106]
Waves of water, [51]
——length of a wave, [52]
——interference of waves, [53-55]
Wertheim, M., his instrument for the determination of strains and pressures by the colours of polarized light, [134]
Wheatstone, Sir Charles, his analysis of the light of the electric spark, [202]
Whirlpool Rapids, illustration of the principle of the interference of waves at the, [55]
Willigen, Van der, his drawings of spectra, [202]
Wollaston, Dr., first observes lines in solar spectrum, [193]
——discovers the rings of Iceland spar, [209]
Woodbury, Mr., on the impurity of natural colours, [37]
Wünsch, Christian Ernst, on the three simple colours in white lights, [39] [note]
——his experiments, [39] [note]
Young, Dr. Thomas, his discovery of Egyptian hieroglyphics, [49]
——and the undulatory theory of light, [49]
——Helmholtz's estimate of him, [50]
——ridiculed by Brougham in the 'Edinburgh Review,' [50]
——generalizes Grimaldi's observation on light, [56], [57]
——photographs the ultra-violet rings of Newton, [160]