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