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