chel, 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

Wuensch, 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

End of the Project Gutenberg EBook of Six Lectures on Light, by John Tyndall

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