[398] Phil. Mag., vol. ix. (4th series), p. 327.
[399] Spectra may be produced by diffraction as well as by refraction; but we are here only concerned with the subject in its simplest aspect.
[400] Astrologia Gallica (1661), p. 189.
[401] Pos. Phil., vol. i., pp. 114, 115 (Martineau's trans.).
[402] Proem Astronomiæ Pars Optica (1640), Op., t. ii.
[403] Pop. Vorl., pp. 14, 19, 408.
[404] Pos. Phil., p. 115.
CHAPTER II
SOLAR OBSERVATIONS AND THEORIES
The zeal with which solar studies have been pursued during the last half century has already gone far to redeem the neglect of the two preceding ones. Since Schwabe's discovery was published in 1851, observers have multiplied, new facts have been rapidly accumulated, and the previous comparative quiescence of thought on the great subject of the constitution of the sun, has been replaced by a bewildering variety of speculations, conjectures, and more or less justifiable inferences. It is satisfactory to find this novel impulse not only shared, but to a large extent guided, by our countrymen.