[120] On a change produced by Exposure to the Beams of the Sun, in the properties of an elementary substance, by Professor Draper; On the changes which bodies undergo in the dark, by Robert Hunt: Report of the Thirteenth Meeting of the British Association, vol. xii,—Description of the Tithonometer, an instrument for measuring the chemical force of the Indigo-tithonic rays: by J. W. Draper, M.D.—Philosophical Magazine, Dec. 1843, vol. xxiii.
[121] For several illustrations of this remarkable phenomenon, see On the Action of the Rays of the Solar Spectrum on Vegetable Colours, and on some new Photographic Processes; by Sir John F. W. Herschel, Bart., K.H., F.R.S.—Phil. Trans. June, 1842, vol. cxxxiii.; On certain improvements on Photographic Processes described in a former communication, and on the Parathermic Rays of the Solar Spectrum; by Sir John F. W. Herschel, Bart., K.H., F.R.S., &c., in a letter addressed to S. Hunter Christie.—Phil. Trans. 1843, vol. cxxxiv.
[122] Sir J. F. W. Herschel; see also Researches on Light, by the Author.
[123] Attention has been directed to the protecting action of certain rays of the spectrum by Sir John Herschel and others. See the Eighteenth Report of the British Association for an experiment by the Author, in which it was proved that all the light rays protected photographic papers from chemical change, and, therefore, convincingly show that light and actinism were not similar powers.
[124] “Having noticed, one densely foggy day, that the disc of the sun was of a deep red colour, I directed my apparatus towards it. After ten seconds of exposure, I put the prepared plate in the mercury box, and I obtained a round image perfectly black;—the sun had produced no photogenic effect. In another experiment, I left the plate operating for twenty minutes; the sun had passed over a certain space of the plate, and there resulted an image seven or eight times the sun’s diameter in length; it was black throughout, so that it was evident, wherever the red disc of the sun had passed, not only was there a want of photogenic action, but the red rays had destroyed the effect produced previous to the sun’s passage. I repeated these experiments during several days successively, operating with a sun of different tints of red and yellow. These different tints produced nearly the same effect; wherever the sun had passed, there existed a black band.”—Mr. Claudet, On different properties of Solar Radiation, modified by coloured glass media, &c.: Phil. Trans. 1847. Part 2.
[125] “It may also be observed that the rays effective in destroying a given tint are, in a great many cases, those whose union produces a colour complementary to the tint destroyed, or at least one belonging to that class of colours to which such complementary tint may be referred. For example, yellows tending towards orange are destroyed with more energy by the blue rays; blue by the red, orange, and yellow rays; purples and pinks by yellow and green rays.”—Sir J. F. W. Herschel, On the action of the rays of the Solar Spectrum on Vegetable Colours: Phil. Trans., vol. cxxxiii. 1842.
[126] The following memoirs and works are necessary to a complete history of the inquiry:—Experiments and observations relating to various branches of natural philosophy, with a continuation of the observation on air: by Dr. Priestley. London, 1779. Mémoires Physico-chimiques, &c.: by J. Senebier. Expériences sur les végétaux, by De la Ville: Paris, 1782; and Phil. Trans. 1782. Observations sur les expériences de M. Ingenhousz: by De la Ville; Roz. obs. 23, 290. Expériences propres à développer les effets de la lumière sur certaines plantes: by Tessier; Mém. de l’Ac. des Sc. de Paris, 1783, p. 132; Licht. Mag. iv. 4, 146. Sur la vertu de l’eau impregnée d’air fixe pour en obtenir, par le moyen des plantes et de la lumière du soleil, de l’air déphlogistiqué: by Ingenhousz; Roz. obs. 24, 337. Expériences sur l’action de la lumière solaire dans la végétation: by Senebier; Genève et Paris, 1788, p. 61. Extrait des expériences de M. Senebier sur l’action de la lumière solaire dans la végétation: by Hasenfratz; Ann. Chim. iii. 2nd. ser. 266. Expériences relatives à l’influence de la lumière sur quelques végétaux: by De Candolle; Jour. de Ph. lii. 124: Voigt’s Mag. ii. 483; Gilb. Ann. xiii. 372; Mém. des Sav. Etr. i. 329. Recherches chimiques sur la végétation: by Saussure; Ann. Chim. l. 225; Jour. de Ph. lvii. p. 393; Gilb. Ann. xviii 208. Recherches sur la respiration des plantes exposées à la lumière du soleil; by Ruhland; Ann. Ch. Ph. iii. 411; Jour. de Ph. 1816. On the action of light upon plants, and of plants upon the atmosphere: by Dr. Daubeny; Phil. Trans. cxxvii January, 1836. On the action of yellow light in producing the green colour, and of indigo light on the movements of plants: by P. Gardner; Phil. Mag. xxiv.; Bibl. Univ. xlix. p. 376, and lii. p. 381. On the influence of light on plants: by R. Hunt; Phil. Mag. xxiv. p. 96; Bibl. Univ. xlix. p. 383; Athen. 1844. Note on the decomposition of carbonic acid by the leaves of plants, under the influence of yellow light: by Draper; Phil. Mag. xxv. p. 169. On the action of the yellow rays of light on vegetation: by Harkness; Phil. Mag. xxv. p. 339. Influence des rayons solaires sur la végétation: by Zantedeschi; Inst. No. 541, p. 157.
[127] Sir John Herschel’s Memoirs already referred to; and Reports on the influence of the Solar Rays on the growth of Plants, by Robert Hunt: Report of the British Association for the Advancement of Science, for 1847.
[128] Memoir on the Constitution of the Solar Spectrum, presented at the meeting of the Academy of Sciences, 1842, by M. Edmond Becquerel; Des effets produits sur les corps par les rayons solaires, par M. Edmond Becquerel, aide au Muséum d’Histoire Naturelle: Mémoire présenté à l’Académie des Sciences, le 23 Octobre, 1843.—“Dans le courant de ce mémoire, j’ai employé les noms de rayons lumineux, chimiques, et phosphorogéniques, pour désigner, dans chaque cas, la portion des rayons solaires qui agit pour produire, en particulier, les effets lumineux, chimiques, et phosphorogéniques; mais cela est sans préjudice de l’opinion que je viens d’émettre touchant l’existence d’un seul et même rayonnement.”
“My reply is this,” says M. Arago, in his paper entitled Considerations relative to the action of Light: “It is by no means proved that the photogenic modifications of sensitive substances result from the action of the solar light itself. The modifications are, perhaps, engendered by invisible radiations mixed with light properly so called, proceeding with it, and being similarly refracted. In this case, the experiment would prove not only that the spectrum formed by these invisible rays is not continuous, that there are solutions of continuity as in the visible spectrum, but also that in the two superposed spectra these solutions correspond exactly. This would be one of the most curious, one of the most strange results of physics.”—Taylor’s Scientific Memoirs.