Note 128 — Chapter VIII

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.