[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. [129] The chemical evidence of this will be found in Sir John Herschel’s Memoir _On the Solar Spectrum_, and particularly as exemplified in the changes produced on the tartrate of silver. Similar influences are described as observed on a Daguerreotype plate, in a paper entitled _Experiments and Observations on Light which has permeated coloured media, and on the Chemical Action of the Solar Spectrum_; by Robert Hunt.--Philosophical Magazine, vol. xxvi. 1840.