[115] _Phosphorescence of the Diamond_: by M. Reiss (Revue Scientifique et Industrielle, vol. xxiii. p. 185).--“The diamond, phosphorescent by insulation, lost rapidly its phosphorescence when submitted to the action of the red rays of the solar spectrum. On the contrary, the blue rays are those which render the diamond the most luminous in the dark. It is probable that the phosphorescence produced by heat is equally diminished by the action of the red rays of the solar spectrum.” Giovanni Battista Beccaria published his experiments in 1769. See Priestley’s _History of Electricity_; and _On the Effects of Electricity upon Minerals which are Phosphorescent by Heat_; and _Further Experiments on the communication of Phosphorescence and Colour to bodies of Electricity_; by Thomas J. Pearsall.--Journal of the Royal Institution of Great Britain, Oct. 1830, Feb. 1831.--These two memoirs contain the most complete set of experiments on this subject which have yet been made; see _Placidus Heinrich_, _Phosphorescenz der Körper_, vol. iv.; Gmelin’s _Handbuch der Chemie_, part 1.;--_On the Phosphorescence of Minerals_, Brewster: Edinburgh Philosophical Journal, vol. i. p. 137.;--_The Aërial Noctiluca, or some New Phenomena, and a process of a factitious self shining substance_: Boyle’s Works, vol. iv. [116] _Des Effets produits sur les corps par les Rayons Solaires_: par M. Edmond Becquerel.--Annales de Chimie, vol. ix. p. 257. 1843. M. Becquerel has applied the term _phosphorogénique_ to those rays producing phosphorescence. CHAPTER VIII. ACTINISM--CHEMICAL RADIATIONS. The Sun-ray and its Powers--Darkening of Horn Silver--Niepce’s Discovery--Prismatic Spectrum--Refrangibility of Light, Heat, and Actinism--Daguerre’s Discovery--Photography--Chemical Effects produced by Solar Radiations--Absorption of Actinism--Phenomena of the Daguerreotype--Chemical Change produced upon all Bodies--Power of Matter to restore its Condition--Light protects from Chemical Change--Photographs taken in Darkness--Chemical Effects of Light on organized Forms--Chemical Effects of Solar Heat--Influence of Actinism on Electricity--Radiations in Darkness--Moser’s Discoveries, &c. Heat and light are derived from the sun, and we have attempted to show, not only that the phenomena of these two principles are different, but that they can scarcely, in the present condition of our knowledge, be regarded as modified manifestations of _one_ superior power. Associated with these two remarkable elements, others may exist in the solar rays. Electrical phenomena are certainly developed by both heat and light, and peculiar electric changes are produced by exposure to sunshine. Electricity may be merely _excited_ by the solar rays, or it may _flow_ like light from the sun. Chemical action may be only due to the disturbance of some diffused principle; or it may be directly owing to some agency which is radiated at once from the sun.