Professor Stokes, of Cambridge, who made the preceding experiment, found that the chemical rays from a point in the solar spectrum produced, in a solution of the sulphate of quinine, light of a sky-blue colour, which emanates in all directions from the liquid, and that this blue fluorescent light contains, when analysed, all the rays of the spectrum; hence he inferred that the dispersive power or fluorescence had lowered the refrangibility of the chemical rays, so as to make them visible: and Sir David Brewster observes that the new spectrum, of all colours into which they were transformed, must possess the extraordinary property of being a luminous spectrum, either without chemical rays or full of them. The dispersion in the quinine solution is greatest near the surface, but the blue emanation proceeds from every part of the liquid; and Sir John Herschel, who discovered the fluorescent property in this liquid, and gave it the name of epipolic light, found that the remainder of the beam, when it issued from the solution, though not apparently different from the incident white light, is yet so much changed in passing through the liquid, that it is no longer capable of producing fluorescence, though still capable of common dispersion. The blue light from the solution of quinine, when examined, consisted of rays extending over a great part of the spectrum. By passing a sunbeam through a bluish kind of fluor-spar, Sir David Brewster perceived that the blue colour is not superficial, as it appears to be, but that some veins in the interior of the crystal disperse blue light, others pink, and even white light; in short, he met with fluorescence in such a variety of substances, that he concludes it may prevail more or less in the greater number of solids and liquids.