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The dark lines observed crossing a very clear solar spectrum at right angles to its length, first discovered by Wollaston, but named after Fraunhofer, a Bavarian optician who first thoroughly investigated them. They are caused by the absorption of portions of the rays emitted from the incandescent body of the sun in their passage through the gases and vapors, as those of iron, etc. This absorption takes place from the remarkable property possessed by gases and vapors of retaining those portions of a ray of light passing through them from an incandescent solid or liquid body, which they themselves would emit if incandescent. The discovery of these lines led to the invention and use of the spectroscope, to the science of spectroscopy, and to all the discoveries due to that wonderful science.

First examined by F., of Bavaria (died 1826). A great number of very narrow dark lines crossing the solar spectrum at right angles to its length. See Spectrum analysis.