Page:Gods Glory in the Heavens.djvu/154

134 have minute dark parallel lines laid upon them, similar to the teeth of the comb. The chief merit of Kirchhoff and Bunsen lies in furnishing a complete explanation of the lines, and, at the same time, putting within our reach a new and universal analysis, applicable alike to celestial and terrestrial objects. A few grains of a gaseous substance can be detected in the remotest orb, as well as in the lamp upon our table.

If a solid body, such as platinum or charcoal, be raised to a white heat, the spectrum given by the prism will be complete, and perfectly continuous,— that is, all the colours will be found following one another in regular order; but they will not be cut up or striated by dark lines. This arises from the solidity of the body. If we saw only the naked incandescent ball of the sun, there would be no dark lines in the spectrum. How, then, are we to account for these lines?—simply by supposing that the sun is surrounded wdth a gaseous envelope, in which the incandescent particles of various substances are diffused. These substances intercept the rays of the incandescent body of the sun, and they intercept in such a way as to betray their nature. The climax of the discovery is, that the dark lines are the negative spectra of the gaseous substances in the sun's atmosphere. What is meant by negative is, that the bright bands in the spectrum of any substance, when diffused in the flame of a lamp, become