Triumphs and wonders of the 19th century, the true mirror of a phenomenal era, a volume of original, entertaining and instructive historic and descriptive writings, showing the many and marvellous achievements which distinguish an hundred years of material, intellectual, social and moral progress .. . iced that the spectrum of the suns light, whengreatly magnified, was not composed of colors gradually changing from one tothe other, but that the continuity of the colors was interrupted by dark , in 1814, had made a map of the solar spectrum, showing 576 ofthese dark lines. Fraun
Triumphs and wonders of the 19th century, the true mirror of a phenomenal era, a volume of original, entertaining and instructive historic and descriptive writings, showing the many and marvellous achievements which distinguish an hundred years of material, intellectual, social and moral progress .. . iced that the spectrum of the suns light, whengreatly magnified, was not composed of colors gradually changing from one tothe other, but that the continuity of the colors was interrupted by dark , in 1814, had made a map of the solar spectrum, showing 576 ofthese dark lines. Fraunhofer was entirely ignorant of the cause of these darklines, but when he had found them, not only in the light from the sun, butalso from the moon and the fixed stars, he properly concluded that they weredue to something entirely independent of the earth. It remained for Bunsen and Kirchoff, in 1860, to point out the fact thatthese dark lines were characteristic of certain chemical elements existing inthe sun and its photosphere,, and this fact is the foundation of spectrum ana-lysis. The broad black band in the suns spectrum, called by Fraunhofer D,corresponded exactly in position and in width with the yellow band producedby a flame containing incandescent sodium. There was no doubt whatever,. WILLIAM CRItOKE THE CENTURYS PROGRESS IN CHEMISTRY 201 therefore, that the two phenomena were due to the same cause; but why inthe one case should the band be black and in the other yellow . This ques-tion was answered by the discovery of the fact that a ray of light colored byincandescent sodium, passing through a luminous atmosphere of the samemetal, would lose by absorption all of its yellow color, and would display ablack band where before the yellow color existed. Based upon this observation, the development of spectrum analysis wentforward with amazing rapidity. The hundreds of lines in the suns spectrumwere found to occupy exactly the position of luminous lini s in the spectra ofv
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