File:Triumphs and wonders of the 19th century, the true mirror of a phenomenal era - Yerkes Telescope - page 95.jpg

Identifier: triumphswonderso01boyd (find matches)
Title: 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 ..
Year: 1899 (1890s)
Authors: Boyd, James Penny, 1836-1910
Subjects: Progress Inventions
Publisher: Philadelphia, Pa., A. J. Holman & Co
Contributing Library: The Library of Congress
Digitizing Sponsor: Sloan Foundation

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THE SPECTROSCOPE. The image formed by the light of any luminous body, after it has passed through a prism, is said to be the spectrum of that body. VIII. THE SPECTROSCOPE AND ITS TRIUMPHS. The spectroscope consists essentially of three tubes joined in the form of the letter Y, one of which is a small telescope, in the focus of which a narrow slit is placed to admit the ray of light that is to be examined; a prism, or a ruled grating that disperses the light, so as to form a spectrum; and a view telescope, with which to observe the various parts of the spectrum. By using a small telescope to view the spectrum of the sun, Fraunhofer, a German optician, in 1814, discovered that the whole length of the spectrum was crowded with dark lines, very narrow, indeed, but scattered all through the seven hues. He found that sunlight, whether taken directly or reflected

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YERKES TELESCOPE, UNIVERSITY OF CHICAGO. Largest in the World.
from clouds or from the moon or planets, invariably gave the same spectrum; but in no case did light from the stars give a spectrum of the same sort as that from the sun. Dr. Kirchhoff, of Heidelberg, in 1859, explained the origin of the dark lines, and showed that there are three kinds of spectra: first, that of an incandescent solid or liquid, which is always perfectly continuous, showing neither dark lines nor bright; second, the spectrum of a glowing gas, which consists of bright lines or bands separated by dark spaces. These lines are characteristic of the chemical elements that cause them; and so, from the composition of the bright lines in a spectrum, it is possible to tell their origin. Third, a spectrum crossed by dark lines; which occurs when an incandescent solid is viewed through absorbent vapors. In the solar eclipse of 1868, M. Janssen first noticed that the solar prominences gave a spectrum of the second kind, and thus proved that the prominences consist of glowing gas.

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