Astronomy for the use of schools and academies (1882) (14577969377)

Identifier: astronomyforuseo00gill (find matches)
Title: Astronomy for the use of schools and academies
Year: 1882 (1880s)
Authors: Gillet, J. A. (Joseph Anthony), 1837-1908 Rolfe, W. J. (William James), 1827-1910
Subjects: Astronomy
Publisher: New York : Potter, Ainsworth, & Co.
Contributing Library: The Library of Congress
Digitizing Sponsor: The Library of Congress



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Fig. 444. smaller ones, requiring a nine-inch telescope to be well seen.Besides these, the whole nebula is dotted with stars. ASTRONOMY. 383 In the winter of 1864-65 the spectrum of this nebulawas examined independently by Secchi and Huggins, whofound that it consisted of three bright lines, and henceconcluded that the nebula was composed, not of stars, butof glowing gas. The position of one of the lines was nearthat of a line of nitrogen, while another seemed to coin-cide with a hydrogen line. This would suggest that thenebula is a mixture of hydrogen and nitrogen gas; but ofthis we cannot be certain. 379. The Nebula in Argus.—There is a nebula (Fig.442) surroundingthe variable starEta Argus (355),which is remarka-ble as exhibitingvariations of bright-ness and of out-line. In many othernebulae, changeshave been suspect-ed ; but the indis-tinctness of outlinewhich characterizesmost of these ob-jects, and the very different aspect they present in telescopesof different powers, render