The heavens above: a popular handbook of astronomy (1882)
Gillet, J. A. (Joseph Anthony), 1837-1908 · New York, Chicago, Potter, Ainsworth, & Co. · leaf 233
also a faint continu-ous spectrum, in which have been observed a few of the moreprominent dark lines of the solar spectrum. This shows, that, while the corona may be in the maincomposed of glowing gas (as indicated by the bright linesof its spectrum), it also contains considerable matter in such… … Fig. 230. Each shadow is seen to be made up of a dark portioncalled the umbra, and of a lighter portion called thepenumbra. The light of the sun is completely excludedfrom the umbra, but only partially from the penumbra.The umbra is in the form of a cone, with its apex awayfrom the sun; though in…
Astronomy
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