Newcomb, Simon, 1835-1909 · New York, H. Holt & company · leaf 225
f the telescope, the spots are seen to be of very complex forms. The umbra is often extremely irregular in shape, and is sometimes crossed by bridges or ligaments of shining matter. The penumbra is composed of filaments of brighter and darker light, which are arranged in striae. The general aspect… … Fig. 59.— Umbra and Penumbra of Sun-spot. Galileo's observations show^ed them to belong to the sun itself, and to move uniformly across the solar disk from east to west. A spot just visible at the east limb of the sun on any one day travelled slow- ly across the disk for 12 or 14 days, when it…
Astronomy
Internet Archive · The Library of Congress · Public domain (published before 1931). Free to use for anything.
