A text-book of general astronomy : for colleges and scientific schools (1888)
Young, Charles A. (Charles Augustus), 1834-1908 · Boston ; London : Ginn & Company · leaf 199
edge and narrower on the inner, and just beforethe spot disappears around the limb of the sun, the penumbra on theinner edge entirely disappears, — the appearance being preciselysuch as would be shown by a saucer-shaped cavity in the surfaceof a globe, the bottom of the cavity being painted black… … Fig. 98. — Sun Spots as Cavities. because the spots are so irregular in their form ; but by observingthe behavior of several hundred of them the truth comes out quiteclearly. Occasionally, when a very large spot passes off the sunslimb, the depression can be seen with the telescope. The fact was…
Astronomy
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