Electro astronomical atlas ... with explanatory notes, questions and answers (1874)
Spoor, J. W. (Joseph W.) · Albany, N.Y., Weed, Parsons and Company · leaf 31
the penumbraand umbra were mingled, and mixed up theirtints in varied proportions. [We owe to the Rev. W. R. Dawes the discov-ery that the umbra is but a darker kind of pen-umbra ; for under the best conditions of air andinstrument, he has found within some umbras amuch darker portion — which he… … Fig. 7.-WILLOW LEAF. Bun-spots, showing Umbra, Penumbra, and Luminous Bridges. (Nasmyth.)j that a ball of ignited quicklime, in a Drummondsoxyhydrogen lamp, which itself gives out an apparently near approach to sunlight, when pro-jected on the Sun appears as a Hack spot. Sothat the Sun-spots,…
Astronomy
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