The heavens above: a popular handbook of astronomy (1882)
Gillet, J. A. (Joseph Anthony), 1837-1908 · New York, Chicago, Potter, Ainsworth, & Co. · leaf 130
reciable density at themoon. (2) The absence of anatmosphere from the moonis also shown by the ab-sence of twiUght and ofdiffused daylight. Upon the earth, twilightcontinues until the sun iseighteen degrees below thehorizon ; that is, day andnight are separated by abelt twelve hundred miles in… … ■ -^ 112 ASTRONOMY. phere, we should notice a similar gradual transition from.the bright to the dark portions of her surface. Such, how-ever, is not the case. The boundary between the light anddarkness, though irregular, is sharply defined. Close to thisboundary the unillumined portion of the moon…
Astronomy
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