A high-school astronomy: in which the descriptive, physical, and practical are combined .. (1859)
Mattison, Hiram, 1811-1868 · New York, Mason brothers · leaf 128
umbra,till at length she comes in contact with the umbra, andthe real eclipse begins. 260. In order to measure and record the extent ofeclipses, the apparent diameters of the sun and moonare divided into twelve equal parts, called digits; andin predicting eclipses, astronomers usually state which…
Astronomy
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