Astronomy for the use of schools and academies (1882) (14577576200)

Identifier: astronomyforuseo00gill (find matches)
Title: Astronomy for the use of schools and academies
Year: 1882 (1880s)
Authors: Gillet, J. A. (Joseph Anthony), 1837-1908 Rolfe, W. J. (William James), 1827-1910
Subjects: Astronomy
Publisher: New York : Potter, Ainsworth, & Co.
Contributing Library: The Library of Congress
Digitizing Sponsor: The Library of Congress



Text Appearing Before Image:
Fig. 230. Each shadow is seen to be made up of a dark portioncalled the umbra, and of a lighter portion called thepenitmbra. The light of the sun is completely excludedfrom the umbra, but only partially from the penumbra.The umbra is in the form of a cone, with its apex awayfrom the sun; though in the case of the earths shadowit tapers very slowly. The penumbra surrounds the umbra, ASTRONOMY. 21 I and increases in size as we recede from the sun. The axisof the earths shadow lies in the plane of the ecliptic, whichin the figure is the surface of the page. As the moonsorbit is inclined five degrees to the plane of the ecliptic,the axis of the moons shadow will sometimes lie above,
Text Appearing After Image:
Fig. 231. ind sometimes below, the ecliptic. It will lie on the eclipticmly when the moon is at one of her nodes. 206. When there will be an Eclipse of the Moon. —The moon is eclipsed whenever it passes into the umbra/ the earths shadow. It will be seen from the figure thathe moon can pass into the shadow of the earth only whenhe is in opposition, or at full. Owing to the inclina-ion of the moons orbit to the ecliptic, the moon will pass 212 ASTRONOMY. either above or below the earths shadow when she is atfull, unless she happens to be near her node at this time:hence there is not an eclipse of the moon every month. When the moon simply passes into the penumbra of theearths shadow, the light of the moon is somewhat dimmed,