Astronomy for the use of schools and academies (1882) (14577632089)

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. 240. enough to reach the earth. Sometimes the point of thisshadow falls short of the earths surface, as shown inFig. 239, and sometimes it falls upon the earth, as shownin Fig. 240, according to the varying distance of the sunand moon from the earth. The diameter of the umbra atthe surface of the earth is seldom more than a hundred ASTRONOMY. 219 miles: hence the belt of a total eclipse is, on the average,not more than a hundred miles wide; and a total eclipseseldom lasts more than five or six minutes, and sometimesonly a few seconds. Owing, however, to the rotation ofthe earth, the umbra of the moons shadow may pass overa long reach of the earths surface. Fig. 241 shows the

Text Appearing After Image:

Fig. 241. track of the umbra of the moons shadow over the earthin the total eclipse of i860. Fig. 242 shows the track of the total eclipse of 1871across India and the adjacent seas. In a partial eclipse of the sun, more or less of one sideof the suns disk is usually concealed, as shown in Fig. 243.Occasionally, however, the centre of the suns disk is cov-ered, leaving a bright ring around the margin, as shown inFig. 244. Such an eclipse is called an annular eclipse. 220 ASTRONOMY, An eclipse can be annular only when the cone of themoons shadow is too short to reach the earth, and then

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1882

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