Astronomy for the use of schools and academies (1882) (14577533808)

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:
is to say, the moon must make more than a complete revo-lution in a synodical period. The greater length of the synodical period is also evidentfrom Fig. no. Trepresents the earth, and Z the moon. Thearrows indicate the direction in which each is moving. Whenthe earth is at T, and the moon at Z, the latter is in conjunc-tion. When the earth has reached T, and the moon Z, thelatter has made a sidereal revolution; but she will not bein conjunction again till the earth has reached T, and themoon L. 97. The Phases of the Moon. — When the new moonappears in the west, it has the form of a crescent, with its 94 ASTRONOMY. convex side towards the sun, and its horns towards the east.
Text Appearing After Image:
Fig in. As the moon advances towards quadrature, the crescentgrows thicker and thicker, till it becomes a half-circle at ASTRONOMY. 95 first quarter. When it passes quadrature, it begins to becomeconvex also on the side away from the sun, or gibbons inform. As it approaches opposition, it becomes more andmore nearly circular, until at opposition it is a full circle.From full moon to last quarter it is again gibbous, and atlast quarter a half-circle. From last quarter to new moonit is again crescent; but the horns of the crescent are nowturned towards the west. The successive phases of themoon are shown in Fig. in. 98. Cause of the Phases of the Moon.—Take a globe,half of which is colored white and the other half black insuch a way that the line which separates the white and blackportions shall be a great circle which passes through thepoles of the globe, and rotate the globe slowly, so as tobring the white half gradually into view. When the whitepart first comes into view, the* line