Image from page 98 of "A primary astronomy .." (1851)
Title: A primary astronomy ..
Authors: Mattison, Hiram, 1811-1868
Contributing Library: The Library of Congress
Digitizing Sponsor: The Library of Congress
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Text Appearing Before Image:
PRIMARY ASTRONOMY. 91 414. What other change has been noticed? For fifteen years the part of the rings toward usseems to be thrown up, while for the next fifteen it ap-pears to drop oelow the apparent center of the planet. TELESCOPIC PHASES OF THE RINGS OF SATURN. •« Jf X [The cause of these varying appearances of Saturn will be easily understood by ex-amining the next cut and the accompanying notes.] 415. How are these Rings affected as respects Light and Shade ? The Sun shines, alternately, fifteen years upon one side, and fifteen upon the other. SATURN AT DIFFERENT POINTS IN HIS ORBIT.
Text Appearing After Image:
[1. Here observe, first, that tlie axis of Saturn, like those of all the other planets,remains permanent, or parallel with itself; and as the rings are in the plane of hisequator, and at right angles with his axis, they also must remain parallel to them-selves, whatever position the planet may occupy in its orbit. 2. This being the case, it is obvious that while the planet is passing from A to E, theSim will shine upon the under or south side of the rings ; and while he passes from Eto A again, upon the upper or north side; and as it requires about 30 years for theplanet to traverse these two semicircles, it is plain that the alternate day and nighton the rings will be 15 years each. 3. A and E are the equinoctial end C and G the solstitial points in the orbit ofSaturn. At A and E the rings are edgewise toward the Sun, and also toward theEarth, provided Saturn is in opposition to the Sun. The rings of Saturn were invisi-ble as rings from the 22d of April, 1848, to the 19th of January,
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