Page:Popular Science Monthly Volume 14.djvu/482

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THE POPULAR SCIENCE MONTHLY.

PLANETARY RINGS AND NEW STARS.
By Professor DANIEL VAUGHAN.

THE study of celestial phenomena which represent changes of the greatest magnitude is an important source of intelligence respecting the course of creation and the diversified condition of the universe. In all well-directed efforts to explore the more profound secrets of space and of time, it is necessary to be guided by certain conspicuous marks which even unseen planets may leave behind them, on assuming new forms or in closing an inconceivably long term of existence. Within the solar domain there is, perhaps, no object which claims more interest or value for original inquiries in astronomy than Saturn's rings—whether they be regarded as presenting a picture of the first or the last stages of planetary life. With a wide deviation from the ordinary figure of worlds, they exhibit changes which are interesting on account of the vast scale on which they occur, and the light which they throw on the past and the future history of the solar system. In the absence of those restraints which secure much repose on the surface of our globe, the Saturnian girdle is abandoned to rage of the most violent commotions and becomes occasionally the seat of disturbances which, though transpiring at the distance of about 900,000,000 miles, are yet revealed by the telescope. The temporary divisions which have been so often observed in the rings are evidences of the terrific scenes of turmoil in this remote theatre of chaotic activity; as the opening and closing of visible chasms must be attended with physical convulsions immeasurably greater than any ever witnessed on our terrestrial abode.

From well-established principles of physical astronomy, it is easy to prove the impossibility of tranquil movements in a region so close to the great planet. Whether tenanted by innumerable solid masses or even by a vast expanse of fluid, the zones in which the Saturnian sway is so powerful must present a long-continued struggle for opposite ends. The matter spread over the wide annular fields is ever urged by its own attraction to collect together and form satellites, which are soon destroyed by the attractive disturbance of the primary, and have their parts scattered once more over a wide space. From the gravity due to their preponderating masses, the mountains or inequalities observed on the ring can not be prevented from growing at the expense of the matter along the zone in which they circulate; but with the increasing size the vast structures become at last incapable of sustaining the crushing strain in certain directions; so that a dilapidation and a dispersion of their materials become inevitable. It is in consequence of the ephemeral character of these mountains or embryonic satellites, that observations on them have sometimes led as-