Page:Popular Science Monthly Volume 14.djvu/483

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tronomers to absurd and discordant conclusions in regard to the general movements and the stability of the rings.

With the resources which spectrum analysis has conferred on science, more advantages are to be expected from inquiries in regard to the exact nature of the matter of distant space; and the basis for opinions or conclusions in regard to the composition of celestial objects is more then usually favorable in the case of Saturn's bright rings. That they are not entirely liquid or gaseous is evident from their serrated edges shown in the observations of Trouvelot, and from the peculiar character of the inequalities observed during their disappearance by Lassell and other astronomers. And yet there are few solid substances which could endure the long course of turmoil and ruin without being reduced to powder, and thus rendered incapable of raising mountainous structures high enough to be visible from our earth. But if the great annular appendage were largely or wholly composed of water with a temperature near 32° Fahr., the readiness of the fluid to assume a frozen condition would be a remedy to the ceaseless work of destruction, and would give solidity enough to enable incipient satellites to rise to the height of more than one hundred miles before tumbling to pieces.

The range of temperature necessary for the continuance of such operations must be maintained chiefly by the thermal effects with which they are attended. Any large stock of primitive heat which (according to the more generally received opinions) the rings might have possessed at their origin, must have been long since wasted by radiation from their extensive surfaces. In that remote and frigid zone of our planetary domain, the rays of our sun are too feeble to mitigate the rigors of extreme cold; and the outer ring at least can obtain but little calorific relief from the great planet which it environs. But, from the incessant changes and convulsions in the restless fields of matter, heat is abundantly produced by the violent mechanical action which, in a ring of aqueous composition, would proceed in a manner calculated to give a uniformity of temperature. If such a half-frozen ocean were abnormally heated throughout much of its vast expanse, so that a large portion of its ice were liquefied, the water, on obtaining a preponderance, would perform its movements and fluctuations with less violence and loss of living force. The heat produced mechanically would be then less than the amount lost by radiation, and a return of cold would again give ice the ascendancy. Yet, as the temperature declined and the freezing extended, mechanical violence would again become more energetic; and heat would be more copiously developed by the collisions of icy blocks, and by the rise and fall of gigantic mountains.

Reasoning from the most reliable principles of physics, and guided by the light of recent discoveries, many eminent scientists have come to the very just conclusion that the movement in Saturn's rings must be attended with a loss of energy and a reduction in the size of the orbits