PLANETARY RINGS AND NEW STARS. 471 



a small asteroid would become a satellite to Mars on passing through 

 the region over which his attraction is effective ; as the change would 

 depend mainly on the intervention of solar influence, and would require 

 rare conditions which the movements of many hundred asteroids could 

 furnish only during long periods of time. But it may be considered 

 certain that a moon obtained in this way must have had its primitive 

 path so very extensive, that its revolution occupied a term of several 

 months. Accordingly, if the asteroidal origin of the Martian moons be 

 adopted, their present condition must be indicative of greater devia- 

 tions from their primitive arrangement ; and it is evident that their 

 early large orbits could be reduced to the present small size only by a 

 resisting medium. This theory is, perhaps, not wholly proof against 

 all objections, but another which accounts better for the movements of 

 botli small secondaries in the plane of the equator of the planet, and 

 which I intend to set forth in a future article, involves also the neces- 

 sity of supposing the imperfect vacuity of celestial space. 



As, in traversing a rare medium, such small masses must lose more 

 velocity in one year than our globe would in many centuries under the 

 same circumstances, they afford the most available means for indicating 

 the slow alterations in the state of the universe. Jn the absence of 

 the diversified cases which are, no doubt, concealed from our knowledge 

 in distant solar systems, the small moons will serve as the means of 

 illustration of the ultimate effects of the slight but constant resistance 

 to celestial motion. It is evident that not many million years can 

 elapse before Phobos will have its orbit so far reduced that it will 

 sweep through the atmosphere of Mars, and then its career as a small 

 secondary world will close with a meteoric exhibition. A term of ex- 

 istence several hundred times longer must be ascribed to our moon, or 

 to the first satellite of Jupiter; but their end would be signalized by 

 a far greater display of meteoric effulgence. A secondary planet two 

 or three thousand miles in diameter, even if solid, would become unsta- 

 ble before coming in contact with its primary, and would undergo a 

 sudden dilapidation ; so that a numberless host of its fragments, scat- 

 tering into smaller orbits and plunging as meteors into the atmosphere 

 of the great central orb, would send forth a flood of brilliancy sufficient 

 to rival solar light, and to proclaim the great work of destruction to 

 the most distant parts of the universe. 



The paroxysmal manifestation of light which a planet could scarcely 

 fail to call forth in thus passing through its final stages of existence, 

 corresponds in every feature to the mysterious effulgence of temporary 

 stars. The accordance of the theory with facts appears more satisfac- 

 tory, in proportion as the problems involved in the inquiry are more ac- 

 curately solved with the aids of mathematics, and as new means of 

 observation reveal the true nature of these rare and transitory appari- 

 tions of stellar light in the skies. The theatre of one of the great 

 meteoric exhibitions in question may be the aerial envelope, not only 



