702 TRANSACTIONS OF THE AMERICAN INSTITUTE. 



see them : whereas, in all other cases the meteoric or asteroidal 

 masses, though realh'- arranged in rings, are invisible, because, 

 instead of being aggregated as in Saturn's rings, they are formed 

 into more widely separated bodies, so small and dense that they 

 have not yet been discovered. What we call the zodiacal lights 

 undoubtedly proceed from several rings of asteroids, which diffef 

 from those between Jupiter and Mars, principally, in being smaller 

 and denser, so that they cannot be as easily seen. Some of the 

 asteroids which theory indicates, between Saturn and Ju^Diter, are 

 probably quite as large as Juno, and may yet be discovered. We 

 can now perceive why Saturn's system, (included within the orbit 

 of Japetus), is five millions of miles in diameter ; while that of 

 Jupiter, Cincluded within the orbit of Callisto), is only three mil- 

 lions. If the Saturnian system had shrunk so as to be twice its 

 present density, it would doubtless have occupied less space than 

 Jupiter's system does. 



The rings of the Jovian nebula were more dense and attractive 

 than those of the Saturnian ; and therefore purturbed one another 

 to such a degree that a large number were prevented from becom- 

 ing statellites, consequently the intervals between those that were 

 formed are very wide. 



One of the consequences of our theory is that the greater the 

 mass of a })rimary, the narrower the secondary rings were at a 

 given distance from the primary ; for the larger the primary the 

 greater must be the orbital velocities of the secondaries at given 

 distances ; and, of course, the narrower must have been the rings. 

 At the distance of one million of miles from Jupiter, the primitive 

 statellitic rings were much wider than those formed in the solar 

 system one million miles from the sun. Saturn's rings, at the 

 same distance, were still wider ; and the rings of our own terrestial 

 system, from the principal of which our moon was formed, was 

 the widest of all, Avhen the distance from the primar}^ is considered. 



Now let us compare two systems that are alike in everything, 

 except that in one the primary is many times the more massive. 

 What difference would that make in the secondaries ? The larger 

 the primary the greater, all else equal, must be the orbital veloci- 

 ties of the secondaries, and, consequently, the narrower the rings 

 formed within a given distance of the centre. The narrower the 

 rings the more they must have perturbed each other, and tended 

 to produce asteroids. This is the reason why the interval between 

 the primary and the first secondary is greater the larger the pri- 



