ON Saturn's RtvtOo I45 



resume its original state, or to depart from it: consequently 

 the slightest cause, such as the acti»n of a satellite, or of a 

 comet,: would be sufficient to precipitate the ellipsoid on 

 the planet. 



The indifferent equilibrium, which would take place for a does not hold 

 hollow sphere enveloping Saturn, does not exist for a circu- ^^^^ regard to 

 lar zone surrounding the planet. I have shown, in the book* 

 above quoted, that, if the two centres of a circular ring and 

 the planet did not coincide, they would repel each other, 

 and the ring would ultimately fall upon Saturn. The same 

 thing would take place, whatever the nature of the ring 

 might be, if it were without a rotary motion. But if we 

 conceive, that it is not similar in all its parts, so that its 

 centre of gravity does not coincide with the centre of its 

 figure ; and if we farther suppose, that it has a rapid rotary 

 motion in its own plane; its centre of gravity itself will turn 

 round the centre of Saturn, and gravitate toward this point 

 as a satellite, with this difference, that it can move in the 

 interior of the planet. Thus it will possess a stable motion. 



Accordingly the two conditions I have mentioned concur The ring 



to show, that the ring turns in its plane, on its own axis, therefore ha# 



and with rapidity. The time of its rotation must be nearly niotion."^" ^^^ 



that of the revolution of a satellite moving round Saturn at 



the same distance with the ring; and this time is about 10 



sexagesimal hours and a half. Mr, Herschel has confirmed 



this result by his observations. But how can we reconcile This apparent- 



these observations, and this theory, with the observations of 'y. ^"*^^"^^^^^"'' 

 . "^ . . with the stati- 



Mr. Schroeter, in which certain points of the ring, more lu- onary spots 



minous than the rest, have appeared a long time stationary? o^strvedby 

 1 • • 1 1 • 1 p .. • .Schroeter. 



1 conceive it may be done in the tollowing manner. 



The ring of Saturn is composed of several concentric Attempt to a« 

 rings. Powerful telescopes show two very distinctly, which count for 

 are confounded together by iradiation in weak telescopes. 

 It is very probable, that each of these rings is itself formed 

 of several, so that the whole may be considered as an assem- 

 blage of various concentric rings. Such would be the ag- 

 gregate of the orbits of the satellites of Jupiter, if each left 

 behind a permanent light in its path. The separate rings, 

 like these orbits, must be variously inclined to the equator 

 of the planet: and then their inclinations and the position 



Vol. XXV [I. Oct. 1810. L bf 



