U9 



ON SATURN S RING. 



of their nodes would change in longer or shorter periods, 

 that would embrace several years. Their centres must> 

 equally oscillate round that of Saturn, and these circum- 

 stances together muft at length alter the apparent figure 

 of the rings as a whole. Their rotary motion does not 

 perceptibly change this figure, since it only replaces one 

 luminous part by another in the same plane. It is very 

 probable that the phenomena observed by Mr. Schroeter are 

 owing to variations of this kind. But if a point more or 

 less luminous than the rest adhere to the surface of one of 

 the separate rings, this point must move as rapidly as the 

 ring, and appear to change its position in a few hours. 

 We may presume with much probability, that it was a 

 point of this nature, which Herschel observed. 

 Appearances I would invite those observers, who have powerful tele- 



of Satura's scopes, to examine the appearance of Saturn's rinar with 

 ring deserve ... nn? • c^ ^ i 



farther exami- this view. 1 he variety ot these appearances greatly puz- 



nation, 2led geometricians and astronomers, till Huyghens found 



out their cause. The ring at first exhibited itself to Galileo 

 under the form of two small appendages adhering to the 

 body of Saturn: and Descartes, who had an unfortunate 

 propensity for explaining every thing in his Principles 

 of Philosophy, ascribes, in the third part of that work, the 

 stationary state of these supposed satellites to Saturn's al- 

 ways presenting the same face to the centre of his vortices. 

 We now know, that this state is repugnant to the law of 

 universal gravitation; and this reason would be sufficient, 

 to induce us to reject the explanation of Descartes, even if 

 we did not know the cause of these appearances. I do not 

 believe, that the ring is immovable, though this would be 

 less inconsistent with that grand law of nature; and I have 

 no doubt that farther obsei,-vations ; made with the view I 

 have just mentioned, will confine the results of the theory, 

 and the observations of Herschel. 



X. 



