ON THEORIES Cflf THE CONSTITUTION OF SATURN'S RINGS. 287 



3rd. That this- loading must not only be very great, but very nicely 

 adjusted; because, if it were less than '81, or more than '83 of the whole, 

 the motion would be unstable. 



The mode in which such a system would be destroyed would be by the 

 collision between the planet and the inside of the ring. 



And it is evident that as no loading so enormous in comparison with the 

 ring actually exists, we are forced to consider the rings as fluid, or at least 

 not solid ; and we find that, in the case of a fluid ring, waves would be gene- 

 rated, which would break it up into portions, the number of which would 

 depend on the mass of Saturn directly, and on that of the ring inversely. 



It appears, therefore, that the only constitution possible for such a ring is 

 a series of disconnected masses, which may be fluid or s61id, and need not be 

 equal. The complicated internal motions of such a ring have been investigated, 

 and found to consist of four series of waves, which, when combined together, 

 will reproduce any form of original disturbance with all its consequences. The 

 motion of one of these waves was exhibited to the Society by means of a small 

 mechanical model made by Ramage of Aberdeen. 



This theory of the rings, being indicated by the mechanical theory as the 

 only one consistent with permanent motion, is further confirmed by recent obser- 

 vations on the inner obscure ring of Saturn. The limb of the planet is seen 

 through the substance of this ring, not refracted, as it would be through a 

 gas or fluid, but in its true position, as would be the case if the light passed 

 through interstices between the separate particles composing the ring. 



As the whole investigations are shortly to be published in a separate form, 

 the mathematical methods employed were not laid before the Society. 



