100 
Proceedings of the 
it, and that the cohesion of the parts of so large a body can have no 
effect whatever on its motions, though it were made of the most 
rigid material known on earth. It is therefore necessary, in order 
to satisfy the demands of physical astronomy, to explain how a 
material system, presenting the appearance of Saturn’s Rings, can be 
maintained in permanent motion consistently with the laws of gravi- 
tation. The principal hypotheses which present themselves are 
these — 
I. The rings are solid bodies, regular or irregular. 
II. The rings are fluid bodies, liquid or gaseous. 
III. The rings are composed of loose materials. 
The results of mathematical investigation applied to the first case 
are, — 
ls£. That a uniform ring cannot have a permanent motion. 
2 d. That it is possible, by loading one side of the ring, to produce 
stability of motion, but that this loading must be very great com- 
pared with the whole mass of the rest of the ring, being as 82 to 18. 
3 d. 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 generated, 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 universally. 
It appears, therefore, that the only constitution possible for such 
a ring is a series of disconnected masses, which may be fluid or solid, 
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 
