506 JAMES CLERK MAXWELL. 



The following extract shows how Maxwell mentally 

 realised every problem which he considered : 



When we have actually seen that great arch swung over the 

 equator of the planet without any visible connection, we cannot 

 bring our minds to rest. We cannot simply admit that such is 

 the case, and describe it as one of the observed facts in nature, 

 not admitting or requiring explanation. We must either explain 

 its motion on the principles of mechanics, or admit that, in the 

 Saturnian realms, there can be motion regulated by laws which 

 we are unable to explain. 



The investigation of the stability of the motion of a solid 

 ring, otherwise uniform but loaded with a heavy particle 

 upon its circumference, led to the conclusion that the mass 

 of the particle must be about four and a half times that of 

 the rest of the ring 



But this load, besides being inconsistent with the observed 

 appearance of the rings, must be far too artificially adjusted to 

 agree with the natural arrangements observed elsewhere, for a 

 very small error in excess or defect would render the ring again 

 unstable. 



We are therefore constrained to abandon the theory of the 

 solid ring, and to consider the case of a ring the parts of which 

 are not rigidly connected, as in the case of a ring of independent 

 satellites, or a fluid ring. 



There is now no danger of the whole ring, or any part of 

 it, being precipitated on the body of the planet. Every particle 

 of the ring is now to be regarded as an independent satellite of 

 Saturn, disturbed by the attraction of a ring of satellites at the 

 same mean distance from the planet, each of which, however, is 

 subject to slight displacements. The mutual action of the parts 

 of the ring will be so small compared with the attraction of the 

 planet that no part of the ring can ever cease to move round 

 Saturn as a satellite. 



But the question now before us is altogether different from 

 that relating to the solid ring. We have now to take account of 

 variations in the form and arrangement of the parts of the ring, 

 as well as its motion as a whole, and we have as yet no security 

 that these motions may not accumulate till the ring entirely loses 

 its original form, and collapses into one or more satellites circu- 

 lating round Saturn. In fact such a result is one of the leading 



