The Planet Saturn. . 55 



the conclusion, already adopted by some of the very early 

 observers, that, instead of the whole ring-system lying in an 

 uniform plane, there must be a slight degree of mutual incli- 

 nation in the surface of its subdivisions, and such an inclina* 

 tion as will occasion want of symmetry in its perspective 

 projection.* This would not be the result of mere inclination, 

 so long as the intersection of the planes, whatever might be 

 their number, passed through the centre of the planet, because 

 one half of each plane would be as much elevated as the other - 

 depressed on either side, like the ecliptic and equator in the 

 sky, and symmetry would not be interfered with. We must, 

 therefore, in order to explain the observed appearances, adopt 

 the idea of planes whose intersection does not pass through 

 the axis of Saturn — perhaps not even through any part of the 

 globe, or ring-system itself; and whose varying inclination — 

 for under the action of so many disturbing forces, their incli- 

 nations and nodes must vary — though symmetrical on either 

 side of their own intersections, or lines of nodes, would not be- 

 so on either side of the centre of the planet. Such an arrange- 

 ment would not involve any theoretical impossibility. It is* 

 not essential to the stable equilibrium of the whole system r 

 that the centres of gravity of the several rings should coincide 

 with that of the planet ; so long as this is the case with the 

 common centre of all, they would individually balance each 

 other on opposite sides of it. And even a want of coincidence 

 between the common centre of gravity of the rings, and that 

 of the planet, would not produce disintegration of the system, 

 provided each of those points revolved round an intermediate 

 one, the general centre of gravity of the whole. The mutual 

 attractions, however, of the rings, and the external influence 

 of the satellites, while not of necessity causing any permanent 

 derangement or ultimate collapse, would yet introduce a com- 

 plexity of balancing, the result of which would probably 

 transcend all human analysis, but which may possibly — more 

 cannot be said — produce the peculiar variations which the 

 foregoing details record, and which certainly are supported by 

 too great a mass of evidence to be treated as mere optical 

 deceptions. Theoretical inquiries, however, unless of the 

 most superficial and familiar character, lie wide of our present 

 object, which is simply to bring into one point of view the 

 most accessible data, that the student may, as the result of a 



* Bessel found by strict mathematical investigation that the times of the 

 disappearance and reappearance of the ring were incompatible with parallelism in 

 its opposite surfaces. But this, though harmonizing with the wedge-shaped form 

 recorded by Schwabe, is scarcely an adequate solution of many of the recorded 

 phenomena, and at any rate merely treats the system as a whole. Cassini II. 

 had anticipated this conclusion. 



