The Planet Saturn. 143 



cally, according to the 3rd law of Kepler, for every point in 

 the breadth of the ring — and that it must differ, practically, 

 for every zone of the ring that has a separate existence ; 

 the width of each zone being probably determined by the 

 relative proportion of the forces of cohesion and gravity, 

 or, in other words, by its power of resisting the strain to which 

 it is subjected by a rotation, the uniformity of which must 

 necessarily be too rapid for its outer, too slow for its inner 

 edge. From this cause Laplace perceived that the ring must 

 be multiple ; and Pierce considers that it may be divided into 

 at least twenty annuli, each having a period of its own. 



The rotation of the dark ring, C, seems to be shown by the 

 varying colour of its ansae; but nothing definite has been 

 ascertained with respect to it. 



There are observations which seem to indicate that the 

 general plane of the rings is not always coincident with that of 

 the equator of the globe. We have already mentioned a want 

 of parallelism between the belts and ring observed by Iji and 

 De- Vico (Intellectual Observer, ix. 254) . The same was noticed 

 by Schwabe, 1828-29-30, when the ring-shadow and the belts 

 converged W., though not always equally.— 1833, Dec, he 

 saw the elliptic outline of the planet very obviously inclined to 

 the ring. — 1848, Sept. 30, shadow not exactly in direction of 

 equatorial belt. — Schmidt, the same on several nights, Sept., 

 proved by divided object-glass. 14, belts inclined to line of 

 satellites. — 1862, May 22, Secchi proved by measurement that 

 the black shadow was not parallel to the belts. Nothing 

 more, of course, could be inferred from a single observation of 

 this kind, than the probability of an oblique current in the 

 atmosphere of the ball ; but a little consideration will show, 

 that if the obliquity is maintained through a series of observa- 

 tions, when rotation has brought ail parts of the ball succes- 

 sively under the eye, it can only be explained by a temporary 

 deviation of the ring-plane from that of the equator — a very 

 curious feature, if it can be established. 



Another deviation from symmetry is implied in certain 

 appearances, which, if not illusory, may be ascribed either to 

 unequal curvature in the two hemispheres, or to an anomalous 

 position of the ring-plane, not dividing the ball exactly in half. 

 This construction might be put upon the observations of f|I and 

 Gruithuisen, about to be cited under the head of refraction ; 

 and the following may be added : Valz at the disappearance in 

 1833 saw 1ST. hemisphere much more considerable than S. — 

 1848, July 11, Bond II. saw ball most flattened at N. Pole. 

 — Aug. 29, it seems not symmetrical; flattest at N. Pole: 

 Bond I. — Sept. 9, Busch and Luther thought centre of ball 

 somewhat S. of that of ring. — Oct. 10, ring and shadow to 



