172 COSMOS. 



Cassiniin 1 675, but first accurately described by William Her 

 schel in 1789-1792. Since Short's time the outer has been 

 found to be streaked by numerous fine stripes, but these lines 

 or stripes have never been constant. Very recently, during 

 the latter months of the year 1850, a third very pale, feebly 

 luminous, and darker ring has been discovered between the 

 planet and the ring hitherto called the inner one. The dis- 

 covery was made nearly simultaneously by Bond, at Cam- 

 bridge (U. S.), on the 11th of November, by means of the 

 great refractor of Mertz with a fourteen-inch object-glass, and 

 by Dawes, near Maidstone, on the 25th of November. This 

 ring is separated from the second by a black line, and occu- 

 pies the third part of the space, between the second ring and 

 the body of the planet, which was formerly stated to be va- 

 cant, and through which Derham affirmed that he saw small 

 stars. 



The dimensions of the divided ring of Saturn have been de- 

 termined by Bessel and Struve. According to the latter, the 

 exterior diameter of the outer ring, at Saturn's mean distance, 

 appears to us under an angle 40"'09, equal to 153,200 geo- 

 graphical miles ; the interior diameter of the same ring, un- 

 der an angle of 35"-29, equal to 134,800 geographical miles. 

 For the exterior diameter of the inner (second) ring is ob- 

 tained 34"-47 ; for interior diameter of the same ring, 26"-67. 

 Struve fixes the space between the last-mentioned ring and 

 the surface of the planet at 4"-34. The entire breadth of the 

 first and second rings is 14,800 miles; the distance of the 

 rings from the surface of Saturn, about 20,000 ; the space 

 which separates the first from the second ring, and which 

 represents the black line of division seen by Dominique Cas- 

 sini, is only 1560 miles. The mass of the rings is, according 

 to Bessel, yj-j of the mass of Saturn. They present a few 

 elevations^ and irregularities, by means of which it has been 

 possible to determine approximatively their period of rotation 

 — exactly the same as that of the planet. The irregulari- 

 ties of form become perceptible on the disappearance of the 

 nngs, when one is generally lost sight of before the other. 



A very remarkable phenomenon was discovered by Schwabe, 

 at Dessau, in September, 1827 — the eccentric position of Sat- 

 urn. The ring is not concentric with the planet itself, but 



♦ Such mountain-like inequalities of surface have recently been again 

 noticed by Lassell in Liverpool, by means of a twenty-feet reflecting 

 telescope of his ow^n construction. — Report of the British Associationp 

 1850, p. 35. 



