POETION OF THE COSMOS. THE PLANETS. 383 



Very recently, in the latter months of 185 0, Bond, at Cam- 

 bridge, U.S., on the llth of November, with the great 

 refractor of Merz having a 14-inch object-glass, and Dawes, 

 at Maidstone, in England, on the 25th of November, there- 

 fore almost simultaneously, discovered between the second, 

 (hitherto called the inner) ring, and the planet itself, a third 

 very faintly illuminated, darker ring. It is divided from 

 the second ring by a black line, and fills up a third part of 

 the space intervening between the second ring and the 

 planet, which has hitherto been supposed to be vacant, and 

 through which Derham thought he had seen small stars. 



The dimensions of the divided ring of Saturn have been 

 determined by Bessel and Struve. According to Strove, 

 the angle subtended by the external diameter of the outer- 

 most ring, at Saturn's mean distance, is 40"'09, equal to 

 38300 German, or 153200 English, geographical miles; 

 and the angle subtended by the internal diameter of the same 

 ring is 35"'29, equal to 33700 German, or 134800 English, 

 geographical miles. The external diameter of the second 

 ring has been determined at 34 "'4 7 ; and its internal 

 diameter at 26"*67. The interval which separates the last- 

 named ring from the surface of the planet is given by 

 Struve at 4"' 34. The entire breadth of the first and second 

 ring is 3700 German, or 14800 English, geographical 

 miles ; the distance of the ring from the surface of Saturn 

 is about 5000 German, or 20000 English, geographical 

 miles; the gap which separates the first and second rings, 

 and which is indicated by the black line of division seen by 

 Dominique Cassini, is only 390 German, or 1560 English, 

 geographical miles. The thickness of these rings is be- 

 lieved not to exceed 20 German, or 80 English, geogra- 



VOL. III. Y 



