i8o HERSCHEL AND HIS WORK 



width between the two parts. 1 The black disc or belt was 

 not in the middle of the ring's breadth. " It is a zone 

 of considerable breadth," which was always seen per- 

 manently in the same place. As it was not, what some 

 seem to have supposed, the shadow of a vast range of 

 mountains on the ring's surface, he resolved to wait 

 till the planet came into a position which would enable 

 him to see the stars through the black belt, if it really 

 were a division in the ring, a window, as it were, 

 through which he could look out into space beyond. 

 He does not appear to have been successful in this 

 quest, and it has not been done by others. That there 

 were two unequal rings, 2 separated by this black line, 

 he was satisfied. They were bright rings, but the 

 inner was the brighter of the two. Near the outer 

 edge of the outer ring, he observed and figured " a 

 black list," fainter than the dividing gulf. He did not 

 consider it a division in the outer ring, but it is now 

 a recognised feature, traceable all round. Herschel also 



1 The dimensions of Saturn and his rings are, according to Proctor 

 (Encyc. Brit., "Astronomy," p. 783) 



Diameter of the planet . . . 70,136 miles. 



Between planet and " crape " ring . 9,760 



Breadth of " crape " ring . . 8,660 



,, of inner bright ring ' .. . 17,605 



, , of division between bright rings 1,680 



,, of outer bright ring . . 9,625 



The diameter of the ring system is thus about 165,000 miles. Herschel 

 made it about (204,883) 205,000 miles in diameter. He believed that 

 the breadth of the ring is to the space between the ring and the planet 

 as 5 to 4 (Phil. Trans., 1806, p. 463). If the "crape" be left out of 

 account in measuring the ring, the proportion is about 5 to 3 '2 (Phil. 

 Trans, for 1792). He estimates the vacant space between the outer 

 and inner rings at nearly 2513 miles. 



2 In the proportion of 805 to 280, while the space between was 

 reckoned 115. 



