THE OUTER PLANETS. 109 



noticed what Miss Clerke calls " a veil - like 

 extension of the lucid ring across half the dark 

 space separating it from the planet." No atten- 

 tion, however, was paid to Galle's observation. 

 On November 15, 1850, William Cranch Bond 

 (1789-1859), of the Harvard Observatory in 

 Massachusetts, discovered the same phenomenon 

 under its true form that of a dusky ring in- 

 terior to the more brilliant one. A fortnight 

 later, before the news of Bond's observation, 

 Dawes made the same discovery independently 

 at Wateringbury in England. This ring is 

 known as the dusky or "crape" ring. 



The discovery of the dusky ring brought to 

 the front the problem of the composition of the 

 ring- system. Laplace and Herschel considered 

 the rings to be solid, but this was denied in 1848 

 by Edouard Roche (1820-1880), who believed 

 them to consist of small particles, and in 1851 

 by G. P. Bond, who asserted that the variations 

 in the appearance of the system were sufficient 

 to negative the idea of their solidity ; but he 

 suggested that the rings were fluid. In 1857 

 the question was taken up by the Scottish 

 physicist, James Cleric - Maxwell (1831-1879), 

 who proved by mathematical calculation that 

 the rings could be neither solid nor fluid, but 

 were due to an aggregation of small particles, 



