HERSCHEL THE DISCO VEBER. 21 



Jupiter. The globe of the planet, the rings 

 and the satellites, were favourite objects of 

 study at Bath and Slough. In 1794 he per- 

 ceived a spot on the surface of Saturn, and 

 made the first determination of the rotation of 

 the planet, which he fixed as 10 hours 16 

 minutes, a result confirmed by modern astron- 

 omers. The rings were subjected to the closest 

 scrutiny. Herschel believed them to be solid, 

 and he also considered them to revolve round 

 Saturn in about 10 hours. It appears that he 

 observed the famous " dusky ring," but supposed 

 it to be a belt on the surface of the planet. 

 He also studied Cassini's division in the ring, 

 ascertaining its reality. 



On completing his famous 40 -foot reflector, 

 Herschel, on August 28, 1789, turned it on 

 Saturn and its five known satellites. Near the 

 planet, and in the plane of the ring, was seen 

 another object, which Herschel believed to be 

 a sixth satellite. To settle the question, he 

 watched the planet for several hours to see if 

 the object would partake in the planet's motion. 

 Finding that it did, he announced it as a new 

 satellite, which he found to revolve round 

 Saturn in 1 day 8 hours. About three weeks 

 later, on September 17, Herschel discovered 

 another satellite yet closer to Saturn, revolving 



