OF AN EIGHTH SATELLITE OF SATURN. 279 



ing of Saturn's satellites, employ the proper names given to them 

 by Sir John Herschel in his Cape Observations, namely, Mimas, 

 Enceladus, Tethys, Dione, Rhea, Titan, and lapetus, beginning 

 with the closest, and proceeding in order of distance from their 

 primary. 



"On the 18th instant, while surveying the planet and looking 

 for lapetus, I observed two stars near the situation where I ex- 

 pected him to be. Not being certain which of these was he, I 

 made a careful drawing of their situation with respect to some 

 neighbouring fixed stars, of which the following is a copy. 



Titan. 



o • • • 



" On the 19th instant, I was surprised to find that both stars 

 had moved away from the fixed star «, as shown in the following 

 diagram, x still remaining in the line of the satellites interior to 



Titan 

 O • • 





* 



itself, while c had gone northward. A consideration of this ap- 

 pearance suggested the conviction that x must be a new satellite, 

 c being thus proved to be lapetus. I therefore immediately pro- 

 ceeded to take differences of A. R. between x and a and between 

 c and a, with a view to verify the conjecture, and found that in 

 2.6 hours x had moved westward 2^46, and that in 1.4 hours 

 c had also moved westward P.27, establishing the fact that 

 both stars were in motion. It is true that these differences do 

 not correspond precisely with the orbital motion of Saturn, but 

 I think they are not greater than can be well accounted for by 



