108 SATURN. 



In years of looking for it, with a glass of more than 

 twelve inches aperture, I have seen it very few times. 



Enc@lad.us, the next in distance from Saturn, is a diffi- 

 cult object. 



Tethys can be seen with a Clark glass of three inches 

 aperture. It has more sparkle than the others. 



Rhea is whitey-blue in color, large, blurry, and shows 

 something of a disc. 



Titan could probably be seen with an opera-glass. It 

 is always seen when not behind the planet or in course 

 of transit. It is the Jupiter of the system — readily rec- 

 ognized by its orange color. 



The next satellite in the order of distance is Hyperion, 

 which I have never seen. It is too small for the tele- 

 scope at Vassar College. 



Japetus, the farthest of the satellites yet known, is 

 very peculiar in the changes of its light. It is very per- 

 ceptibly variable. Sweeping around at an enormous dis- 

 tance from Saturn, it is bright when on one side of the 

 planet and pale on the other side. 



The grouping of these little moons is very beautiful. 



At one time they will arrange themselves in a line ; 

 next, they curve above the ball ; and, anon, they cling- 

 around one of the ansse, as if the ring had dropped its 

 jewels. When the quickly-moving moons are seen near 

 together, changes of position are noticed in a few min- 

 utes. 



Although Jupiter is the only satellite spoken of as va- 

 riable in text-books, I have little doubt of the varia- 

 bility of Rhea and Dione, and a suspicion of changes in 

 Tethys. 



Dione is sometimes as bright as Tethys, and I have 

 seen the pale Rhea glowing like Titan. 



With the times and the rate of motion, and the angles 

 of inclination of the orbit, the problem of possible com- 

 binations must involve an infinite variety of groups. 



eo 



