362 POPULAR SCIENCE MONTHLY. 



less as the distance from the main ring increases, until the eye can 

 no longer detect their mass and the ring apparently ends. 



This explains why the outline of the planet can be seen through 

 the dark ring ; but if this fact is not enough, an observation made 

 on November 1,1 889, at the Lick Observatory will further confirm 

 the theory. This observation was of the outer satellite, which 

 was in such a position behind the planet as to pass through the 

 shadow of the rings and be eclipsed by it. Watching the satel- 

 lite, then, as it left the planet's shadow and slowly passed on into 

 the shadow of the rings, its light was seen to grow gradually 

 fainter as it passed through the shadow of the dark ring, but : did 

 not wholly disappear until the moon had entered the shadow of 

 the inner bright ring. This shows clearly that the dark ring is 

 partially transparent, but becomes more opaque as the bright ring 

 is approached. 



With regard to the satellites there is little to be said. There 

 are eight known at present, and there may be more, for they are 

 mostly quite small, as heavenly bodies go. Still, they form the 

 most numerous as well as the most extended family within the 

 sun's domain, for the outer one of all swings around Saturn at a 

 distance of two and a quarter millions of miles ten times as far 

 away as our own moon. This one, which is named Japetus, is just 

 about the size of the moon, and apparently shares the latter's 

 peculiar trait of always keeping one side toward its ruling planet. 

 This supposition is due to the fact that when on the western side 

 of Saturn Japetus is always very much brighter than when to the 

 eastward ; in fact, though easily seen with a telescope of moder- 

 ate power when brightest, it will almost entirely disappear when 

 faintest. It is difficult to explain the cause of such a marked 

 change, for one half of the satellite must be extremely bright and 

 the other half very much darker to produce it, but the fact re- 

 mains. 



Titan, as its name implies, is the largest of the group, and in 

 size is midway between Mars and Mercury in fact, it would make 

 a very respectable planet itself, for it is nearly half the diameter 

 of the earth. The other six are all considerably smaller than our 

 moon, and have been discovered in the order of their brightness, 

 their discovery keeping pace with the increase in the power of 

 telescopes, so it is quite possible that there may be others in this 

 already numerous family to be introduced later on. 



We spoke in the beginning of this article of destroying the 

 theories often put forth concerning the inhabitants and condi- 

 tions of life upon this far-off world. There are certain facts 

 and deductions, however, from which we can gain an idea 

 of some of the conditions which may prevail when Saturn has 

 finally reached a stage where life will be possible upon its sur- 



