138 ANNUAL REPORT SMITHSONIAN INSTITUTION, 194 



numerals, and usually prefixed by the letter J to identify them with 

 Jupiter. The four satellites discovered by Galileo were once named 

 but they are more commonly referred to as satellites I, II, III, and 

 IV than by their names, lo, Europa, Ganymede, and Callisto. The 

 satellites of Mars, Saturn, Uranus, and Neptune all have names, 

 although the name of Neptune's satellite, Triton, is not generally 

 used. When Barnard discovered the fifth satellite of Jupiter many 

 names were proposed for it but none was adopted. Barnard thought 

 that, since the names of the four bright satellites were so little used, 

 the new satellite should simply be called the Fifth Satellite. His 

 suggestion was followed and a similar custom has prevailed for all 

 those discovered since. This custom is very convenient and makes 

 it possible to foretell the name of the next satellite, should another 

 be discovered. It will be J XII. 



