20 
SEE. 
of the satellite’s orbit is shown to be 531.75 years. These 
elements, deduced entirely from theoretical considerations, 
are the more satisfactory as affording explanations of phe¬ 
nomena which otherwise would be quite obscure. 
If it appears that theoretical astronomy has made no great 
leaps during the past year, it may be held that it has at least 
kept pace with the steady progress characteristic of this rec¬ 
ondite branch of science during the whole of the present 
century. 
