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in effect associates them in a real manner with the sidereal 
system. 
In fact, and in conclusion, that great astronomer was not 
bound, as so many of his modern followers have been, by his 
own earlier theories. As his researches continued, his views 
gradually changed. The process of change went on during the 
whole course of his career as an observer. He advanced steadily 
from truth to truth, and when at length the close of his labours 
approached, lie looked onwards, not backwards. He would 
have been the last to desire that astronomers should take even 
his latest and best theories as including all that they could 
desire or hope to know ; but it would have been even more 
painful to him to imagine that the views he held, when as yet 
his labours were but beginning, should be adopted by future 
astronomers in preference to those which were the fruits of his 
ripened experience. 
