426 Prof. Powell on the Theory of the Aberration of Light. 



Again, the question was mixed up with the undulatory 

 theory. It seemed to be considered, at least by some, that a 

 lengthy and abstruse analytical investigation was now neces- 

 sary for anything like a complete explanation of what our 

 predecessors thought sufficiently made out by a short popular 

 illustration, or at most a simple geometrical construction. 



On some of these points the two very able mathematicians 

 who first started the question were themselves at issue : and 

 though some other points, at first involved in paradox and 

 mystery, were in some degree cleared up in the course of 

 the discussion, yet it cannot be denied that much still re- 

 mained which called for further elucidation ; and even yet it 

 cannot be said that the minds of the scientific world in ge- 

 neral have been brought to any agreement, or perhaps any 

 such clear and definite view of the real state of the case as to 

 be able to come to a final decision, or to render useless an 

 attempt to divest the question of some of the ambiguity and 

 difficulty in which it has been involved. 



I trust then it will not be deemed superfluous if, at a period 

 when the immediate controversy seems to have arrived at a 

 termination, I offer a few remarks which may assist in forming 

 a dispassionate judgement on the merits of the discussion ; 

 and in doing so I will premise that the chief point really at 

 issue seems to me to lie rather in the general nature of the 

 reasoning and the principles of philosophical logic involved, 

 than in those details to which the controversialists have more 

 immediately addressed themselves. 



I will then first advert to the question respecting the exist- 

 ing explanations of the facts, and afterwards to that respecting 

 theories of light. 



If we look to past times, from the date of the discovery of 

 aberration, there certainly appears to have prevailed some 

 little hesitation and difference of opinion as to the precise 

 mode of viewing and explaining it. 



Bradley himself seems to have felt an anxiety to dwell on 

 any circumstance capable of aiding the better conception of 

 his idea. Indeed, in the manner of his whole discussion we 

 may acknowledge the justice of a remark made by Prof. Ri- 

 gaud* on one portion of it, viz. that it "conveys the strong 

 impression of its being the result of an inquiry which was new 

 to the writer of it ; and shows an evident unwillingness to 

 omit anything which might bear upon the subject." Bradley's 

 original ideat (as is well known) was suggested by the chance 



* Prof. Rigaud's Memoir and Miscellaneous Works of Bradley, p. xxxiv. 

 Oxford, 1832. 

 f Rigaud's Memoir, p. xxx. Thomson's History of Royal Society, 346. 



