256 Sir J. F. W. Herschel's Address to the 



with which observatories are furnished in these latter days 

 of astronomy, but also to the vigilance of observers. If I am 

 right in the principle, that discovery consists in the certain 

 knowledge of a new fact or a new truth, a knowledge grounded 

 on positive and tangible evidence, as distinct from bare sus- 

 picion or surmise that such a fact exists, or that such a pro- 

 position is true — if I am right in assigning as the moment of 

 discovery, that moment when the discoverer is first enabled 

 to say to himself, or to a bystander, " I am sure that such is 

 the fact, — and I am sure of it for such and such reasons,''^ 

 reasons subsequently acquiesced in as valid ones when the 

 discovery comes to be known and acknowledged — if, I say, I 

 am right in this principle (and I really can find no better), 

 then I think the discovery of this satellite must be considered 

 to date from the 19th of September last, and to have been 

 made simultaneously, putting diiFerence of longitude out of 

 the question, on both sides of the Atlantic. In speaking thus, 

 I desire, of course, to be understood as expressing only my 

 own private opinion, and in no way as backing that opinion 

 by the authority of the Society whose chair I for the moment 

 occupy. The Astronomical Society receives with equal joy 

 the intelligence of advances made in that science, from what- 

 ever quarter emanating, and accords the meed of its appro- 

 bation to diligence, devotion, and talent, with equal readi- 

 ness, wherever it finds them ; but declines entering into nice 

 questions of personal or national priority, and would, I am 

 sure, emphatically disavow the assumption of any title to lay 

 down authoritatively rules for the guidance of men's judg- 

 ments in such matters. The medal of this day is awarded 

 to Mr Lassell, not on account of this discovery alone, and as 

 such, but as taken in conjunction with the many other strik- 

 ing proofs he has afforded of successful devotion to our 

 science, both in the improvement and in the use of instru- 

 ments. And among the motives which have induced your 

 Council to place Professor Bond on the list of our associates 

 (I trust not long to be the only one of his countrymen by 

 whom that honour is enjoyed), though this discovery has had 

 its due and just weight, we have not been unheedful of his 

 general merits, both as an observer and as a theoretical astro- 



