Royal Astronomical Society. 988 



servations, like those of double stars, requiring little calculation, but 

 demanding peremptorily the most complete devotion of time and 

 energies when favourable states of the air occur, are likely alvi^ays to 

 be better carried on by private observers than by official astronomers. 

 I might state, that the regular observer, when wearied with five hours' 

 calculation in the forenoon, is not likely to seize upon that pj-ecioua 

 eky which sometimes suddenly presents itself in the evening, and to 

 continue his observations till dawning day terminates them. I might, 

 on the other hand, explain that private observers can seldom under- 

 take the masses of calculation which are incidental to meridional ob- 

 servations. But I shall remark no further on this than to observe 

 that, in the instance of the double-star observations before us, as well 

 as in many of the others, discretion has been shown in the selection 

 of the subject as well as perseverance and skill in the pursuit of it. 



Gentlemen, the position of the person by whom this work has 

 been executed is thus far important, that it is necessary for us to di- 

 stinguish between the work executed in the discharge of official duty, 

 and that which is presented by the gratuitous labour and expense of 

 a private mdividuai upon whom we have no claim of any kind. The 

 former circumstance may frequently prevent us from even taking into 

 consideration the merits of some important works ; the latter will 

 render similar works admissible for our judgement as to the propriety 

 of awarding to them our Medal. But when I have said admissible 

 for our judgement, I have said all. No claim whatever is established 

 by this gratuitous character of the work. The claim must be founded 

 only upon the value of the work with reference to the present 

 wants of science ; and to this point I shall now advert. 



It has happened, gentlemen, that I have twice had the honour to 

 deliver addresses from this chair, in which allusion has necessarily 

 been made to the nature of the nebulae, and of those apparently ne- 

 buloid bodies, the comets. I have endeavoured to explain my idea, 

 that it is in the examination of these that the cosmogonic niiysteries 

 of the world are to be read on the ]arge scale, as in geology on the 

 small scale. The investigation of the motion of double stars appears 

 to me likely to give us an insight into laws equally grand, but of 

 very different character. It is here alone that we can see the me^- 

 chanics of the universe on a grand scale. The radius of the orbit of 

 Uranus is small in comparison with the distance of the two stars of 

 61 Cygni, and probably very small in comparison with the distance 

 between the components of some binary stars whose parallaxes have 

 not yet been ascertained. The law of gravitation seems to be failing 

 even at the distance of Uranus. May it not, perhaps, fail more com* 

 pletely, or may not a different law almost completely prevail over it, 

 at distances like those of the double stars ? Whether this question 

 is to be answered affirmatively or negatively, and whatever may be 

 the modification which the law may require, this appears certain, 

 that it is only in the observation of double stars that we can find an 

 answer to the question. 



If now we inquire what is the quality of our observations upon 

 which the correctness of our answer will mainly depend, we find th^t 



