Aslionumical Sucietjj. 301 



presents tlie investigation of the formula; of computation. If/ de- 

 note the co-latitude of the place of observation, d the polar distance 

 of the pole-star, D that of the other star, a their (.iifference of right 

 ascensions, and t the time elapsed from the upper passage of the 

 pole-star to the moment of its being on the same vertical with the 

 other ; then the result of the investigation gives 



(TV • / . \ sin a, 



' '7 tan ; 



The values of 7 and <p being determined by the follov^ing equa- 

 tions : viz. 



(II; 7= sin(D-rf) 



(III) ... taniJ/ = 



sin d sin D cos i/- 



sin a a, .^(sin 2 D sin 'Z d\ 



sin (D — d) 

 sin a 



(IV) . . . sin a =-- 



^ ' ^ 7 tan (/ 



The author occupies a portion of his paper in tracing the limits 

 of error, and in pointing out in what cases the method is not strictly 

 true. 



Lastly : There was read a letter from M. Gambart to the Presi- 

 dent, dated Marseilles, 30th of December 1826. After adverting 

 to what may be supposed his temerity in anticipating the transit of 

 the comet seen in Bootes over the suns disc, on the 18th of Novem- 

 ber, he presents the elements of the parabolic orbit of another 

 comet, which are as below : viz 



Passage of the perihelion 1827. 34'-989 M.T. from midn'. 



Perihelion distance 0"4-.55 



Longitude of perihelion .... 34° 0' 50'' 



Longitude of the node 191 i^ 33 



Inclination 72 4 15 



Motion retrograde. 



M. Gambart exhibits a comparison of the results of these ele- 

 ments, and of his observations on the 27th, 28th, and 29th of De- 

 cember. He then adds a few remarks, which need not be recorded, 

 and congratulates himself and astronomers generally, upon the ex. 

 istence and success of the Astronomical Society of London. " What," 

 he asks, " may not be expected from so liberal an association ? Happy 

 the country where the love of science alone causes so many men of 

 enlightened minds to combine in such an object ! Happy, also, 

 those who dwell there !" 



The President read part of a private letter from M. Littrow, 

 Director of the Imperial Observatory at Vienna, stating that His 

 Majesty the Emperor of Austria has liberally authorized the pur- 

 chase, for that observatory, of a refractor, similar in all respects 

 to that made by Fraunhofer for the Observatory at Dorpat, and 

 which at the death of that excellent artist was leit (so he under- 

 stood the words " </cs noch iidrigeji") by him amongst his other 

 instruments undisposed of. 



nOYAL 



