362 Astronomical Society. 



mitted positions of Gambart's comet, deduced from observations 

 with the equatorial instrument of the Observatory of Padua, by 

 himself and his colleague, Dr. Conti. 



IV. A letter from Professor Bianchi, of Modena, containing ob- 

 servations of the right ascension of Venus. 



V. Occultations of the Stars and Planets observed at Dorpat, by 

 Professor Struve. 



Professor Struve observes, that " even with such a powerful 

 telescope as the Dorpat refractor, it is not easy to observe the 

 emersion of faint stars from the moon's bright limb. But the mi- 

 crometer, with the clock-work horary motion, affords a very satis- 

 factory method of measuring the distance of a star, after emersion 

 from the enlightened disc. These observations replace a lost emer- 

 sion, and have even this advantage over an emersion exactly ob- 

 served that they do not depend upon the inequalities of the edge 

 of the moon. Such micrometrical measures, both at immersion 

 and emersion, will be found in the accompanying occultations of 

 the Hyades. An accurate computation will show what degree of 

 accuracy may be expected from this mode of observing, and if there 

 be a constant error in the apparent diameter of the moon depending 

 upon the telescope employed. These measurements are, however, 

 very difficult, and, I should think, better adapted to Fraunhofer's 

 heliometer than to the wire micrometer." 



The telescopes were variously adjusted, upon close double stars, 

 upon Aldebaran, and upon the moon ; but though there were four or 

 more observers, in no instance was any projection seen. The dis- 

 appearances took place instantaneously, when the apparent centre 

 of the star entered upon the edge of the moon, and the re-appear- 

 ances were also instantaneous; neither was there any previous varia- 

 tion in the brilliance of the star. 



The observations consist of 



An occultation of Saturn by the moon... 16 Feb. 1826 



An occultation of a. Tauri 25 July 1829 Four observers. 



15 Oct. 



Occultations of a Tauri and the Hyades 9 Dec. Six observers. 



Occultations of the Hyades 28 Mar. 1830 



VI. Two notes by Mr. Lubbock, on the comet of Halley. 



In the first of these notes Mr. Lubbock has deduced the elements 

 of the orbit of this comet from Messier's observations, adopting the 

 value of the semiaxis major given by M. de Pontecoulant, and the 

 perturbations due to the principal planets computed by M. Da- 

 moiseau. The elements thus obtained satisfy, with considerable 

 exactness, Messier's observations from Jan. 22 to June 3, as is seen 

 from an accompanying table : and as they differ sensibly from those 

 stated by the author in his paper, vol. iv. p. 42, he wishes them to 

 be substituted in that place. 



Semiaxis major 18-0763 



Excentricity -9676 



Perihelion passage 1759, March 13-333 Mean time from Paris midnight. 



Inclination of orbit 17 36' 0" 



Longitude of the ascending node 53 45 \ Referred to the mean equi- 



Longitude of perihelion 303 3 20 j nox 1759. 



Adding 



