324- 



Intelligence and Miscellaneous Arlicles. 



Aldeharan should be observed on every night when the planet is 

 observed. 



Those astronomers, who are possessed of good equatorial instru- 

 ments, may take repealed measures of the difference of declination 

 between the selected star and the planet on the same night: noting, 

 however, the times at which the observations v;ere made. 



The Ephemeris is extended from October 1 1th to December 25th, 

 for the purpose of including the stationary points of Mars, both in 

 right ascension and declination. 



The star (38) Arietis is to be found in Piazzi's catalogue: the 

 small stars (a) (jb) (c) are taken from Lalande's Histoire Celente, 

 page 33. The star (6) is the brightest, the most northerly, and the 

 second of two stars that are distant from each other about 2' in de- 

 clination j and between which Mars will pass on November 17th. 

 For this, and for two or three other proximate stars, the wire micro- 

 meter might be advantageously used in determining the difference of 

 declination. The places of the larger stars are taken from the cata- 

 logue of this Society, and the constants there given are used in the 

 reductions. 



The following are the assumed mean places, on January 1, 1832, 

 of the 10 stars selected for the comparisons j viz. 



Star. 



Mao 



(38) Arietis 

 65 



Mean M. 



8 



6 



9 

 6-7 



6 



8 



5 



7 

 67 



h m 



3 11 

 14 

 29 

 32 

 46 

 47 

 54 



4 8 

 9 



16 



12,37 

 44,87 

 15,55 

 38,01 

 56,77 

 20,25 

 46,12 

 26,98 

 32,03 

 21,26 



Mean D. i\'u tit. 



19 53 



20 12 



20 21 



19 9 



21 59 



20 49 



21 36 

 21 9 



20 43 



21 4 



50,48 

 9,87 

 45,62 

 23,82 

 18,00 

 44,88 

 55,94 

 43,42 

 44,60 

 53,84 



Other quantities, used in the computations, are the following 



Sun's horizontal parallax = 8",578 

 Mean semidiameter of Mars = 4 ,790 

 Constant of aberration = 493% 2 



Berlin, East of Paris =44" 

 of Greenwich = 53 



12%6 

 34,1 



*^* Mr. Henderson was also desirous that some stars should be 

 selected for observing the parallax of Mars in right ascension ; agree- 

 ably to the method pointed out by Lalande, in his Astronomie, vol. ii. 

 page 281 : since Mars will be favourably situated, at the ensuing 

 opposition, for such observations in the northern hemisphere. But 

 there are no stars, near the path of the planet at that time, of sufficient 

 magnitude for such purpose. 



