Royal Astronomical Society. 73 



suit tlie observations afforded, deducing the parallax separately from 

 the observations of right ascension, from the direct observations of 

 declination, and from the reflected observations of dechnation, and 

 this in respect of each of the two stars ; and though the resulting 

 parallax differed somewhat in the different cases, the general agree- 

 ment was satisfactory, and the amount much too large to be ascri- 

 bable to probable errors of observation. But notwithstanding the 

 corroboration which the results of these different modes of deduction 

 afforded each other, if the question of the parallax of this binary star 

 had been allowed to rest in the state in which it was placed in Mr. 

 Henderson's first paper, astronomers would probably have agreed in 

 thinking his investigation only went the length of establishing a 

 strong probability in favour of its existence. Mr. Main, after an 

 elaborate comparison of the result with the individual observations 

 from which it was deduced, observes, "For the present it must be 

 considered that the star well deserves a rigorous examination by all 

 the methods which the author himself has so well pointed out ; and 

 that, in the event of a parallax at all comparable with that assigned 

 by Mr. Henderson being found, he will deserve the merit of its dis- 

 covery, and the warmest thanks of astronomers, as an extender of 

 the knowledge we possess of our connexion with the sidereal sy- 

 stem." — Memoirs, vol. xii. p. 36. The result, however, was far too 

 curious to be allowed long to remain without an attempt being made 

 to confirm it. No sooner was Mr. Henderson's paper communicated 

 to Mr. Maclear, than that energetic astronomer undertook a series 

 of observations of the double altitudes of the two stars with the 

 mural circle,-Avith an express view to the question. They extend 

 over seventeen months, from March 26, 1839, to August 12, 1840 ; 

 and, as the mural circle at the Cape was changed shortly after their 

 commencement, they have the further advantage of having been 

 made, for the greater part, with a different instrument. These ob- 

 servations being transmitted to Mr. Henderson, he immediately un- 

 dertook to reduce them ; and, in an elaborate paper inserted in vol. 

 xii. of the Memoirs, he deduced the parallax for each of the two 

 stars both from the direct and reflected observations. The results 

 entirely confirmed his former deductions, but, as was to be expected 

 from the greater number of observations, they were more consistent. 

 The mean gave, as before, a parallax of about 1"; whence it is in- 

 ferred that this system, the nearest, perhaps, of the stellar bodies, 

 is separated from us by an interval exceeding 200,000 times the 

 distance of the sun from the earth. 



Looking to the history of this interesting subject — to the consist- 

 ent results given by the Dublin circle, which have been disproved 

 by other instruments — and considering that the present determina- 

 tion has as yet been only partially confirmed by the observations of 

 right ascension, the cautious astronomer will, perhaps, be inclined 

 to maintain some reserve until the star shall have been examined 

 with an instrument affording the means of exact micrometrical mea- 

 surement, or, at least, until a longer series of meridian observations 

 shall have been made ; for, as has been remarked by Sir John Her- 



