Royal Astronomical Society. 569 



sisting of two individuals, the one of a high and somewhat brownish 

 orange, the other of a fine yellow colour, and each of which I con- 

 sider fairly entitled to be classed in the first magnitude*. Their 

 distance is at present about 15" asunder, but it is rapidly diminish- 

 ing, and in no great lapse of time they will probably occult one 

 another, their angular motion being comparatively small. Their 

 apparent distance was formerly much greater : how much we can- 

 not say for want of observations, but probably the major axis of 

 their mutual orbit is little short of a minute of space. They, there- 

 fore, afford strong indications of being very near our system. Add 

 to which their proper motion is very considerable, and participated 

 in by both, which proves their connexion as a binary system ; and 

 an additional presumption in favour of their proximity may be drawn 

 from their situation in what, from general aspect, I gather to be 

 the nearest region of the milky way, among an immensity of large 

 stars. 



Mr. Henderson observed these stars with great care both in right 

 ascension and declination with the very fine transit, and (in spite of 

 certain grievous defects in the axis) the otherwise really good and 

 finely divided mural circle of the Royal Observatory in that colony. 

 Since his return to England, he has reduced these observations with 

 a view to parallax, and the result is the apparent existence of that 

 element to what, after what has been said, we must now call the 

 great and conspicuous amount of a full second. Mr. Main, to whom 

 I am so largely indebted for allowing me to draw so freely on his 

 labours, has also discussed these results, and comes to the conclu- 

 sion that (as might, perhaps, be expected) the right-ascension ob- 

 servations afford a trace, but an equivocal one, of parallax, but 

 that in declination (I use his words) " The law of parallax is fol- 

 lowed remarkably well. There is scarcely an exception to the 

 proper change of sign, according to the change of sign of the co- 

 efficients of parallax. This is quite as much as can reasonably be 

 expected in a series of individual results obtained from any meri- 

 dional instrument for observing zenith distances. We cannot ex- 

 pect to find the periodical function regularly exhibited by the dif- 

 ferences. On the whole, therefore, we should say that, in addition 

 to the claims of a Centaun- on our attention with relation to its paral- 

 lax, arising from its forming a binary system, its great proper mo- 

 tion, and its brightness, — it derives now much additional import- 

 ance, in this point of view, from the investigation of Mr. Hender- 

 son. This we are at least entitled to assume until some distinct 

 reason, independent of parallax, shall have been assigned for the 

 changes in the declinations. Such I do not consider impossible, 

 having before my eyes the results which Dr. Brinkley derived, in 

 the cases of certain stars, from the Dublin circle. For the present 

 it must be considered that the star well deserves a rigorous ex- 

 amination by all the methods which the author himself has so well 



* I have seen both their images projected on a screen of three thick- 

 nesses of stout paper, the eye being on the opposite side of the screen from 

 that on which the images were depicted. 



Phil, Mag. S. 3. Vol. 19. No. 1 27. Suppl. Jan. 184-2. 2 P 



