ASTRONOMY. 189 



Centauri must be deferred till the next year, as the paper is not now 

 before the writer. 



A new determination of the parallax of 61 Cygni, by Dr. Ball, forms 

 the subject of the next paper. This determination differs from others 

 on the same object in one particular, viz, that the preceding star instead 

 of the followini^ one has been observed. The method of observation 

 used is that of differences of declination, and the observations were 

 made on thirty-five different nights between July 3, 1877, and June 1, 

 1878. The resulting parallax is 0".4G5, in pretty good accordance with 

 the results of Bessel (last three months 0".54), Struve (0".51), and 

 AUWERS (0".o(»). 



A third paper, also by Dr. Ball, describes the first results of a series 

 of reconnoitering observations in search of stars with a large annual par- 

 allax. These observations are only intended to reveal large parallaxes 

 (0".7) or more, and each object is only observed twice a year with six 

 months' interval, when it is 90^ from the sun, and at the two extremities 

 of the major axis of the parallactic ellipse. ^The paper contains the dis- 

 cussion of the observations of forty-two objects, chiefly red aiid variable 

 stars. The result is that in almost every case the parallax is certainly 

 less than 1", and most probably does not exceed 0".5. These objects will 

 therefore not be observed any further, but it is Dr. Ball's intention to 

 continue this kind of observations. His working list contains red and 

 variable stars, stars with a large proper motion, and others chosen for 

 various reasons, nearly all north of the 30° parallel. 



According to Herr Geelmuyden, of Ghristiania, the star Arg. Oeltzen, 

 11677, has a perceptible parallax (A. N. 2237). This star of the ninth 

 magnitude has a proper motion of — 0^507 and + 0".21. The resulting 

 parallax, 0".27 from measures of A a and 0".24 from metisures of A'? with 

 a star preceding, is only considered provisional, but the subject seems 

 worth following up. 



DOUBLE STARS. 



In 1841 and 1842 the Pulkova refractor was used for an examination of 

 the northern hemisphere in search of double stars. The second part of 

 the catalogue thus formed embraces systems, the components of which 

 are of or above the eighth mag., and the distance between which are 

 from 32" to 2'. Most of these objects have never been observed micro- 

 metrically, and the series of heliometer measures of some of them, which 

 Dr. SCHTJR, of Strassburg, publishes in the A. N. 2255-56, will there- 

 fore be of interest, though only comprising a small number of objects. 

 Systems closer than 40" were measured by quadruple distances, wider 

 pairs by double distances. By means of an artificial pair of stars it was 

 found that the position angle had no appreciable influence on the meas- 

 ures of distance, and that the two methods of measuring the distances 

 showed no constant diftereuce. 



Volume XLIV of the Memoirs of E. A. S. contains a very extensive 

 work by Mr. BURNHAM: "Double-star observations made in 1877-'78, 



