ASTRONOMY. 



59 



fouud from his two series the values 0"-65 and ()"-55 instead of 0"-75). 

 It seems best, then, to represent the influence of the systematic error 

 by a trigonometric series depending upon the angle formed by the di- 

 rection of the measures with the vertical, or more simply to admit for 

 each position of the eye a constant error, varying slightly with the hour 

 angle. Mr. Elkin proceeds thus, and his idea seems very rational. It 

 is possible that Mr. Gill's second series of observations might be repre- 

 sented in the same way without introducing anj^ hypothesis concerning 

 the orbital motion of a Centauri. 



After having given an idea of the delicate questions which Mr. Gill 

 and Mr. Elkin have had to solve, it remains to present the results ob- 

 tained : 



It is known that the observatory at the Cape will possess in two years 

 from now a 7-inch heliometer, while Mr. Elkin has at his disposal, 

 at Yale College, the most beautiful heliometer known to-day (6 inches 

 aperture). It is quite possible that within ten years stellar astronomy 

 may be enriched by discoveries of the greatest value. (O. Callandreau, 

 in Bull. Astroii., January, 1885.) 



Parallax of Mi o^ Eridani. — Professor Hall publishes in No. 2682 of 

 the Astronotnische Nachrichten the results of observations made in 1883 

 and 1884 to determine the annual parallax of the star 40 o^ Eridani. 

 The principal star of this system has a proper motion of 4" a year ; and, 

 at a distance of 82", there is a double companion, which has the same 

 proper motion, while nearly between them is a small star which does 

 not move. Professor Hall finds for the parallax of 40 Eridani, tt = 

 0"'223+0"-0208, a result rather smaller than might have been ex- 

 pected, but one which he considers worthy of considerable confidence. 



Parallax of 2 2398 (P. M. 2104).— Dr. Lamp, of Kiel, has inves- 

 tigated* the annual parallax of this double star, the components of 

 which are 8-2 and 8-7 magnitude, according to W. Struve, and for the 

 epoch 1832-17, distance 12"'420, and position-angle 1340-37. Later meas- 

 ures by Madler,Dembowski, and Engelmann show a change of relative 



'Astron. Nadir., 2676. 



