Astronomy. • 79, 



the use of the filar micrometer for such large distances as those 

 under consideration is likely to be accompanied with considerable 

 casual error, and, unless great care is taken, with large systematic 

 error. The conclusions of Messrs. Wolf and Pritchard as to the 

 relative motions in the group have thus been unfortunately 

 vitiated, and must be replaced by those formulated at the end of 

 the preceding section." 



Another result of the discussion is that the probable errors of 

 the heliometer measurements rapidly increase with the magnitude 

 of the stars observed, so that Dr. Elkin expresses the purpose 

 hereafter to restrict his investigations to stars which do not fall 

 much below 8'1 or 8'2 magnitude, much as this will limit its field 

 of activity. 



2. Annals of the Astronomical Observatory of Harvard Col- 

 lege, E. C. Pickering, Director, vol. xvii. The Almucantar; an 

 investigation made at the Observatory in 1884 and 1885 ; by S. 

 C. Chandler, Jr., Cambridge, 1887. — This volume of the Har- 

 vard Annals is devoted to the description and the theory of the 

 new instrument invented by Mr. Chandler, and the results of 

 observations and experiments with it. The almucantar consists 

 of a telescope mounted upon a base that floats in mercury. The 

 field is crossed by a reticule of horizontal lines, and one vertical 

 line to mark the center of the field. The observation consists in 

 noting the time of transit of a star across an almucantaral circle, 

 such a circle taking the place of the meridian plane in meridian 

 instruments. 



Mr. Chandler considers it a fair conclusion from his experi- 

 ments that the probable accidental deviation of the float from the 

 mean position of equilibrium, is in the neighborhood of one- 

 twentieth of a second of arc. 



This mode of axial rotation of the sight line of the telescope he 

 believes, therefore, to be nearer perfection than can be certainly 

 attained by any instrument swinging on pivots in a vertical 

 plane. If further investigations, especially with new forms of 

 the instrument some of which are suggested by Mr. Chandler, 

 shall confirm these conclusions, the almucantar seems certainly 

 destined to be used for the solution of some of the most difficult 

 astronomical problems. 



3. Parallax of a Tauri. — Professor Hall has published in 

 Gould's Journal the results of his measurements of a Tauri and 

 its companion made in October and March last. Director von 

 Struve had obtained the very large parallax of 0"*516. Professor 

 Hall obtains, however, the small value of 0"*102. One series of 

 Dr. Elkin's measurements of this star, made with the Yale Heli- 

 ometer, indicates a small rather than a large parallax. 



4. Publications of the Morrison Observatory, Glasgow, Mo., 

 ISTo. 1, 4°, pp. 111. — The Morrison Observatory was established 

 by a donation from Miss Berenice Morrison, and the present publi- 

 cation is prepai-ed by the Director, Mr. Carr W. Pritchett. It 

 contains a description of the observatory and its instruments, the 



