138 Engelmann on Double Stars. 



worthy of preservation, and that not less than 1500 were made 

 in 1862 and 1863, they will form some idea of the extraordi- 

 nary amount of perseverance which has been brought to bear 

 by Dr. Draper upon this interesting object, as well as of the 

 uncommon fertility of invention and resource which are ap- 

 parent throughout his very striking and valuable memoir. 



ENGELMANN ON DOUBLE STAES. 



During the course of last year Dr. R. Engelmann, the ob- 

 server at Leipzig, completed his measurements of 48 double stars 

 with the 12 feet equatoreal of 8 inches aperture (Paris measure), 

 which Steinheil, of Munich, has recently erected in that obser- 

 vatory. It may be interesting to our astronomical readers to 

 be made acquainted with his results, and those of other 

 observers cited by him, so far as they relate to the objects 

 already described in our Double Star List, of which we shall 

 adopt the order and numbering. 



1. £ Ursce Majoris. The components of this fine pair are 

 still relatively stationary. 



4. aGeminorum. 5"-526. 242°-86 (1864-16).— Dembowski 

 gives 5"-381. 241°-66 (1863-03).— Secchi, 5"-368. 245°-13 

 (1855-82). — The change of angle is very apparent, and in a 

 few years we may hope for a more satisfactory determination of 

 its period. 



5. £ Oancri. Engelmann could not 'divide A and B (the 

 close pair), and speaks doubtfully even of the direction of the 



A 4- "R 



elongation. For and (that is, for the distance and 



2 



angle between and the centre of the compound mass of 

 A and B), he gives 5"-49. 141°-3 (1864-31).— Demb., 5"'477. 

 140°-56 (1863-05).— Secchi, 4"-929. 141°-2 (1855-19). The 

 angle is evidently changing more than the distance. It seems 

 rather singular that the large aperture of the Leipzig achro- 

 matic (8^- English inches) should have failed to deal with the 

 close pair : but from some optical imperfection it evidently 

 gives too large star-discs, 0"'7 to 1" for 3 or 4 mag\, so that it 

 will only elongate <y 2 Andromeda?, which Dembowski could 

 frequently separate with an inch less of aperture. In this 

 instance Steinheil^s work must be pronounced inferior to that 

 of Merz. My Clark, too, has obviously a great advantage in 

 proportion to its size, as, with only 5-^ inches, 450 almost 

 divided £ Cancri, when it must havebeen still closer, 1865-17. 

 But the superior action of a really parabolic speculum on this 

 class of objects was fully proved a little a'fterwards (1865*27), 

 when with 8 inches of silvered glass, wrought by Mr. With to 

 a focus of only 6 feet, I saw with a power of about 300 an 



