140 Engelmann on Double' Stars. 



described, may be following the example of a third £, that of 

 Hercules, a wonderful pair, of very short, though not well 

 ascertained period (Struve giving it but 14 years, Sm. 35) ; 

 which having been measured by the latter at 1"*2 (1842 "5 7), 

 has of late years actually closed up to apparent unity. £ Bootis 

 is rendered additionally remarkable by Engelmann' s confirma- 

 tion of Struve' s idea, that both stars are variable. 



24. a Herculis. The stationary character of this fine object 

 is confirmed. 



25. & Herculis. This also seems, notwithstanding previous 

 conjectures, to be only optically connected. 



26. 8 Serpentis. 3"*313. ' 190°'73 (1864-42).— Demb., 

 3"-198. 192°-20 (1863-43). — Secchi, 3"-066. 195°*52 

 (1855*89). The suspected motion in this pair is now suffi- 

 ciently evident. 



27. k Herculis. Stationary. 



35. f Ooronce. 6"-195. 302°'8 (1864-48).— Secchi, 

 6"-213. 301°-71 (1856-49).— Struve, 6 /, .002. 300°-86 

 (1829'7). Hence Engelmann infers a slight, but pretty certain 

 change of angle. 



37. <r Coronw. 3"-115. 190°-52 (1864-45).— Demb., 

 2"*759. 190°*06 (1863-09). The continued motion of this 

 beautiful binary is evident, and it is to be hoped that we shall 

 soon be in possession of data for computing a more satisfactory 

 orbit. 



38. v Coronce. l"-09. 28°-25 (1864-45).— Demb., 0"-81. 

 19°-04 (1863-03).— Secchi, // -535. 4°-5 (1859-48). The 

 rapid movement of this most interesting pah* is apparent, even 

 from year to year, and its mutual divergence has brought it 

 within the reach of even moderate instruments. Minute as 

 the object is, how much it reveals to us of the wonderful 

 mechanism of the universe ! It is now an excellent compa- 

 rative test in conjunction with the more difficult £ Bootis. 

 Eecently (1865*46) I have found that 111 of my achromatic will 

 strongly elongate it, and 450 show a division equal to 0'4, if 

 not 0*5, of the disc of B. In such comparisons as these, 

 however, it must be borne in mind that the quality of the 

 eyepiece is somewhat involved, as well as that of the object- 

 glass. 



42. 70 OpMuchL 5"*425. 104°-77 (not good), (1864-48). 

 Demb., _5"*666. 104°*96 (1863*06). The distance continues 

 to diminish, the angle to increase. 



43. X Ophluchi. l"-777. 23°-4 (not good), (1864-45). 

 — Demb., r-442. 19°*61 (1862*93). Motion very obvious. 



47. e-4 and e 2 5 Lyrcc.—e\ 3"*295. 19°-8 (1864*45).— 

 Demb., 3"*045. 19 D *35 (1863*09).— Secchi, 3"*07. 22°*42 

 (1856*24).— Struve, 3"*034. 26°*06 (1831*44). Angular 



