A. MATHEMATICS AND ASTRONOMY. 17 



*' the western end of this nebula has moved relatively to its 

 contained stars from 1833 to 1862, and again from 1862 to 

 1875, and always in the same direction." 



The author also directs attention to the Trifid Nebula (G. 

 C. 4355), which was suspected by Sir John Herschel to have 

 a proper motion. Professor Holden confirms Herschel's sus- 

 picion. This is the first large proper motion detected in 

 any nebula, and is of great interest in the theoretical ques- 

 tions relating to the distance and nature of these bodies. 

 Both of these nebuljB will receive further attention. 4 Z>, 

 3Iay, 1876, 341. 



COLORS OF DOUBLE STAES. 



In the Astronomical Register for May, 1876, Mr. Sadler 

 gives a list of sixty-three double stars, with the colors that 

 he has noted for the components. His observations w^ere 

 made with a 6^-inch silvered-glass reflector (silvered-glass 

 reflectors possess considerable advantages in such investi- 

 gations, as the natural color of an object is less affected 

 than when a refractor is used), and appear to have been 

 made with great care. An interesting comparison with the 

 work of former observers is given at the close of his paper. 

 Smyth, Sestini, Herschel, South, Webb, Struve, and others are 

 full of notes on this subject, which deserves attention, and 

 is well suited to amateur observers. 



THE EUGBY (temple OBSEEVATOEy) AND ME. GLEDIIILL's 

 CATALOGUES OF DOUBLE STAES. 



In the 3Iemoirs of the Royal Astronomical Society (vol. 

 xlii.) Messrs. Wilson and Seabroke, of Rugby School, have 

 given to astronomers the results of their micrometric meas- 

 ures of double stars during the years 1871-74. The measures 

 were made with the 8^-inch equatorial by Alvan Clark which 

 was formerly used by Dawes. Rugby has selected those 

 even-numbered stars of Struve's Catalogue which are south 

 of 50 of N. declination for subjects of observation, and re- 

 cords 1152 measures of these. The observations show 2:reat 

 fidelity and skill on the part of the observers, and are a val- 

 uable contribution to this branch of astronomy. 



Many interesting binaries were observed, some of consid- 

 erable difficulty; and this catalogue will be an essential help 



