42 Dr. and Mrs. Muggins. On Wolf and [Dec. 11, 



Professor Vogel observed two other stars with similar spectra, of 

 which the main feature is the very bright band in the blue region, 

 namely, Arg. Oeltzen 17681 and Lai. 13412. These stars are too low 

 in southern declination to be reached from our observatory. 



Vogel places the bine band in Lai. 13412 at X 469, which shows 

 that it has a position similar to that of No. 4001 and of Dr. Copeland's 

 star. In the case of Arg. Oeltzen 17681, Vogel makes the band to 

 extend through about the entire range of refrangibility occupied by 

 the two positions of the blue band in the Wolf-Ray et stars according 

 to his measures of them, namely, from X 461 to X 470, with a maximum 

 at the place where they would overlap, namely, X 466. 



Let us consider the four stars with an intensely brilliant blue band 

 which we have examined ; in two of them the band extends from 

 about X 464 to X 467, and in the other pair the band has a less 

 refrangible position, from about X 4G6 to X 471, but there is also in 

 the case of each pair a very faint band visible, or suspected, at the 

 position of the blue band in the other pair. Further, in Arg. Oeltzen 

 17681, Vogel found the bright band sufficiently long to include both 

 positions of the band. 



One suggestion which presents itself is whether these bands, or, 

 more correctly, these groups of bright Hues, may be variable, so that, 

 under certain conditions, one or other of them becomes brilliant. 

 Such a state of things would reconcile our observations of +37 3821 

 with the earlier measures of Dr. Copeland, and, indeed, might pos- 

 sibly explain, if this variability should be established, the circum- 

 stance that so accurate an observer as Professor Vogel did not detect, 

 -even with his smaller instrument in 1873, the very large difference of 

 position of the band in 4001 from that of the corresponding band in 

 the stars 4013 and 3956, which was so conspicuous in 1883, and is so 

 still at the present time. In the broad characters of their spectra, 

 and in their magnitudes, the Wolf-Rayet stars have remained un- 

 changed since the discovery of their remarkable spectra in 1867. 



As the only direct evidence of such a variability rests upon the 

 change of position of the band in Dr. Copeland's star since his 

 observation of it in 1884, I wrote to Dr. Copeland to ask if his 

 position rested upon sufficiently accurate measures or was arrived at 

 by estimation only. In reply he says : " The place of the blue line 

 (rather band) in D.M. +37 3821, given in the 'Monthly Notices,' is 

 a mere estimate to show the character of the star." 



Whether any change of position of the band has taken place must 

 therefore remain at present uncertain ; but, independently of any such 

 direct evidence of variability, the two positions of the very bright 

 blue band, with the suspicion of faint bands at the alternate positions, 

 appear to us suggestive of possible variation, especially when we 



