622 Mr. William Huggins [May 13, 



to assume a system of at least six bodies, all moving with different 

 velocities. 



In Fig. 1, Plate I., is reproduced a photograph of the blue part 

 of the spectrum taken at Harvard Observatory with a prism placed 

 over the object-glass. The dark absorption lines on the blue side of 

 the bright lines are well shown. 



It is of great importance to state that the waning of the star 

 was not accomjDanied by any material change of its spectrum, but only 

 of such aj)parent changes as might well come in when parts of an 

 object differ greatly in brightness. On March 24th, when the star's 

 light had fallen so low as to nearly the eleventh magnitude, we could 

 still glimpse the faint continuous spectrum, upon which the remark- 

 able quartet of bright lines still shone out without any great change 

 of relative intensity. Prof. Pickering informs me that on his 

 plates the principal lines in the photographic part of the spectrum 

 " faded in the order K, H, a, F, h, G, the latter becoming brighter as 

 the star was faint." Omitting the calcium lines H and K, which 

 varied, the order of disappearance agrees with that of the sensitive- 

 ness of the plate for these parts of the spectrum, and is in accordance 

 with the view that the star's spectrum remained without material 

 alteration through this great range of magnitude. 



How are we to account for the appearance and doings of this new 

 star, or rather stars ? For, as we have seen, the great shifts in the 

 spectrum of the bright and dark lines, the bright to the red, and the 

 dark to the blue, appear to show two bodies having relative motion 

 in the line of sight of about 550 miles a second. Now, during the 

 whole time, some seven weeks, that the star was under observation, 

 this relative velocity was maintained without any great alteration, 

 though it is probable that small changes, beyond the reach of our 

 instruments, took place. 



A reasonable explanation of these phenomena may perhaps be 

 found if we venture to assume, though with considerable hesitation, 

 as the subject is obscure, two gaseous bodies, or bodies with gaseous 

 atmospheres, moving away from each other after a near approach, in 

 parabolic or hyperbolic orbits, with our sun nearly in the axis of the 

 orbits ; the comi^onents of the motions of the two bodies in the line of 

 sight, after they had swung round, might well be as rapid as those 

 observed in the new star, and might continue for as long a time 

 without any great change of relative velocity. Unfortunately, infor- 

 mation as to the motions of the bodies at the critical time is wanting, 

 for the event through which the star became suddenly bright had 

 been over for some forty days before any observations were made with 

 the spectroscope. 



Analogy from the variable stars of long period would suggest 

 the view that the near approach of the two bodies may have been 

 of the nature of a periodical disturbance, arising at long intervals 

 in a complex system of bodies. Chandler has recently shown in 

 the case of Algol that the minor irregularities in the variation of 



