488 



Dr. and Mrs. Huggins. 



[May 19, 



is about X 5014. and the line may well be one about this position 

 which is frequently seen bright at the Sun's limb. 



It may be added that though three faint bright lines are to be seen 

 in the star's spectrum, not far from the place of the second nebular 

 line, no one of them can be regarded as that line. Indeed no certain 

 evidence exists that the chief nebular line occurs without the second 

 line. In some cases of my early observations on the nebulae in 

 which I recorded the spectrum as consisting of one line only, I have 

 since with better instruments been able to see the second and the 

 third lines as well. The origin of the second, as well as that of the 

 chief nebular line, is not known. Professor Keeler has shown that the 

 second nebular line is not coincident with the double line of iron, 

 which is very near it. 



The conclusion that the spectrum of the Nova has no relationship 

 with that of the bright-line nebulas would be strengthened, if further 

 confirmation were needed, by the absence in a photograph we took of 

 the spectrum of the New Star of a very strong ultra-violet line which 

 is usually found in the spectrum of the nebula of Orion. 



Comparison with the Hydrocarbon Flame and Carbon Oxide. — The 

 brightest line in spectrum of the Nova, with the exception of F, 

 falls near the brightest edge of the green fluting of the hydro- 

 carbon flame. Direct comparisons showed the star line to fall a little 

 to the red side of the edge of the fluting ; but, allowing for a shift of 

 the star's spectrum, the place of the line would be near, though not 

 coincident with, the brightest edge of the fluting. 



The character of the star line leaves, however, no doubt on this point, 

 for it is multiple with the brightest and most defined line on the blue 

 side, contrary to the fluting which is defined on the red side, and gradu- 

 ally falls off towards the blue. If any uncertainty could be supposed 

 still to remain, it was wholly removed when we found no brightenings 

 in the star's spectrum corresponding to the other flutings of the hydro- 

 carbon flame. A bright band in the blue falls just beyond the fluting 

 in this region. This band may have the same origin as a similar 

 band in certain of the Wolf-Rayet stars. 



We conclude that the spectrum of the Nova has no relationship with 

 the usual spectrum of comets. 



We found from direct comparison that the different set of flutings 

 characteristic of the carbon oxide spectrum was not represented by 

 any corresponding brightenings in the spectrum of the Nova. 



Comparison with Magnesium. — It was not unreasonable to suppose 

 that the star line might have its origin in magnesium, the triple line 

 of which at b falls almost at the same place. The comparison showed 

 the stellar line to fall upon the more refrangible pair of the mag- 

 nesium triplet, and to overlap it slightly on both sides, but rather 

 more on the blue side. Considering that with the resolving power 



