174 Scientific Intelligence. 



methods, and under more favorable conditions for observation, 

 has enabled the authors to determine more accurately the position 

 and character of the principal line. The position determined, 

 corrected for the earth's motion and assuming that the nebula has 

 no motion of its own, is A. 5004*75. A comparison with the bright 

 line of a hydrogen vacuum tube confirmed the conclusion reached 

 in 1874 that the nebula has very little of any sensible motion in 

 the line of sight. It is also shown that the principal line is not 

 coincident with but falls within the termination of the magnesium- 

 flame band. As regards the character of the principal line it is 

 found that it is sharply defined and presents nothing of the pecu- 

 liarity of a fluting. Confirmatory observations by other astrono- 

 mers are quoted, and a postscript dated June 15, states that a 

 telegram received from the Lick Observatory announces that Mr. 

 Keeler had confirmed, in 2 5, the position assigned to the princi- 

 pal line, namely, as not coincident with but falling within the 

 terminal line of the magnesic oxide band. It is hence certain 

 that the chief line is not due to magnesium or its oxide. 



A second paper gives some important results of an examination 

 of new photographs of the spectrum taken March 14-17. These 

 photographs, of almost the same part of the nebula as the photo- 

 graph of 1889, showed the lines of hydrogen at h and at H strongly 

 impressed upon the plate, though these lines were carefully searched 

 for in vain in the former photographs ; also the first two lines of 

 the ultra-violet series in the white stars described in 1879. Four 

 of these lines had been photographed in the spectrum of hydrogen 

 by Dr. H. W. Vogel, in 1879, and the entire series, with the ex- 

 ception of one, has been since obtained by Cornu in exceptionally 

 pure hydrogen. The line a at A 3887*8 is strong, and the next 

 line /5 at A 3834*5, though much fainter, is certainly present. 

 Between the hydrogen lines a and ji there is a line stronger 

 even than a, Avhich has a wave-length of about A 3868. No line 

 is found in the photograph exactly at the place of the solar line 

 K ; the position of this line appears to correspond to a gap be- 

 tween two lines on the plate. 



The strong line which was first seen in a photograph of the 

 nebula taken in 1882 is certainly stronger than H;/, aud is by far 

 the most powerful line in the photographic region, and in position 

 it is found to be slightly less refrangible than A 3724. It is be- 

 lieved the line will be found to fall between A 3725 and A 3726. 

 It is certain that the line does not coincide with any one of the 

 three components of the magnesic oxide triplet, but is less refran- 

 gible than the middle line at A 3724, and falls between this line 

 and the first line of the triplet at A 3730. 



A marked feature of the lines is their abruptly different inten- 

 sities at different parts of their length, giving the blotchy appear- 

 ance which is characteristic of the lines in the visible spectrum. 

 These brighter blotches are sharply bounded, showing that the 

 different parts of the nebula are distinct and become suddenly 

 brighter than the neighboring parts. The lines of the new pho- 



