432 Prof. J. Norman Lockyer. [Feb. 11, 



then appeared to be slightly brighter than on February 3, when the 

 star was first observed at Kensington. With the 10-inch refractor 

 and Maclean spectroscope, C was seen to be very brilliant, and there 

 were four very conspicuous lines in the green. Several fainter lines 

 were also seen, and a dark line was suspected in the orange. I 

 noticed that some of the lines, especially the bright one near F, on 

 the less refrangible side, appeared to change rapidly in relative 

 brightness, and this was confirmed by Mr. Fowler. 



Observations of the spectrum were made by Mr. Fowler with the 

 3-foot reflector and the Hilger 3-prism spectroscope. Of the four 

 most conspicuous lines in the green, F is the most refrangible, and 

 comparisons with burning magnesium showed one of them to be 

 sensibly coincident with the edge of the magnesium fluting at 500'6. 

 The least refrangible of the four bright green lines was found to be 

 slightly less refrangible than the carbon fluting near X f517 ; it gives 

 no indications of a fluted character, and further observations seemed 

 to suggest that it was magnesium b, unless there be a very great 

 change of position due to motion in the line of sight. The fourth 

 line, which lies between F and 500*6, is about one-third of the dis- 

 tance between them from F, and its wave-length, assuming the star 

 to be at rest, was estimated to be about 490. 



In addition to these, the G line of hydrogen was distinctly visible, 

 and also a group of lines between G and F. The latter were not 

 measure ^, as they appear on the photographs. 



Amongst the fainter lines, one was estimated to be near X 527, and 

 is probably the iron line at E. By comparison with the spectrum of 

 manganese chloride burning in a spirit-lamp flame, another line was 

 found to be sensibly coincident with the edge of the brightest fluting, 

 X 557-6. 



There was a bright line a little more refrangible than C, and the 

 D line was faintly visible. 



Photographs. 



The first photograph was exposed from 10.20 to 11.50 P.M , and the 

 second from 12 to 2 A.M., Feb. 7, the 6-inch object-glass and prism being 

 employed in each case. The same number of lines is shown in both 

 photographs, the sky not being so clear during the second as during 

 the first exposure. Twenty bright lines have been measured, and 

 their wave-lengths are given in the accompanying table. 



The table also shows probable coincidences with the lines in the 

 spectra of the Wolf-Rayet stars, as photographed by Professor 

 Pickering ; dark lines in the Orion stars, photographed at Kensing- 

 ton ; and bright lines in the Orion nebula, photographed at Westgate. 

 This part of the subject will be discussed in a subsequent paper. 



