284 Prof. J. Norman Lockyer. [June 21, 



the spectrum of y3 Lyrae greatly resembles that of Bellatrix, the com- 

 ponent B in this case lying between us and component B. As the 

 eclipse is not total, however, the lines special to B appear with 

 reduced intensities ; the lines joining the spectrum of ft Lyrse to that 

 of Bellatrix indicate the principal lines of 'component B. At the 

 secondary minimum, on the other hand, component B lies in front of 

 component B, and the spectrum consequently bears a greater resem- 

 blance to that of Bigel. This is shown by the lines joining those of 

 /3 LyrsD to the spectrum of Bigel in Plate 2. 



The difference is especially noticeable in the case of the lines near 

 \4471, 4481, 4388, and in the group of four lines a little less refran- 

 gible than HS. It will be seen that near principal minimum 4471 is 

 stronger than 4481, as in Bellatrix, while about secondary minimum 

 4481 is stronger than 4471. 



If the eclipses were total, the variations of the spectrum might be 

 expected to be still more striking. 



7. In addition to dark lines there are several bright ones, which change 

 their positions with respect to the dark ones. 



The photographs show conspicuous bright lines about wave-lengths 

 4862(H /3 ), 4715, 4471, 4388, 4340(H V ), 4101 (H), 4025, and 

 388 7 (H^). Other fainter ones also appear in some of the best photo- 

 graphs. The line at 4471 (Lorenzoni's /) is the well-known line 

 which appears in the spectrum of the solar chromosphere, and those 

 at 4025 and 4715 are amongst the brightest lines photographed with 

 the prismatic camera during the total eclipse of the sun on April 16, 

 1893. 



The displacements of the bright lines described by Pickering are 

 confirmed in the main by the Kensington photographs. In the first 

 seven photographs in Plate 1 taken between principal and secondary 

 minimum, the bright lines lie on the less refrangible sides of the dark 

 ones, at secondary minimum the broad bright lines are almost 

 bisected by dark ones ; while from secondary minimum to prin- 

 cipal minimum the bright lines are more refrangible than the dark 

 ones. The investigation of the movements of the bright lines must, 

 however, be now carried on in the light of the knowledge gained 

 with regard to the existence of two sets of dark lines. 



If we consider the displacements of the bright lines with reference 

 to the dark lines of component B, we find that they are always in the 

 same direction as those of component B with respect to B. Thus in 

 the first half of the period, the bright lines, as well as the dark lines 

 of component B, are less refrangible than those of component B, while 

 during the second half they are more refrangible. The bright lines, 

 however, do not keep a constant position with respect to those of 

 component B, although displaced in the same direction. 



8. The bright lines are brightest soon after secondary minimum. 



