6 Proceedings of the Royal Society of Victoria. 



determinations of wavelengths,' while Lockyer's direct com- 

 parison, on 25th April, between the H/3 and D.^ lines of the 

 Nova and those furnished by vacuum tubes, showed the wave- 

 lengths on that date to be normal. The Yerkes plates also, to. 

 a certain extent, support the Lick results ; seven plates taken 

 before 22nd March gave for the wavelength of He 3973, six plates 

 subsequent to that date made it 3970. The cumulative evidence 

 is strongly in favor of the accuracy of the Lick determinations of 

 the absolute wavelengths of the bright lines as against those of 

 Stonyhurst. 



There still remains a difficulty about the dark lines. The 

 Yerkes and Stonyhurst observers agree in representing them 

 as dying out in sM, and completely disappearing before the end 

 of March, owing possibly to decay in brightness of the continuous 

 spectrum. It is, however, noteworthy (1st) that these bands 

 had each of them several components, the more refrangible of 

 which disappeared first, and (2nd) that Lockyer's simultaneous 

 observation and plotting of the intensity curves for the bright 

 bands shows their maxima as shifting from the violet towards 

 the red side of the bands. In other words, the phenomena, taken 

 as a whole, seem to indicate a gradual coalescing of the bright 

 and dark bands, such as the Lick observers found completed in 

 the beginning of April. 



We must not lose sight of the fine dark lines due to metallic 

 absorptions, which were examined with special care by the Lick 

 observers. H, K, D, and D,, were present as very narrow, sharp 

 lines, side by side with the broader absorptions of calcium (and 

 sodium 1). These narrow lines were very slightly displaced 

 towards the red, and agreed — within the limits of experimental 

 error — in showing that their source was recedimg from the sun 

 with a speed of approximately 7 kilometres per second, this 

 value being steadily maintained, up to the middle of August,- 

 quite independent of the changes in either the heavy absorptions 

 or the bright lines. 



1 A fact of which he himself appears to be fully conscious. It may be added that he 

 considers a good many of his plates to have been over-exposed to such an extent as to 

 unduly broaden the lines. Can this have produced sligrht displacements of the maxima, 

 which we know were never central 1 



2 When the last recorded measurements were made. 



