442 



Mr. J. Norman Lockyer. 



List of Additional Elements examined for Enhanced Lines. 



Aluminium. 



Lead. 



Sulphur. 



Antimony. 



Lithium. 



Tantalum. 



Barium. 



Manganese. 



Tellurium. 



Beryllium. 



Molybdenum. 



Thorium. 



Bismuth. 



Nickel. 



Titanium. 



Carbon. 



Niobium. 



Tin. 



Cadmium. 



Palladium 



Tungsten. 



Cerium. 



Potassium. 



Uranium. 



Chromium. 



Rhodium. 



Vanadium. 



Cobalt. 



Silicium . 



Yttrium (and 



Copper. 



Silver. 



Erbium). 



Erbium (and 



Sodium. 



Zinc. 



Yttrium) . 



Strontium. 



Zirconium. 



Lanthanum. 







The list of lines is not given here for the reason that so far the 

 series of comparisons with a Rowland grating of 21 ft. radius is not 

 complete. Nevertheless the approximate wave-lengths already 

 determined are of the same order of accuracy as those of the chromo- 

 spheric and stellar lines, and the supposed coincidences depend upon 

 the occurrence of several lines of a given substance rather than 

 upon an absolute agreement in the deduced positions of any single 

 line. 



In the former paper I drew attention to the fact that while the 

 enhanced lines of magnesium (4481'3) and calcium (H and K) 

 remained feebly visible in the hottest stars included in the discus- 

 sion, the enhanced lines of iron vanished entirely in such stars, and 

 were thinner than those of magnesium and calcium in stars which 

 are approaching the highest temperature as determined by the length 

 of the spectrum in the ultra-violet. Similar differences of behaviour 

 have also been noted among the substances which have since been 

 investigated. 



These differences in the case of metals of the iron and calcium 

 groups are shown in the following table, in which the stars are 

 arranged in the order of temperature previously deduced from the 

 discussion of the lines of iron, magnesium, and calcium, and the 

 name of each substance considered is placed opposite that of the 

 hottest star in which its enhanced lines remain visible. 



It thus appears that while calcium remains visible up to the highest 

 temperatures, the enhanced lines of strontium probably cease to be 

 visible at temperatures higher than that of 7 Cygni, while those of 

 barium have not yet been certainly traced in any of the stars. The 

 order of appearance of the metals of the calcium group thus con- 

 forms with the cb 3mical order. Of the metals of the iron group, 



