48 ME. A. FOWLEK ON THE SPECTEUM OF SCANDIUM, 



prominent spot lines recorded at 6210'90 and 6306"02 might be due to scandium. 

 THALEN'S wave-lengths for strong scandium lines near these positions were 6210'0 

 and 6304'0 or 6211/0 and 6305'! when corrected to ROWLAND'S scale and the 

 identifications seemed probable in consequence of the undoubted presence in spots of 

 the scandium line 5 672 '05. The wave-length 6306 '02 was adopted by Father CoRTlE 

 and myself because the spot line could not be distinguished from the telluric oxygen 

 line in that position with the instruments employed, but with greater dispersion 

 MITCHELL* and NEW ALL f subsequently identified the spot line with ROWLAND'S solar 

 line 6305 '88. Observations for checking these identifications were long delayed on 

 account of the difficulty of obtaining a specimen of scandium with which to produce 

 the spectrum, but a few months ago, after an examination of several minerals reputed 

 to contain rare earths, a strong scandium spectrum was obtained from a piece of South 

 African euxenite. The spectrum obtained in this way was admixed with lines and 

 bands of calcium, yttrium, and other substances, but it was quite adequate for the 

 re-determination of wave-lengths, assuming the lines to have been correctly attributed 

 to scandium by THALEN. Measurements of photographs of the arc spectrum of the 

 mineral removed all doubt as to the precise correspondence of the spot lines 6210'90 

 and 6305 '88 with strong lines of scandium first tabulated by THALEN. 



The scandium lines came out so clearly in the spectra of some of the fragments of 

 euxenite that I was induced to carry the inquiry a stage further, in view of the 

 peculiar selection of lines for representation in the solar spectrum and in sunspots. 

 As I have previously remarked : J " The scandium lines which appear in the spots are 

 among the strongest in the arc spectrum, while the possible coincidences with the 

 fainter lines are so few as to be probably accidental. At the same time there are 

 some strong arc lines which are not intensified in the spots ; it is a noticeable fact 

 that these are more intense in the solar spectrum than those which appear in the 

 spots, and the probability is that all of them, like 5527 '03, are related to the enhanced- 

 line class." There is a similar selection of lines in the chromospheric spectrum, as also 

 remarked by LOCKYER and BAXANDALL, but the lines are different from those which 

 appear in spots. 



Similar differences of behaviour have been noted in the case of other elements, but 

 scandium appeared to be rather an extreme example, and further study of the varying 

 intensities of its lines promised to be of value, not only in identifying particular lines 

 with scandium, but in helping to establish the principles to be followed in assigning 

 solar lines of different classes to metallic origins. 



On comparing the euxenite spectrum with the scandium arc recorded by LOCKYER 

 and BAXANDALL it was at once evident that the intensities assigned in the two cases 

 were often widely different. For example, the two lines 5527 and 5672 are given as 



* ' Astrophys. Jour.,' vol. 22, p. 27 (1905). 



t 'Monthly Notices, E.A.S.,' vol. 67, p. 167 (1906). 



J 'Trans. Int. Sol. Union,' vol. 1, p. 228 (1906). 



