III. The Spectrum of Scandium, and its Relation to Solar Spectra. 



By A. FOWLER, A.R.C.S., F.R.A.S., Assistant Professor of Physics, Imperial, College 

 of Science and Technology, South Kensington. 



Communicated by Sir WILLIAM CROOKES, D.Sc., F.R.S. 

 Received June 23, Read June 25, 1908. 



INTRODUCTORY. 



THE present investigation of the spectrum of scandium was undertaken in connection 

 with the work on the spectra of sunspots and .solar prominences with which I have 

 been occupied during the past few years. The presence of scandium in spots and 

 prominences was already well known, but all the desired information \vitli respect to 

 the positions and characteristics of the various lines could not be gathered from 

 published tables. 



THALEN'S observations of the spark spectrum* extend from 4247 to (5305, but 

 though his intensities give a useful term of comparison in some cases, the wave- 

 lengths lack the precision necessary for use with modern solar tables, and a consider- 

 able part of the red is omitted. A few of the Fraunhofer lines were identified with 

 scandium by RowLAXD,t but, probably for want of suitable material for the 

 production of the scandium spectrum, the comparison was far from complete. More 

 extensive observations of the arc and spark spectra have been made by EXNER and 

 HASCHEK,! but, as they extend no further into the visible spectrum than 4744, they 

 scarcely enter the region in which the spectra of spots and prominences are best 

 known. The arc spectrum has been further studied by LOCK.YER and BAXANDALL, 

 but here again the region from 5718 to the red end was not included, and but little 

 attempt was made to classify the lines. 



Attention was specially drawn to the need for the re-determination of some of 

 THALEJST'S wave-lengths in the course of a discussion of some observations of the 

 spectra of sunspots in the region C to D,|| when it was suggested that two very 



* ' WATT'S Index of Spectra,' p. 125. 



t 'Preliminary Table of Solar Spectrum Wave-lengths,' Chicago, 1896. 

 t ' Welleulangen-Tabellen ' (Leipzig und Wien, 1904). 

 'Boy. Soc. Proc.,' vol. 74, p. 538 (1905). 

 || ' Monthly Notices, E.A.S.,' vol. 65, p. 211 (1905). 

 VOL. CCIX. A 443. 5.11.08 



