Enhanced Lines of Titanium, etc., in Fraunhoferic Spectrum. 255 



" Enhanced Lines of Titanium, Iron, and Chromium in the 

 Fraunhoferic Spectrum." By Sir J. NORMAN LOCKYER, K.C.B., 

 LL.D., F.E.S., and F. E. BAXANDALL, A.E.C.S. Received 

 July 13, 1904. 



In previous publications it has been shown that the enhanced lines 

 of some of the metals are prominent in the spectra of a Cygni* and 

 the sun's chromosphere!, while it is generally recognised that the lines 

 in the Fraunhoferic spectrum are mainly the equivalents of lines in the 

 arc spectra of metals. In connection with the work on enhanced lines 

 it has been noted that some of them, at least, appear to correspond 

 with comparatively weak solar lines to which Rowland has attached no 

 origin. With the object of possibly tracing some of the unorigined 

 solar lines to their source, a careful comparison has been made between 

 the enhanced lines shown in the photographic spark spectra of titanium, 

 iron, and chromium, and the solar lines. The photographs used for 

 this purpose were all taken with a Rowland grating, under exactly 

 similar conditions, and on such a scale that the length of spectrum 

 between K and F is about 14 inches (35 cms.). The chemical elements 

 named were first selected for investigation because they furnish by far 

 the greater number of enhanced lines which have been shown to occur 

 in the spectrum of a Cygni. It was an easy matter, owing to the 

 many solar coincidences with lines of these elements, to adjust the 

 compared photographs and get the spectrum lines in proper alignment. 



It was found that many of the enhanced lines fell exactly and 

 squarely on isolated lines of the solar spectrum, and in these cases the 

 solar wave-lengths were adopted, and the identification considered 

 established. If, however, for any of these solar lines Rowland had 

 given alternative origins, special comparisons were made of the 

 enhanced line photograph and those of the metals given by Rowland. 

 Notes were made as to the agreement or non-agreement of the 

 metallic lines involved, and also of the relative intensities in their 

 individual spectra, so that due weights could be given to the respective 

 metallic lines which were thought to conjointly produce compound 

 solar lines. 



Where there was any doubt as to the exact coincidence of a metallic 

 and solar line, or where by the close grouping of several solar lines it 

 was not possible to say by direct comparison to which solar line the 

 metallic line corresponded, careful measures were made of the metallic 

 line, and its wave-length found by interpolation between closely 

 adjacent lines of known wave-length. The resulting wave-lengths 



* ' Koy. Soc. Proc.,' vol. 64, p. 321. 

 f 'Boy. Soc. Proc./ vol. 68, p. 178. 



