On the Enhanced Lines in the Spectrum of the Chromosphere. 183 



In the above list of solar-titanium lines there are thirty-three which 

 are not " enhanced " in the spark spectrum. It will be seen that 

 twenty-three of these — or 70 per cent. — have no corresponding line 

 (within 0*3 tenth-metre) in Professor Frost's record of eclipse lines. 

 Of the nine eclipse lines in the table which do agree approximately in 

 position with unenhanced titanium lines, two are with certainty due to 

 other metals, and in another case there is more evidence for an iron 

 origin than one of titanium. These are indicated in the column for 

 remarks. The remainder are nearly all lines of insignificant intensity. 



Of the twenty " enhanced " lines of titanium which occur in the list, 

 nineteen have corresponding lines in Professor Frost's eclipse spectra,, 

 the remaining one being also possibly represented, but it falls so near 

 the strong Hy line that it might be easily masked. Not only are they 

 represented in the eclipse spectra, but in nearly every case the corre- 

 sponding eclipse line is a prominent one, as will be gathered at once 

 from a glance at the tabular list given. 



Professor Frost summarily dismisses the significance of the enhanced 

 lines of titanium in the eclipse spectra, because " most of them occur as 

 quite strong lines in the ordinary dark line spectrum, and hence would 

 be expected to appear in the reversing layer, as they do." But if he 

 would expect one line of a certain solar intensity, he should expect all 

 lines due to the same element which are of an equal solar intensity, to 

 appear in the eclipse spectra. Yet another glance at the foregoing 

 table will show that many of the titanium lines strongly represented 

 in the eclipse spectra are of the lowest intensity in the Fraunhofer 

 spectrum, and that if lines of a certain solar intensity be considered, 

 those that are enhanced lines appear in the eclipse spectra, whereas 

 the unenhanced ones do not. 



In this comparison no account has been taken of the relative 

 intensities of the lines in the titanium spectrum itself. Hasselberg 

 has published* a lengthy list of titanium arc lines, and in the region 

 covered by the eclipse spectra records about 250. To compare all 

 these with the eclipse lines would take too much time and space, 

 nor is it necessary. To show the difference in behaviour in the 

 eclipse spectra of the enhanced and the strongest arc lines, two 

 separate lists of titanium lines have been made. The first, which 

 follows immediately, contains all the enhanced lines which occur 

 in Hasselberg's arc list, and the intensities of Professor Frost's and 

 the Kensington eclipse lines which correspond within 0*3 tenth-metre 

 are also given. 



* ' ICongl. Svenska Vefcenskaps Akad. Handl.,' vol. 28, No. 1, 1895. 



