134 Mr. J. Norman Lockyer. On the unknown 



In each case in which K was present, the micrometer scale was set 

 to the reading for this line, and the photograph to be reduced then 

 adjusted until the K line was under the cross-wires of the micro- 

 meter. Each line in the spectrum was then in turn brought under 

 the cross-wires, and the micrometer readings noted. The corre- 

 sponding wave-lengths were then read off from the curve, and in 

 this way, lists of the wave-lengths of the lines in the various spectra 

 were compiled. These lists were then all thrown together into one 

 table, giving the wave-lengths and intensities of all the lines recorded, 

 and the spectra in which they appear. 



For the wave-lengths thus obtained no greater accuracy than one 

 indicated by four figures is claimed. It was my intention in the first 

 instance to give five figures from the more elaborate tables of some 

 of the elements given by other observers, but this had to be 

 abandoned in consequence of the considerable variations found in the 

 tables between the results as given by different observers. 



First, as regards the gas from eliasite. The following list gives 

 the lines obtained in the complete inquiry after the lines due to the 

 old gases have been eliminated. It should be stated, however, that 

 several of the lines have wave-lengths very near those of the old 

 gases ; these have been retained when the more intense lines of the 

 old gases are absent from the spectra. These cases are pointed out 

 in the table. 



In the case of some of the lines in the visible part of the spectrum, 

 more accurate wave-lengths have been recorded "by means of a four 

 prism Steinheil spectroscope. These lines are indicated by (s). 



Attempts have been made to concentrate the eliasite gas by the 

 process of sparking with oxygen over potash, but the quantity of gas 

 remaining is so small, and so largely admixed with helium and argon, 

 that a new research, using very much more material, is essential. 



It should be remarked that the list of lines which have been 

 observed and photographed in the spectrum of the gases from 

 eliasite represents the results of several experiments which have 

 been made with different samples of the mineral. Some of the lines 

 have only been seen once, while others have been noted several 

 times. This suggests that the origins of the lines are very diverse, 

 and it seems probable that some constituents of the mixture of gases 

 obtained are absorbed by the potash in the process of sparking. 



Next, with regard to the other minerals already examined. As it 

 is impossible for me to go on with this research for the next few 

 months, it seems desirable, in the interest of other workers, to give 

 at the same time a complete list of the unknown lines, so far as the 

 observations have at present gone, indicating their mineral origins, 

 and whether or not lines nearly coincident in position have been 

 observed in any celestial body. 



