46 Mr. J. Liint. On the Origin of certain Unknovm 



and a subsequent photograph of the spectrum of € Canis Majoris, in 

 which the argon tube Avas used, as stated, as a comparison spectrum, 

 established their absolute identity both as regards position and relative 

 intensity. 



It was, therefore, evident that a terrestrial source of the three 

 unknown lines had been discovered, and with the behaviour of the 

 carbon dioxide tube fresh in mind, and the replacement of the argon 

 spectrum by unknown lines and those of oxygen by use of a highly 

 disruptive spark, it is not surprising that an obvious startling explana- 

 tion as to the nature of the element thus found terrestrially should have 

 suggested itself. 



It was at first assumed, erroneously as it afterwards proved, that the 

 origin of the unknown lines lay in the gaseous contents of the argon 

 tube. Four argon tubes in succession gave precisely the same results, 

 viz., the argon spectrum with an ordinary discharge and the unknown 

 lines and oxj^gen, together with the disappearance of the argon 

 spectrum, as a result of using the jars and air gap. On communi- 

 cating these results to Dr. Gill, he at once interested himself in the 

 matter, and gave every facility for a further prosecution of the inquiry. 

 He remembered that Professor Eamsay had fuinished him with a 

 specimen tube of pure argon, and this tube had not been examined. 

 On trying this tube under the same conditions as the others, it was 

 found to give the argon spectrum under all conditions. Neither the 

 unknown lines nor oxygen made their appearance, even when the most 

 intense disruptive spark available was employed. 



The first four tubes had aluminium electrodes, whilst Professor 

 Eamsay's tube had platinum electrodes, and was more vacuous and 

 much shorter. 



A pair of aluminium electrodes was then taken from a vacuum tube, 

 and a spark between the metal terminals in air was next examined, 

 with the result that the unknown lines were not found. A line 

 appeared very approximately in the same position as the strongest of 

 the three lines, but this was only one of the numerous air lines, and 

 was due to nitrogen (4552*6 Neovius). Therefore, the electrodes of the 

 argon tubes did not account for the unknown lines. 



On a further examination of the negatives, the H and K lines of 

 calcium were recognised in the spectra of the argon tubes subjected to 

 the highly disruptive spark, pointing to the fact that the lime of the 

 glass was being volatilised. 



This fact alone might account for the presence of the oxygen lines in 

 the spectra, and the materials of the glass were then suspected as being 

 the origin of the lines under consideration. 



A tube of pure helium, kindly furnished to Dr. Gill by Professor 

 Eamsay, was next examined, and, with much surprise, this was found 

 also to behave exactly as the first argon tubes had done. 



