Helium in the Classification of Elementary Substances. 3 



On Helium and its place in the Natural Classification 

 of Elementary Substances. By Henry Wilde, F.R.S. 



(Received October 1st, 1895.) 



The announcement made by Professor Ramsay that a 

 gas from the mineral Cleveite showed the yellow spectral 

 line of solar helium A 5876, and was therefore identical 

 with that hypothetical element,* was received by physicists 

 with some amount of incredulity, as it was illogical to 

 predicate the identity of any element from the near 

 coincidence of a single line among the numerous lines 

 which belong to other elementary substances in the 

 gaseous condition. Nevertheless, the conspicuous bright- 

 ness and comparative isolation of the chromospheric line 

 D 3( together with the statement by Crookes, that the 

 yellow line of the cleveite gas was single, f in agreement 

 with the reputed singleness of D 3) gave some force to 

 the idea that the solar and terrestrial gases were identical. 

 Lockyert and Runge,§ however, subsequently discovered 

 that the yellow line of the new gas was double, and the 

 latter observer justly remarked "that the unknown element 

 helium, causing the line D 3 to appear in the solar spectrum, 

 is not identical with the gas in cleveite unless D 3 is also 

 shown to be double." Runge further observed that the 

 less refrangible of the two lines was much weaker than 

 the other, and he found the difference in the wave-lengths 

 of the lines to be 0323 tenth metres. 



* Chemical News, March 29, 1895. 

 t Chemical News, March 29, p. 151. 

 J Proc. Roy. Soc, April 25, p. 69. 

 § Nature, June 6, p. 128. 



