THE GASES OF THE ATMOSPHERE 147 



recent Table of the International Committee (1916), 

 namely A = 39*9, K = 39*l, the value for argon is too 

 high. It looks therefore as though this was an anomaly 

 similar to that which has for so many years been a 

 subject of repeated investigation, namely the relation 

 of tellurium (Te = 127'5) to iodine (I=126'92). 



As Ramsay remarks at the end of one of his papers 

 (Proc. Roy. Soc. 67, 333), "the conundrum of the 

 periodic table has yet to be solved." 



Of the companions of argon, neon, krypton and xenon 

 are found with it among the constituents of our atmo- 

 sphere. Helium, however, the lightest of them all, was 

 not at first detected in the air. notwithstanding repeated 

 experiments made by Lord Rayleigh and by Ramsay 

 with this object. It is, however, curious that helium 

 is found in connection with certain sources of hot 

 mineral waters, though not in all. Thus the water of 

 the geysers in Iceland contain not a trace, neither do 

 the waters of Harrogate and Strathpeffer, while the 

 springs at Wildbad, in the Black Forest, are said to 

 contain small quantities, and it has also been found in 

 the waters of Bath and Cauterets (Basses Pyrenees). 



Helium was recognised in the air much later by Baly 

 and others (Nature, October 1898). 



The late Dr. Johnstone Stoney, in discussing the 

 atmospheres of planets and satellites (Trans. Roy. 

 Dublin Society, 1897), expressed the view that the com- 

 position of the atmosphere composed of a mixture of 

 gases depends on the velocity of translation of the 



