240 SCIENCE PROGRESS 



Strutt points out that in no case does any mineral contain 

 more than a trace of helium unless thorium is also present. 

 When much helium is present, thorium is present in quantity ; 

 but the converse is not true, as is shown by the case of orangite. 



Later he quotes the case of the mineral fluorite, from Ivigut, 

 Greenland, which yields 27 c.c. of helium per kilogram, contains 

 scarcely any radium, but is rich in thorium. He concludes that 

 the production of helium from thorium must be considered to be 

 established. 



Note must be made in passing of the peculiar fact that pitch- 

 blende and cupro-uranite, two of the most strongly radioactive 

 minerals known, yield only minute traces of helium. 



In a paper published in the present year Strutt tabulates his 

 results for a very large number of minerals, which were examined 

 in order to observe whether (a) the degree of radioactivity is 

 sufficient to account for the quantity of helium present, (b) argon 

 and neon are present in definite amount. 



He finds that helium is present in almost all the minerals of 

 the earth's crust, and is roughly proportional to the traces of 

 uranium and radium they contain. When there is much more 

 helium than would be expected from the amounts of uranium 

 and radium present, it can always be connected with the presence 

 of thorium, with one exception. There is no evidence that 

 helium is produced from ordinary elements. 



The mineral beryl contains abundance of helium, but is only 

 very slightly radioactive. The helium cannot be connected with 

 any known constituent of beryl. 



With regard to argon, its presence in small quantities is 

 probably due to traces of atmospheric air leaking into the 

 apparatus. Nevertheless it is certainly present in igneous rocks, 

 and probably in siliceous minerals generally. No definite con- 

 clusion is reached with regard to the presence of neon. It 

 has been observed in several cases ; but Strutt states that an 

 admixture of one cubic centimetre of air makes the neon 

 spectrum visible, and that it may even be seen with one-tenth 

 of a cubic centimetre. 



The general results derived from the examination of the 

 gases from springs lead to the conclusion that they are all more 

 or less radioactive, and all contain traces of the rare gases. This 

 is only to be expected in the light of Strutt's results with minerals, 

 through some of which the spring waters must percolate. 



