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SCIENCE PROGRESS 



of certain elements, their sequence following in general the 

 periodic system, so the abundance of terrestrial elements may 

 indicate the earth's stage of evolution ! Where is the evidence 

 that the chemical properties and physical characteristics of 



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what we call to-day, e.g., sodium was the same eons ago, and will 

 be the same eons hence ? ' Where is the evidence that our life 



1 " Old Age of Chemical Elements," Science, N.S., vol. xlix, 1919, p. 328 ; 

 '' A Possible Source of Cosmical Energy," Science, N.S., vol. 1, 1919, p. 252, 



