ATOMIC THEORY AND RADIOACTIVITY 



By SIR OLIVER LODGE, F.R.S., D.Sc, LL.D. 



In the April number of Science Progress is an article on 

 11 The Mystery of Radioactivity," signed by the easily recog- 

 nisable initials H. E. A. ; and in spite of the eminent services 

 of the author of that article to Chemistry, I feel that some 

 notice ought to be taken of it because, as it stands, its tendency 

 is obstructive to progress. With " conservatism " I confess to 

 a good deal of sympathy, up to a limit, but the limit is trans- 

 gressed when facts are ignored and hypotheses wildly 

 manufactured in order to retain some old and superseded 

 exclusive and negative generalisation. 



That radium has proved itself an element, to be classed with 

 the other elements in respect of such things as a recognised 

 place in Mendelejeffs series, a definite spectrum, regular 

 chemical compounds, and such like, is surely a fact ; and to 

 controvert it needs something more than an etymological 

 discussion about the meaning of the word element. The term 

 would be equally applicable or inapplicable if, as has often been 

 surmised, all the known elements turn out to be groupings 

 of some one fundamental substance. What is certain is that 

 the so-called elements form a definite and recognised group 

 of substances of which radium is a member. 



Moreover, it must be permissible to speak of an atom of 



radium, when dealing with its physical and atomic properties, 



in spite of the fact that it is an atom liable to spontaneous 



explosion or fission. To hesitate about this — to be afraid to 



use the convenient and brief term " atom " because of historical 



derivation — would involve a loss of this useful word altogether. 



It is well known in philology that significance changes, and 



that the meaning associated with original derivation is liable 



to be gradually departed from. Besides, even pedantically, we 



must admit that the idea of " cutting " suggests something 



artificial, and that the artificial stimulation of atomic break-up 



has yet to be discovered. 



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