PROCEEDIN(;S OF THE OHIO ACADEMY OF SCIENCE. 339 



Soddy has pro\ed this to be a fact. Again, since lead is always 

 persistently associated, in definite relative quantities, with radium 

 and uranium, it has been plausibly suggested, and the accumu- 

 lated evidence for the suggestion is becoming very strong, that 

 lead, if not a final disintegration product of the series, is prac- 

 tically such a product, itself disintegrating perhaps, but at a rate 

 which can only be estimated in millions of years. 



It is to be remembered that these changes are atomic, not 

 molecular, that they have to do with the nature of the so-called 

 elementary substances. Lord Kelvin, addressing the chemical 

 society in 1907, a few months before his death, suggested that 

 the name atom ought to be abandoned, as inappropriate to a 

 thing which could be broken, and proposed for discussion the 

 question, " when is an atom not an atom?" In fact, the real 

 difiference between an atom and a molecule seems now to be 

 that we can break up a molecule into its constituent elements by 

 chemical processes, but that we are not masters of such stores 

 of energy as will enable us to tear apart the atom into its sub- 

 elements. 



Before Roentgen's discovery of the X-Rays had drawn 

 universal attention to radiation problems, the passage of elec- 

 tricity through gases had been made the subject of much study, 

 aroused chiefly by the fluorescent and other effects opposite the 

 cathode. Plucker and Hittorf, Goldstein and Crookes had made 

 many ingenious experiments and established many interesting 

 facts, eventuating finally in a lively discussion as to the nature 

 of the cathode rays. It was J. J. Thomson, now Sir Joseph, 

 who in 1897. deflecting the rays for the first time by both an 

 electric and a magnetic field, was able to infer with great proba- 

 bility that he had to do with a stream of electrified particles 

 rather than with a system of ether-waves. He explained their 

 passage through metals, shown by Hertz and Lenard, by suggest- 

 ing that they were of sub-atomic size, and, by using fields of 

 definite strength found not only their velocity, but the important 

 ratio, m/e, between the mass of the flying particle and the elec- 

 tric charge which it carried. By a daring extension, due to C. 

 T. R. Wilson, of Aitken's method of counting the fog-globules 



