346 BOLTWOOD— RADIOACTIVITY. [April 22. 



theory of the constitution of matter. Unfortunately, so Httle weight 

 can be attached to these results and the conclusions reached by these 

 authors, that they have received no serious consideration from those 

 most competent to judge their value. 



In closing, a point which seems worthy of special emphasis may 

 be briefly mentioned. This is the apparently important part played 

 by the alpha or material particle emitted during radioactive trans- 

 formations. In those cases where it has been possible to observe 

 its influence, the loss of an alpha particle is always accompanied by 

 a corresponding decrease in the mass of the atom from which it is 

 separated. Although the disruption of a radio-atom is accompanied 

 bv the release of a relatively enormous amount of energy, still it 

 appears that the fragments projected into space are always of one 

 or the other of two quite distinct classes; either beta particles of 

 extremelv small mass, or helium atoms of a mass seven thousand 

 times that of the beta particles. So far as the results of our experi- 

 ments have enlightened us we have not yet been able to observe the 

 resolving of the by far the greater proportion of the effective mass of 

 an atom into anything other than a further subdivision of ordinary 

 matter. 



Yale University, 

 April 22, 1911. 



