Manchester Memoirs, Vol. xlviii. (1904), No. 8. 31 



of volume of the emanation with time is by no means 

 uniformly observed, and it would appear that different 

 kinds of glass act differently. In some it would appear 

 that the helium after penetrating the glass slowly 'soaks' 

 out of it without the assistance of heat. These points are 

 under examination, and the results described must be 

 understood to be of a more or less preliminary character. 

 As soon as it was realised that the radio-activity of a 

 powerful element like radium is due to an insignificant 

 fraction of the total number of atoms breaking up in the 

 unit of time, it was evident that the internal energy bound 

 up in the structure of an atom and released when it 

 disintegrates is enormously greater than is ever associated 

 with molecular structure. This view may be said to be 

 experimentally proved by some recent work of Professors 

 Rutherford and Barnes^ on the heat emitted by the radium 

 •emanation. They found that if the emanation is released 

 from a solid radium compound by heat, and condensed in 

 a glass tube by means of liquid air, the heat-emission 

 from the radium is much reduced, while the greater part 

 is now emitted from the emanation. This result follows 

 directly from the disintegration theory. Since only about 

 one-fourth of the a particles expelled are derived from the 

 initial disintegration of the radium, and three-fourths from 

 the subsequent disintegrations of the emanation, it follows 

 that when the emanation, etc., are removed the heating 

 effect of the radium should be reduced to one-fourth the 

 initial value, while the emanation, etc., should give three- 

 fourths of the initial value. Hence the equilibrium 

 amount of the emanation in one gram of radium emits 75 

 gram-calories of heat per hour. The total quantity of 

 heat emitted during its complete life is given by multiply- 

 ing the emission per hour by the average life of the 

 ^ Phil. Mag., 1904, S.6, v. 7, p, 202. 



