aval RATE OF EMISSION OF ENERGY 165 
experiments (about 5°/.), no difference in the heat emission was 
observed in the two cases. The only difference between the 
experiments (1) and (2) is that in the latter the 8 rays are absorbed 
in the lead and add their heating effect to the radium. Since, 
however, the energy of the @ rays is probably not more than 1 °/, 
of that due to the a rays (section 103), no appreciable difference is 
to be expected. The experiments of Runge and Precht are quite 
consistent with the view that the heating effect largely depends on 
the energy of the @ rays. 
A further discussion of the heating effect of the emanation and 
of its secondary products is given in sections 163 and 181. 
