explain the Radioactivity of Radium. 315 



§ 8. Go back to the ''equilibrium o£ temperature" reached 

 at the end of § 3. Suppose the matter around the Radium to 

 be a globe of lead of 50 cms. radius, surrounded by a spherical 

 sheath so arranged as to let a stream of water flow steadily 

 along meridional semicircles of the globe. Every " a particle," 

 and " j3 particle," shot from the Radium into the lead, will 

 generate the heat-equivalent of its kinetic energy in the 

 lead. A certain proportion of the heat will pass inwards 

 into the Radium to cooperate with radiation in supplying 

 enerov for the continued loadings. The remainder will be 

 conducted outwards and will be carried away by the water. 

 The arrangement suggested will form a calorimeter to measure 

 the steady, permanent, thermal, effect of Radium. 



§ 9. If the outer surface of the lead were coated with an ideal 

 impermeable varnish, the whole heat generated in the lead bv 

 the electrions and atoms shot out from the crystal, would 

 return into the crystal by conduction and would supply the 

 enerov for the loadings. 



§ 10. It has occurred to many radioactive minds, that by 

 making the lead globe large enough the heating effect might 

 possibly be all lost. This is no doubt true, according to the 

 explanation of radioactivity now suggested : because, with 

 thicker and thicker lead, a greater and greater proportion of 

 the heat generated in the lead will be conducted inwards to 

 supply the energy for the loadings in the crystal. 



§ 11. If the Radium is sealed in a glass tube or globe, and if 

 its heating effect is tested by a stream of water, flowing around 

 it through a glass tube of small bore, a large proportion of 



