A HISTORY OF SCIENCE 



lively charged electron revolving round an atom of 

 mass relatively large but having an equal positive 

 charge and held in equilibrium by electrical forces. 

 This system will radiate energy, and since the radiation 

 of energy is equivalent to motion in a resisting medium, 

 the particle tends to move towards the centre and i'ts 

 speed consequently increases. The rate of radiation 

 of energy will increase rapidly with the speed of the 

 electron. When the speed of the electron becomes very 

 nearly equal to the velocity of light, according to 

 Lodge, the system is unstable. It has been shown that 

 the apparent mass of an electron increases very rapidly 

 as the speed of light is approached, and is theoretically 

 infinite at the speed of light. There will be at this stage 

 a sudden increase of the mass of the revolving atom, 

 and, on the supposition that this stage can be reached, 

 a consequent disturbance of the balance of forces hold- 

 ing the system together. Lodge considers it probable 

 that under these conditions the parts of the system 

 will break asunder and escape from the sphere of one 

 another's influence. 



"It is probable," adds Rutherford, "that the pri- 

 mary cause of the disintegration of the atom must be 

 looked for in the 1 ss of energy of the atomic system 

 due to electro-magnetic radiation." 12 



Several methods have been devised for testing the 

 amount of heat given off by radium and its com- 

 pounds, and for determining its actual rise in tempera- 

 ture above that of the surrounding atmosphere. One 

 of these methods is to place some substance, such as 

 barium chloride, in a calorimeter, noting at what point 

 the mercury remains stationary. Radium is then in- 



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