PROBLEMS OF MODERN SCIENCE 



Rutherford has already obtained some measure 

 of an answer to the first of them. We have seen 

 that under bombardment by a particles there is 

 evidence that the atoms of oxygen and nitrogen 

 give off bodies of mass 3 and charge 2 units. If 

 the mass of these nuclear fragments has been 

 correctly determined, an elementary calculation 

 shows that they possess more kinetic energy than 

 that of the particles which stimulated their 

 ejection. It thus appears that without making 

 any allowance for the energy left in the a particle 

 and in the residue of the disrupted atom, the 

 process involves the tapping of energy from a 

 source within the disrupted nucleus, and the ratio 

 of this gain of energy to the amount of matter 

 involved in the process is of the same order of 

 magnitude as in the spontaneous radioactive dis- 

 integrations. Owing to the high importance of 

 this result, it is necessary that it should be estab- 

 lished beyond the possibility of doubt. This, I 

 think, can hardly be held to have been done. The 

 evidence is based on measurements of the range of 

 the ejected particles (i.e., the distance they can 

 travel in air without being stopped) and of their 

 deviation by a magnetic field. The combination 

 of these two measurements determines the ratio 

 of the square of the mass of the fragments to their 

 electric charge to within perhaps ten per cent., 

 but there are no measurements which give these 

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