ATOMIC DISINTEGRATION MILLIKAN 281 



the mad, hot pace in the interiors of the suns. This discovery, or 

 suggestion, to account for the huge estimated stellar lifetimes, of 

 the complete annihilation of positive and negative electrons within 

 the nucleus, makes it unnecessary to assume, at least for stellar life- 

 time purposes, the building up of the heavier elements out of hydro- 

 gen. Indeed, it seems rather unlikely that both kinds of processes, 

 atom-building and atom-annihilating, are going on together in the 

 same spot under the same conditions; so we must turn to further 

 experimental facts to get more light. 



The ninth sign-post came into sight in 1927, when Aston made a 

 most precise series of measurements on the relative masses of the 

 atoms, which made it possible to subject to a new test the Einstein 

 formula for the relation between mass and energy, namely, E=Mg'. 

 This Aston curve is one of the most illuminating finger-pointings 

 we now have. It shows that : 



1. Einstein's equation actually stands the quantitative test for 

 radioactive or disintegrating processes right well, and therefore 

 receives new experimental credentials. 



2. The radioactive or disintegrating process with the emission 

 of an alpha ray must be confined to a very few heavy elements, since 

 these are the only ones so situated on the curve that mass can dis- 

 appear, and hence heat energy appear, through such disintegration. 



3. All the most common elements, except hydrogen, are already 

 in their most stable condition; that is, their condition of minimum 

 mass, so that if we disintegrate them we shall have to do work upon 

 them, rather than get energy out of them. 



4. Therefore, man's only possible source of energy other than the 

 sun is the upbuilding of the common elements out of hydrogen or 

 helium, or else the entire annihilation of positive and negative elec- 

 trons; and there is no likelihood that either of these processes is a 

 possibility on earth. 



5. If the foregoing upbuilding process is going on anywhere, the 

 least penetrating and the most abundant radiation produced by it, 

 that corresponding to the formation of helium out of hydrogen, 

 ought to be about 10 times as energetic as the hardest gamma rays, 

 that is, it ought to correspond to about twenty-seven million electron- 

 volts in place of two and a half million. 



6. Other radiations corresponding to the only other abundant ele- 

 ments, namely, oxygen (oxygen, nitrogen, carbon), silicon (mag- 

 nesium, aluminum, silicon), and iron (iron group), should be found 



