114 G. F. BECKER RELATIOKS OF RADIOACTIVITY TO COSMOGONY 



-n-orld a dozen j-ears ago. They were studied on the theoretical side by 

 Mr Lorentz and Mr Larnior, and on the experimental as well as the 

 theoretical side by Mr J. J. Thomson. These investigations have estab- 

 lished that the atom is in fact extremely complex, consisting of corpuscles 

 or electrons, which seem to have a constant mass from whatever substance 

 they may be produced, this mass being about the one-thousandth part of 

 that of an atom of hydrogen. The electrons always carry a negative 

 charge of electricity. In an electrically neutral atom the electrons are in 

 rapid, gyratory motion, the details of which are at least as complex as 

 tliose of the planets in the solar system, and they are held together by a 

 positive electric charge equal to the sum of the negative charges carried 

 by the electrons. The electrons seem to have the same mass and charge 

 as ions and to be identical with them.^ 



This electronic theory of matter, which rests on a solid basis of experi- 

 ment, almost implies the possibility of disintegrating atoms. To provide 

 for atomic stability the electrons in the atom must describe orbits such 

 that the system is absolutely conservative, losing no energy whatever. 

 The smallest dissipation of energy must eventually lead to disruption. 



In pi;rsuing the study of the Roentgen rays the famous French physi- 

 cist, Mr Henri Becquerel, accidentally discovered a new species of rays 

 known by his name. The effect produced by the Becquerel rays is radio- 

 activity. He made this discovery in experimenting with pitchblende, or 

 impure uraninite, and at his .suggestion the properties of this mineral 

 were investigated by Mr and ]\Irs Curie, who detected in it the new 

 element radium. 



They found that this element was present in very minute amounts in 

 pitchblende, and that it emitted Becquerel rays in vastly greater quanti- 

 ties than pitchblende or than uranium. This emission proved to be an 

 atomic property, depending, not on the state of combination, but solely 

 on the amount of the element present. With Laborde, Mrs Curie showed ^ 

 that radium is continuously losing energy at an astonishing rate, so that 

 one gram of radium would spontaneously raise the temperature of 100 

 grams of water one degree in one hour. Here, then, is an actual case of 

 an unstable atom undergoing resolution into something else, and there- 

 fore into at least two other atoms. In 1903 Messrs Eutherford and 

 Soddy * suggested that helium might be one of the products, and in 1903 

 Messrs Eamsay and Soddy ^ demonstrated that helium was given off by 



= J. J. Thomson : Electricity and matter, 1904. 

 3 Comptes Rendus, vol. 136, 1903, p. 673. 



* E. Rutherford : Radioactive transformation, 1906, p. 181. This work has been my 

 main authority in the preparation of these notes. 

 5 Nature, vol. 68, 1903, p. 246. 



