236 ELEMENTS OF ELECTRICITY AND MAGNETISM. 



The a-rays and the /8-rays are deflected by the magnetic field 

 and by the electric field. The direction of the deflection of the 

 a-rays is in each case opposite to the direction of deflection of the 

 $-rays, and therefore it is known that the a-particles are positively 

 charged and that the /3-particles are negatively charged. The 

 7-rays are not deflected by a magnetic field or by an electric 

 field. 



The present hypothesis regarding radio-activity is that the atoms 

 of all substances are complex systems of excessively small particles 

 called electrons, the atom of each element being a characteristic 

 self-contained group or system of electrons in very violent orbital 

 motion. These systems of electrons (atoms) are supposed to be 

 to some extent unstable, and when instability occurs, the system 

 (atom) collapses into a new configuration and at the same time 

 expels one or more positively or negatively charged electrons or 

 groups of electrons which constitute the a-rays and the y3-rays. 

 According to this hypothesis the 7-rays consist of abrupt ether 

 waves which are produced by the sudden collapse of the atomic 

 structure when instability occurs.* 



A clear representation of the nature of a-, y3-, and 7-rays is 

 shown in Fig. 165. Imagine an atom of the radio-active material 

 to collapse at a given instant sending out a 7-wave, an a-particle, 

 and a /3-particle. The relative positions reached by the 7-wave, 

 the a-particle, and the /3-particle at a given instant are shown in 

 the figure. The a-particle is a large positively charged particle 

 and the /3-particle is a small negatively charged particle. 



135. Determination of velocity and mass of the particles which 

 constitute canal rays (or a-rays) and cathode rays (or /3-rays). 

 A narrow stream of rays from a radio-active substance may be 



* A very instructive discussion of the electron theory is given by Sir Oliver Lodge 

 in a book entitled Electrons, published by Geo. Bell & Sons, London, 1906. The 

 method of measuring the degree of radio-activity of a radio-active substance is explained 

 in Franklin, Crawford and MacNutt's Practical Physics, Vol. 2, pages 148-153. 

 An example of the study of a radio-active transformation, that is, of the change which 

 takes place in the radio-active substance, as a result of its radio-activity, is given in 

 Franklin, Crawford and MacNutt's Practical Physics, Vol. 2, pages 154 and 155. 



