128 PHYSICS OF THE ELECTRON 



of the substance, represents the emissive power of the radiation 

 integral, which bolometric measurements give directly. 



Now this ratio can be calculated, as Lorentz has shown, for wave- 

 lengths which are long in comparison with the mean path of free 

 electrons in the metal, as a function of the charge carried by each 

 of them. The comparison of these results with those of Kurlbaum 

 furnishes an entirely new method of obtaining this charge, and gives 

 3.7X1(T 10 E. S. units. 



(10) The Kinetic Theory. Finally, the last confirmation, which 

 states more precisely still our knowledge of the electric atom, and 

 our confidence in this fundamental idea, Townsend, through com- 

 paring by the simple reasoning of the kinetic theory the velocities of 

 ions in a gas under the action of an electric field with their coefficient 

 of diffusion through the interior of the gas, two quantities directly 

 measurable by experiment, has been able to demonstrate the identity 

 of the charge of one of these gaseous ions with the electric atom of 

 Helmholtz, the charge of a monovalent atom in electrolysis. 



From this comes directly a new confirmation of the values pre- 

 viously obtained, for it allows us to know, owing to Townsend's 

 results, the charge on an atom in electrolysis, and from it to deduce 

 immediately the constant of Avogadro, the number of molecules 

 contained in a given volume of a gas. The results are well in agree- 

 ment with the values of this constant (in general a little greater), 

 which we can directly deduce from the kinetic theory of gases. 



Here is an important group of concordant indications, all of abso- 

 lutely distinct origin, which show without doubt the granular struc- 

 ture of electric charges, and consequently the atomic structure of 

 matter itself. The measurements which I have just enumerated 

 allow us to establish, in great security, the hypothesis of the exist- 

 ence of molecular masses. 



I seek to point out here this extremely remarkable result, which 

 belongs without doubt to some fundamental property of the ether 

 and of the electrons, that all these electrified centres, whatever may 

 be their origin, are now identical from the point of view of the 

 charge which they carry. 



It is necessary for us to penetrate further into their properties, 

 into their relations with material atoms, to determine their relative 

 sizes, in order to add among others to the more exact ideas which we 

 possess in this field, that the electrons, or negative cathode cor- 

 puscles, are all identical not only from the point of view of their 

 charge, but also from the point of view of their dynamic properties 

 and of their masses. We are unhappily not so well informed in 

 regard to the positive centres. 



