238 BODIES SMALLER THAN ATOMS. 



weakor, and so on for divcr.s .succession, until the progression ends in 

 the l)iggest particles on which the operations in chemistry and the 

 colors of natural ))odies depend and which by adhering compose bodies 

 of a sensible magnitude." 



The reasoning we used to prove that the resistance to the motion 

 of the corpuscle depends only upon the density is onl}^ valid when the 

 sphere of action of one of the particles on a corpuscle does not 

 extend as far as the nearest particle. We shall show later on that the 

 sphere of action of a particle on a corpuscle depends upon the velocity 

 of the corpuscle, the smaller the velocity the greater being the sphere 

 of action, and that if the velocity of the corpuscle falls as low as 10'' 

 centimenters per second, then, from what we know of the charge on 

 the corpuscle and the size of molecules, the sphere of action of the 

 particle might be expected to extend farther than the distance l)etween 

 two particles, and thus for corpuscles moving with this and smaller 

 velocities we should not expect the density law to hold. 



EXISTENCE OF FKEE CORPUSCLES OR NEC4ATIVE ELECTRICITY IN METALS. 



In the cases hitherto described the negativel}'^ electrified corpuscles 

 had been obtained })y processes which require the bodies from which 

 the corpuscles are liberated to be subjected to somewhat exceptional 

 treatment. Thus in the case of the cathode rays the corpuscles were 

 obtained ])y means of intense electric lields, in the case of the incan- 

 descent wire by great heat, in the case of the cold metal surface by 

 exposing this surface to light. The question arises whether there is 

 not to some extent, even in matter in the ordinary state and free from 

 the action of such agencies, a spontaneous liberation of those cor- 

 puscles — a kind of dissociation of the neutral molecules of the sub- 

 stance into positively and negatively electrified parts, of which the 

 latter are the negatively electrified corpuscles. 



Let us consider the consequences of some such effect occurring in 

 a metal, the atoms of the metal splitting up into negatively electrified 

 corpuscles and positively electrified atoms, and these again after a time 

 recombining to form neutral system. When things have got into a 

 steady state the number of corpuscles recombining in a^iven time 

 will be equal to the numl:)er liberated in the same time. There will 

 thus be diffused through the metal swarms of these corpuscles; these 

 will be moving about in all directions, like the molecules of a gas, and, 

 as they can gain or lose energy by colliding with the molecule of the 

 metal, we should expect by the kinetic theory of gases that they will 

 acquire such an average velocity that the mean kinetic energy of a 

 corpuscle moving about in the metal is equal to that possessed by a 

 molecule of a gas at the temperature of the metal. This would make 

 the average velocity of the corpuscles at 0° C. about 10^ centimeters 

 per second. This swarm of negatively electrified corpuscles when 



