50 THE NEW KNOWLEDGE. 



that this conductivity must be due to an actual some- 

 thing mixed with the gas, this something being removed 

 by filtration. 



It is also obvious that this something since the gas is 

 perfectly transparent must be in the nature of particles, 

 and that these particles, which, it must be remembered, 

 are conducting particles, must be different from' the par- 

 ticles, or molecules, of the gas in the normal state. The 

 further fact that these particles may be removed by mak- 

 ing the conducting gas traverse a space through which a 

 current of electricity is passing shows that the particles 

 must be electrified; and since, moreover, the conducting 

 gas as a whole shows no charge that these particles must 

 be both positive and negative. This latter fact is also 

 shown in Fig. 10, which illustrates the division of a flame 



Fig. 10. Showing the division of a flame into two parts by placing 

 it between oppositely charged plates. 



into two parts, one part positively and the other nega- 

 tively electrified, simply by placing the flame between two 

 oppositely charged plates. 



We have been led, then, to the discovery of certain elec- 

 trified particles in the conducting gas. These particles are 

 called ions, and the process by which the gas is made into 

 a conductor, the ionisation of the gas. 



