HERTZIAN WAYE WIRELESS TELEGRAPHY. 



109 





Fig. 6. (a) Distribution 

 OF Electric Pressure in a 

 Marconi Aerial A, (b) Dis- 

 tribution OF Electric 

 Current in a Marconi 

 Aerial, as shown by the 



along the aerial by the ordinates of a dotted line so drawn that its dis- 

 tance from the aerial represents the potential oscillation or current 

 oscillation at that point (see Fig. 6). 



This distribution of potential and current along the wire does not 

 necessarily imply that any one electron moves far from its normal posi- 

 tion. The actual movement of any particular 

 air molecule in the case of a sound wave is prob- 

 ably very small, and reckoned in millionths of 

 an inch. So also we must suppose that any one 

 electron may have a small individual amplitude 

 of movement, but the displacement is transferred 

 from one to another. Conduction in a solid may 

 be effected by the movement of free electrons 

 intermingled with the chemical atoms, but any 

 one electron may be continually passing from a 

 condition of freedom to one of combination. 



So much for the events inside the wire, but 

 now outside the wire its electric charge is repre- 

 sented by lines of electric strain springing from 

 the aerial to the earth. It must be remem- 

 bered that every line of strain terminates on ordinates of the dotted 



TT 1 1 Link xy. 



an electron or a co-electron. Hence when the 



discharge or spark takes place between the spark balls, the rapid move- 

 ment of the electrons in the wire is accompanied by a redistribution and 

 movement of the lines of strain outside. As the negative charge flows 

 out of the aerial the ends of the strain lines abutting on to it run down 

 the wire and are transferred to the earth, and at the next instant this 

 semi-loop of electric or ether strain, with its ends on the earth, is 

 pushed out sideways from the wire by the growth of a new set of lines 

 of ether strain in an opposite direction. The process is best under- 

 stood by consulting a series of diagTams which represent the distribu- 

 tion and approximate form of a few of the strain lines at successive 

 instants (see Fig. 7). In between the lines of formation of the suc- 

 cessive strain lines between the aerial and the earth, corresponding to 

 the successive alternate electric charges of the aerial with opposite 

 sign, there are a set of concentric rings of magnetic flux formed round 

 it which are alternately in opposite directions, and these expand out, 

 keeping step with the progress of the detached strain loops and having 

 their planes at right angles to the latter. As the semi-loops of electric 

 strain march outwards with their feet on the ground, these strain lines 

 must always be supposed to terminate on electrons, but not continually 

 on the same electrons. Since the earth is a conductor, we must sup- 

 pose that there is a continual migration of the electrons forming the 



