HERTZIAN WAVE ^YIRELESS TELEGRAPHY. 



115 



Fig. 9. Marconi-Beaun 

 System of inducing Eleo 

 TROMOTivE Force in an 



condenser through the primary coil of a transformer of a particular 

 kind, called an oscillation transformer (see Fig. 9). The spark balls 

 are brought within a few millimeters of each other. When the coil 

 is set in operation, the jar is charged and discharged through the spark 

 gap, and electrical oscillations are set up in the circuit consisting of 

 the dielectric of the jar, the primary coil of the oscillation trans- 

 former and the spark gap. The secondary cir- 

 cuit of this oscillation transformer is connected 

 in between the earth and the insulated aerial 

 wire; hence when the oscillations take place in 

 the primary circuit, they induce other oscillations 

 in the aerial circuit. But the arrangement is not 

 very effective unless, as is shown by Mr. Marconi, 

 the two circuits of the oscillation transformer are 

 tuned together. 



We shall return presently to the consideration 

 of this form of transmitter; meanwhile, we may 

 notice that by means of such an arrangement it 

 is possible to create in the aerial a far greater 

 charging electromotive force than would be the -A-erial a. b, battery ; k 



.J. ,1 -1 i. J T ;i . key, J, induction coil; S 



case II the aerial were connected directly to one spark gap ; c, Leyden jar ; 

 terminal of the secondary circuit of the induction ^' ^^^^^ p^*^^ = p*- osciua- 



. . , 1 . ^ , tion translormer. 



coil, the other terminal being to earth, and the 



two terminals connected as usual by spark balls. By the inductive 

 arrangement it is possible to create in an aerial electromotive forces 

 which are equivalent to a spark of a foot in length, and when the 

 length of the aerial is also properly proportioned, the potential along 

 it will increase all the way up, until at the top or insulated end of 

 the aerial it may reach an amount capable of giving sparks several 

 feet in length. From the remarks already made on the analogy be- 

 tween the closed organ-pipe and the Marconi aerial wire, it will be 

 seen that the wave which is radiated from the aerial must have a 

 wave length four times that of the aerial, if the aerial is vibrating in 

 its fundamental manner. It is also possible to create electrical oscil- 

 lations in a vertical wire which are the harmonics of the fundamental. 

 All musicians are aware that in the case of an organ-pipe, if the 

 pipe is blown gently it sounds a note which is called the fundamental 

 of the pipe. The celebrated mathematician, Daniel Bernouilli, dis- 

 covered that an organ-pipe can be made to yield a succession of 

 musical notes by properly varying the pressure of the current of air 

 blown into it. If the pipe is an open pipe, and if we call the frequency 

 of the primary note obtained when the pipe is gently blown, unity, 

 then when we blow more strongly, the pipe yields notes which are the 



