Lecture Experiments illustrating Syntony. 



287 



Now put in the first relay by adjusting the carbons at M x . 

 The action occurring- at M a and M 2 must be explained in 

 detail. The coil M x lies in a horizontal annular space in which 

 the lines of force run radially, and normal to the wires in the 

 coil ; then if current-alternations occur in the coil, it is im- 

 pelled up and down with the frequency of the alternations ; the 

 field meanwhile is maintained constant by a separate strong 

 current (say 10 amps.). The movements of the coil will, by 

 the action of the microphone, produce alternating currents of 

 a higher order of intensity in the relay-coil M 3 ; and this, 

 in turn, will in like manner give strong currents in the last 

 circuit, producing a loud note in the loud-speaking receiver 

 (L.S.R.). Although, to avoid confusion in the diagram, no 

 such connexions are shown, it is easy to put the induction-coil 

 and telephone (I.C. and T.) into the second circuit, and by 

 them adjust the working of M 1 to a maximum intensity. 



The relays should be guarded from all vibrations by being 

 put on blocks resting on soft rubber balls ; also they should 

 be on separate blocks, otherwise the action of one will start 

 the other. 



Description of the Relay. 



The principle involved is due to Prof. Lodge, and is found 

 in his magnifying-telephone ; but the attachments of the coil 

 and the system suspending it are due to the author, and will 

 be shortly described. 



Fia-. 3. 



The wires WW (fig. 3) carry the strong current (say 

 10 amps.) used to produce a field ; the magnetic circuit of 



X2 



