Lecture Experiments illustrating Syntony. 



285 



(2) L large, to obtain sharp resonance and large magnifi- 



cation-ratio. 



(3) S small, to obtain sharp resonance and to avoid large 

 sparks at ' make ' and ' break/ 



(4) Radius of sending and receiving coils large, to obtain 



large N. 



(5) The auxiliary coils must be suited to conditions (1) and 



(2), otherwise they may have any size or shape. 

 For the comparatively small frequency used, the self- 

 induction port of the impedance need not be con- 

 sidered. 



The Circuits. 



The sending-circuit is shown in the sketch (fig. 1), which is 

 in elevation. The current leaving the cells at the top end 



Fia-. 1 



passes through the key, fork, platinum-contact (P.O.), rheo- 

 stat, and to the lower end of the cells ; the fork is worked by 

 the passage of this current Ihrough the electromagnet between 

 the prongs of the fork. 



But there is another branch to the circuit, beginning at the 

 mercury-contact (M.C.), then through the coils Ci and C 2 , the 

 adjustable condenser S being put as a shunt to the two coils, 

 then to the lower end of the cells. 



Thus if S were removed we should obtain current-alter- 

 nations in the coils of the frequency (100) of the fork; but 

 with S in place, we have a frequency depending on the values 

 of L and S in the coils. In setting up the system we select 

 suitable coils and condenser, calculating the values of L 

 from the dimensions of the coils; then put in such a value of 



Phil, Mag. S. 5. Vol. 50. No. 304. Sept. 1000. X 



