276 PROCEEDINGS OF THE AMERICAN ACADEMY. 



been pointed out, more or less automatically regulated by the reac- 

 tion of the secondary oscillation on the primary circuit, but not en- 

 tirely so for low values of I. C. F. The second condition of syntony is 

 that the shape of the primary wave or current-rush must be such that 

 the resulting electromotive force impulses in the secondary circuit, 

 due to the different parts of the primary wave, bear the proper phase 

 relation to the secondary wave. With a fixed secondary circuit the 

 first condition can be obtained by varying the main current /o, or the 

 primary capacity Ci. The second condition of syntony can be estab- 

 lished by changing the primary inductance Xi. 



(3) Observations and Discussion of Results. 



The two conditions of syntony are illustrated by the curves of 

 Figures 5 and 6. In Figure 5 the full line curve gives the variations 

 of the secondary current, I^, plotted to an arbitrary scale, as the main 

 current, /«, is varied, and shows maxima and minima of Ii as the first 

 condition of syntony is more or less perfectly fulfilled. The dotted 

 disconnected lines give the maximum wave length readings of the wave 

 meter, excited by the primary discharge, as ordinates plotted to the 

 variable 7^. The third dot-and-dash curve is the wave meter reading 

 when the secondary circuit is open. This figure is a fair representation 

 of several curves taken under different but similar conditions. 



In explanation of Figure 5 attention is called to the following facts. 

 It is evident that if the potential to which the condenser is charged 

 is practically the same under all conditions, — and experiment shows 

 that this is approximately the case, — then with a given Ci, the number 

 of discharges per second in the primary circuit is roughly proportional 

 to the current /<,. This actual spark fi-equency produces in the wave 

 meter an effect corresponding to a wave of that frequency. This pri- 

 mary fundamental wave length, as it will be called, plotted to To would 

 give a curve of the general shape given by the dot-and-dash line in the 

 figure. When, however, the secondary circuit is closed the secondary 

 current exerts an equilibrating influence on the primary discharge, 

 helping it to occur, as has been stated, at a definite time in relation to 

 the secondary current, thereby forcing the primary circuit to operate 

 according to the short horizontal lines. For instance, by reference to 

 the figure it is seen that, for a supply current of 0.7 ampere, the 

 unforced primary fundamental wave length is 350 meters. The fre- 

 quency corresponding to this is about 860,000 per second, which means 

 that there are that number of primary discharges occurring per second. 

 When, however, the secondary circuit, having a natural wave length 



