Loiv Frequency and their Resonance. 515 



large alternator. The impressed e. m. f. was maintained 

 constant and equal to about 1000 volts. The frequency was 

 also maintained constant and equal to nearly 125 periods per 

 second, hence just about \ of the frequency obtained by the 

 small machine. The secondary was now tuned first when there 

 was no iron wire core in the inertia coil. The condenser 

 potential rose steadily until the maximum point was reached. 

 There was no sign of an upper harmonic. This distressed me 

 very much in view of the statement which I made in my last 

 article concerning the presence of upper harmonics in the 

 e. m. f. generated by this alternator. I had evidently blun- 

 dered somewhere in my previous experiment with the large 

 alternator. In my endeavors to locate the blunder I discovered 

 a very peculiar behavior of the iron when it is under the 

 inductive action of a resonant circuit, which behavior ex- 

 plained to me perfectly why in the experiment, which I 

 described in my last paper,* there was a much higher rise of 

 potential when the capacity was considerably increased without 

 apparently increasing perceptibly the coefficient of self- 

 induction. 



Experiment %. — I next placed the iron wire bundle into the 

 inertia coil and found that the maximum rise was one half 

 of the rise which was obtained without the iron, which showed 

 that with the diminution of the frequency the damping effect 

 of the iron upon resonance was much less. If a high impressed 

 e. m. f is employed in the resonant circuit just described 

 then the rise of potential can be made even higher with iron 

 than without it at this frequency . Increasing the capacity 

 considerably and then raising the wire bundle until the maxi- 

 mum deflection in the Thomson voltmeter was obtained 1 

 found that only a slight displacement of the bundle was neces- 

 sary to reach the point of resonance. The maximum voltage, 

 or the resonant rise, was considerably higher. (It will be seen 

 presently that under certain conditions the bundle can be 

 lowered again without destroying resonance or diminishing the 

 resonant rise and it was owing to this circumstance that in the 

 experiment described in my last paper I believed that I was 

 tuning the circuit to respond to an upper harmonic of the 

 impressed e. m. f.) 



Increasing the capacity again and then raising the iron 

 wire bundle a little more the maximum potential was again 

 increased until a point was reached at which the maximum 

 rise of potential began to diminish when the capacity was 

 increased and the iron wire bundle raised in order to establish 

 resonance again. From this point on, which I shall call the 



*This Journal, May, 1893, pp. 426, 427, 429. 



