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PROCEEDINGS OF THE AMERICAN ACADEMY 



TABLE I. 



It appears from these results that with the magneto-receiver now 

 used the change in the amplitude of the vibration is approximately 

 proportional to the change in strength of the current for the stronger 

 currents used in the measurements, but with the weaker currents the 

 amplitude increases at a more rapid rate. These currents as a whole, 

 however, are higher than those reached in practice. 



In subsequent experiments we used as a receiver the electro-mag- 

 netic telephone previously mentioned. The end of its core was set 

 at a distance of -^ inch from the diaphragm. With the undulatory 

 current in the line coil maintained at a constant value in each sepa- 

 rate series of experiments, while the magnetizing current was varied, 

 results were obtained as shown in Table II. Line currents with 

 values successively varied in the different series were produced by 

 the microphone transmitter. The values of the magnetizing currents 

 in milliamperes are given in the first column, the corresponding excur- 

 sions of the diaphragm in terms of one division of the micrometer in 

 the second. Series I., III., V., and VII. are represented by the curves 

 in Figure 2. 



The results reached agree very well with those obtained by Cross 

 and Mansfield, when currents from an alternating dynamo were used, 

 except that in these last the maximum value of the excursion was 

 reached with a magnetizing current of 320 milliamperes, while with 

 those obtained in the present investigation the maximum value was 



