OF ARTS AND SCIENCES. 99 



determined by means of a ballistic galvanometer showed that the max- 

 imum motion of the diaphragm with a given value of the alternating 

 line current is reached before the core reaches half-saturation. 



An inspection of the curves also makes it plain that in general the 

 amplitude of vibration of the diaphragm increases less rapidly than the 

 current actuating the telephone. 



In the experiments previously described the strength of the magnet 

 was kept constant in each series, and the line current was varied. 

 A series of measurements was also made in which the strength 

 of the line current was kept constant, while the strength of the 

 magnetizing current was varied, which shows very clearly the man- 

 ner in which the amplitude of vibration changes with change in 

 the strength of the magnet. Table III. gives the results obtained. 

 The currents and amplitudes are given in terms of the same units as 

 heretofore. 



TABLE III. 



Current. Amplitude. 



35 5.0 



76 13.6 



149 20.5 



208 42.3 



256 60.8 



273 66.0 



302 84.5 



321 106.5 



352 111.5 



378 99.8 



398 89.6 



480 45.4 



560 28.0 



671 11.6 



780 8.5 



984 4.0 



1142 3.0 



Beyond the highest value given in the table, 1142 milliamperes, the 

 excursion seemed to remain almost constant, and of too small a 

 magnitude to be measured readily. 



Figure 2 illustrates graphically the results obtained. The ampli- 

 tudes of vibration are represented by the ordinates of this curve, while 

 the abscissas represent, in terms of an arbitrary unit, the strength of 

 the field at the diaphragm, as obtained from the previously constructed 

 curve of magnetization already referred to. 



