116 PROCEEDINGS OF THE AMERICAN ACADEMY 



TABLE III. 



Core, Untempeeed Soft Steel. — Diaphragm, Disk of Ferrotype Iron, 



No. 31. 



An examination of Figure I, as well as of the various curves fol- 

 lowing it, will show that the effect of increasing the strength of the 

 magnet of the transmitter is in all cases to cause at first a rather rapid 

 increase of the strength of the induced current, which later increases 

 less rapidly, rising soon to a maximum value, from which it falls off, 

 at first rapidly, and afterwards more and more slowly as the strength of 

 the field is further increased. We proceed to consider the explana- 

 tion of these results. 



It is evident that three distinct sources of variation exist to affect 

 the current furnished hy a magneto transmitter as the strength of the 

 magnet is increased. First, the direct effect of the increased strength 

 of field in which the diaphragm moves is to increase proportionally the 

 strength of the induced current, since it increases correspondingly the 

 rate of change in the number of lines of force enclosed by the coil of 

 the instrument ; second, an approach toward saturation of the magnet, 

 so far as it alone is concerned, will tend to diminish the induced current, 

 on account of the smaller variation in the strength of the pole due to a 

 given motion of the diaphragm ; and, third, the nearer approach toward 

 saturation of the diaphragm will have the same tendency. 



The rapid rise in the induced current at the beginning is of course 

 due to the predominating influence of the increasing strength of the 

 field in which the diaphragm moves, as both core and diaphragm are 

 then but slightly magnetized. The subsequent changes in the current 

 must be explained by a consideration of the increasing magnetization 

 of either the core or the diaphragm, or both. 



It will be seen by comparing Tables I., II., and III., that the value 

 of the maximum induced current for a given excursion of the diaphragm 



