240 



PROCEEDINGS OP THE ABIERICAN ACADEMY 



Series X. 

 Magnetizing Current = 190 milliamperes. 



Series XII. 



Magnetizing Current — 259 milliamperes. 

 Line Current. Excursion. Line Current. 



3.77 98 2.29 

 3.23 83 1.87 



2.78 71 1.53 

 2.51 56 1.19 



Series XIII. 

 Magnetizing Current = 275 milliamperes. 



Series XIV. 



Magnetizing Current = 810 milliamperes. 



Line Current. Excursion. 



3.12 38 



2.87 28 



2.30 12 



Excursion. 

 47 

 34 

 23 

 16 



These figures show that the change in the amplitude of the vibra- 

 tion of the diaphragm is approximately proportional to the change in 

 strength of the line current within the limits of line current and 

 magnetizing current used, and with the distance ^ inch between the 

 core and diaphragm. Some irregularities in the figures are due to a 

 small variation in the strength of the magnetizing current, which was 

 furnished by a dynamo machine whose speed fluctuated a little. 



