240 



PROCEEDINGS OP THE AMERICAN ACADEMT 



In order to study the effect of the thickness of the diaphragm, fur- 

 ther measurements were made, using sheet iron diaphragms Nos. 21, 

 22, 23, 26, B. W. G., whose thickness was 0.032 in., 0.027 in., 0.024 in., 

 and 0.018 in., respectively. The results of these measurements will 

 be found in Tables IX. to XII. inclusive, and from them the Curves 

 21, Figure 2, and 22, 23, 26, Figure 3, were constructed. The 

 numbers attached to the curves indicate the gage of the diaphragm. 

 The curves numbered 3, 4, 5, 6, respectively, are constructed to 

 show the effect due to the addition of the diaphragm of thickness 

 indicated by the gage number, as already explained in the case of 

 Curve 2, Figure 2. 



Diaphragm, Sheet Iron, No. 21. 



Strength of Field. Induced Current. Strength of Field. Induced Current. 



.000 131.0 .437 121.7 



.073 130.2 .521 118.4 



.107 130.0 .649 111.3 



.167 129.7 .754 108.5 



.207 129.2 .933 100.2 



.257 128.0 1.07G 92.2 



.366 125.4 1.280 81.4 



