OF ARTS AND SCIENCES. 117 



is approximately the same with all the three cores used, and that the 

 same is true as to the strength of field corresponding to this maxi- 

 mum current. Moreover, saturation curves constructed for the several 

 cores showed that in all cases the magnet was still very far removed 

 even from half-suturation when the maximum induced current was ob- 

 tained. From these facts it appears that the degree of saturation of 

 the magnet is practically unimportant, so far as the general results 

 shown in Figure 1 are concerned. 



It remains to observe the part played by the increasing magnetiza- 

 tion of the diaphragm. Other things remaining the same, as this ap- 

 proaches more and more closely towards saturation the increase in the 

 number of lines of force passing between it and the magnet on the 

 approach of the diaphragm to the magnet must become smaller and 

 smaller, and this change will tend to oppose the effect of the increased 

 absolute strength of the magnetizing force. The small mass of the 

 diaphragm will evidently cause it to show the effect of an approach to 

 saturation while the core is far below that condition. And such an ac- 

 tion will clearly explain the observed changes in the current strength. 



In order to test this matter still further, the experiment was tried of 

 varying the mass and material of the diaphragm. 



The results are shown by the curves in Figures 1, 2, and 3, which 

 are constructed from the data given in Tables I. to X. ; further results 

 of the same character are given in Tables XI. and XII. 



TABLE IV. 



Core, Norway Iron. — Diaphragm, Two superposed Disks of Ferrotype 



Iron, No. 31. 



