912 



Dr. Marine Siegbahn on the Use of the 



employed telephone-membrane ; this value has later on been 

 verified by new measures. The difference between it and 

 the theoretical value of 23, for the ordinary oscillograph, is 

 remarkable, and gives rise to doubts as to the possibility of 

 using the telephone for oscillographic purposes. 



As a theoretical investigation is out of the question, owing 

 to the complicated nature of the phenomenon, we will give 

 some experimental facts, which may serve to throw light on 

 the problem. 



4. The Reproduction of the Currents through the Telephone 

 in more simple cases. 



In figs. 3-11 some oscillograms are shown, taken by the 

 method described above. 



Figs. 3 (PI. XVI.) and 4 give the swinging-curve of the 

 membrane when the curve suddenly changes from one constant 

 value to another; the correct reproduction would then consist 



Fisr. 4. 



of three straight lines, but, as shown in the figure, only the 

 free vibrations of the membrane occur. For such rapid 

 variations the telephone as registering instrument is out of 

 the question. 



As the next example, the reproduction of the primary 

 current in an induction-coil with a rotating interrupter is 

 shown in figs. 6-9. The real current-curve (fig. 5) was in 



Fur. 5. 



this case of the ordinary type of mechanical interrupters, as 

 was controlled by a Brauir's tube. The telephone-membrane 

 registers such a curve with a series of overlapped^ free 

 vibrations. Thus in this case the obtained curve gives no 

 true copy of the real curve. 



