250 



Mr. Albert Griffiths : Some 



The probable relation between i 2 and t when k is great, but 

 not infinite, is indicated in the figure below. 



Addendum II. 



The apparatus used as an interrupter is diagrammatically 

 sketched below. 



A C represents the vibrating wire, B the battery, D and E 

 electromagnets, F a vessel containing mercury, I the induction- 

 coil. Some cells, consisting of lead plates in dilute sulphuric 

 acid, were used as a shunt across the spark-gap ; they are not 

 shown in the figure, nor are they taken account of in the 

 theoretical considerations which are given below. 



It was found experimentally, as one would expect from 

 telephony, that initial magnetization by means of subsidiary 

 coils increased the amplitude of vibration, at any rate for low 

 frequencies. 



It was also found that a piece of iron placed below one of 

 the electromagnets increased the amplitude ; this is a corre- 

 sponding device to that used in Auer's telephone. The 

 probable explanation is that the iron produces a strong and 

 divergent field in the neighbourhood of the iron wire. 



