122 future's dfctracles. 



rent. In the latter case one tone has to be 

 superposed upon another and must be trans- 

 mitted with a varying but a continuously 

 closed current. I make a distinction between 

 a closed circuit and a closed current. In the 

 case of the arc-light the circuit is open (that 

 is, broken), technically speaking, but the cur- 

 rent is still flowing. The reason why the 

 Reiss and other metallic contact telephone 

 transmitters cannot successfully be used for 

 telephone purposes is that metal points will 

 not allow of sufficient separation of the trans- 

 mitting points without breaking the current 

 as well as the circuit. Carbon contacts admit 

 of a much wider separation without actually 

 stopping the flow of the current, which latter 

 is a necessity for perfect telephonic transmis- 

 sion, and it was the use of carbon that made 

 that form of transmitter a success. 



There are other forms, or at least one other 

 form that does not depend upon the length of 

 the voltaic arc formed when the electrodes are 

 separated. Of this we will speak another time. 

 Now let us go back to the domestic incident 

 referred to above. 



One evening in the winter of 1873-4 I came 

 home from my laboratory work and went into 

 the bathroom to make my toilet for dinner. I 

 found my nephew, Mr. Charles S. Sheppard, 

 together with some of his playmates, taking 

 electrical " shocks " from a little medical in.- 



