Multiple Cransmtesfon. 



denser, with the many leaves of tin-foil, sup- 

 plies the greater metal surface to be traversed 

 liy the short line current, causes the flow to be 

 equal in both circuits at all times, and thus 

 cures the "kick." It is this quality of a con- 

 denser that enables us to give to an artificial 

 line of any resistance all the qualities, includ- 

 ing capacity, and exhibit all the phenomena 

 of a real line of any length, and it was this 

 quality that enabled Mr. Stearns to take the 

 " kick " out of duplex transmission and thus 

 change the whole system, which created a new 

 era in telegraphy. 



We have just spoken of the " capacity " of a 

 circuit, and stated that it was determined by 

 the mass of metal used. This capacity is meas- 

 ured by a standard of capacity that is arbi- 

 trary and consists of a condenser, constructed 

 so that a given amount of surface of tin-foil 

 may be plugged in or out. The practical unit 

 "f capacity is called the micro-farad, the real 

 unit is the farad, and takes its name from 

 Faraday. 



But let us go back to multiple systems of 

 transmission. There are many other systems 

 of Minultaneou> transmission aside from the 

 duplex, and all of them are classed under the 

 al head of multiple telegraphy. Fir-i 

 there is the quadruplex, that sends two mes- 

 sages each way simultaneously, making one 

 wire do the work of four single wires as 



