402 Transactions. — Chemistry. 



this sparking across, as if every now and again the resistance to the passage 

 of the current from cither side was in a measure increased, and rather than 

 the whole of it would pass though the vacuum tube a portion preferred passing 

 direct. 



My first experiment in this direction resulted in some slight damage to 

 one of the coils (the condenser being destroyed), and on my second experiment 

 of the same nature, through the accident resulting from the first, I was not 

 inclined to prolong the experiment beyond being able to satisfy myself that 

 the current still continued to pass in the manner described in the first 

 experiment, when the receiving poles were joined to theii' respective spheres 

 at G and H. 



It will thus be seen from the foregoing description of the experiments 

 . above named, that there is some tangible ground for believing that the 

 currents in duplex telegraphy do pass one another. The subject yet, in my 

 opinion, requires further investigation before that point can be finally settled ; 

 possibly it may never be conclusively proved either one way or the other, or, 

 at any rate, not until such time as we are enabled to state what electricity 

 . itself is. Looking at it from a common-sense point of view, however, one 

 would naturally come to the conclusion that they must pass, or that the 

 currents, like two bodies meeting each other, exchange impulses, and thus 

 cause the opposite signal, or rather the will of each sender, to be transmitted 

 to its destination. 



The foregoing method in working duplex is on the open-circuit principle; 

 that is to say, the signal is made by sending the current to line (charging the 

 wire with electricity from the battery for the time being). 



It is possible, and perfectly practicable, however, to work duplex, in 

 accordance with the arrangement described, by the constant current, or closed 

 circuit, by making the following slight alterations in the manner of joining up. 

 The plan is as follows : — The battery is placed at the back connection of the 

 key, with the zinc current to line, and the resistance to balance the battery is 

 placed in the front contact, the earth connections being still maintained in 

 botli cases, as shown. The relays are placed so as to receive the opposite 

 current to that sent from the battery, and are so adjusted that when the 

 current is on the line (which will be when the key is at rest) the tongue of the 

 relay is held on the insulated stop by the current entering the relay, 

 weakening the magnetism on the side it enters, and strengthening tlie 

 magnetism on the side the insulated stop is on. As soon as the key is moved, 

 and contact made on the fi-ont anvil, through the current immediately leaving 

 the line, the opposite pole of the relay reasserts its sway and attracts tlio 

 tongue of tlic relay, and in doing so closes the local circuit, and thus records 

 the signal. 



