1907.] on Recmt Contrihutmis to Electric Wave Telegraphy. 607 



the small electrode and liquid in its neighbourhood. In any case, 

 the action is just as if the resistance of the electrolytic cell were 

 suddenly changed, either increased or decreased. It has also been 

 found by Rothmund and Lessing that the cell may be made to supply 

 its own electromotive force. If we form a simple polarisable voltaic 

 cell with fine zinc and platinum wires immersed in dilute acid and 

 connect a telephone or high resistance galvanometer to these elements ; 

 then, when electric oscillations pass through the cell, the current sent 

 by it through the telephone or galvanometer is momentarily increased. 

 That the action is not altogether due to the removal of polarisation 

 films is shown by the fact that the fine platinum wire in the 

 Schloemilch form of detector wears away or is dissolved in the nitric 



Fig. 13. — Oscillation Valve (Fleming). 



acid when oscillations are passed for some time through the cell, and 

 there is some evidence that gold and platinum can be made to dissolve 

 even in dilute acids by the action of electric oscillations. 



In 1904 I was so fortunate as to discover another and quite 

 different principle on which a sensitive electric wave detector can be 

 based. If a carbon filament glow lamp has a metal plate carried on a 

 third terminal sealed into the bulb, it is well known that a current of 

 negative electricity flows from the plate to the positive terminal of the 

 lamp, when the filament is rendered incandescent by a continuous 

 current. This is the so-called Edison effect. It is also now known 

 that incandescent bodies discharge negative corpuscles or electrons 

 from their surface, and incandescent carbon, when in a vacuum. 



