Inaugural Address by the President. 33 



If I have not wearied you too much I would now attempt to 

 show two or three rather interesting experiments with another 

 new electric invention. Wehnelt's electrolytic interrupter as 

 applied to the induction coil. 



The construction of the Wehnelt is very simple — merely a 

 jar containing dilute sulphuric acid into which dips a lead plate 

 forming the negative terminal of a supply at 100 volts or so. 

 The ether terminal is a platinum wire about the thickness of 

 a darning needle enclosed in a glass tube so as to expose only 

 half an inch or so to the liquid. When the current is switched 

 on it passes by the platinum wire through the liquid to the lead 

 plate. In doing so it heats the little platinum wire red hot. 

 The heated wire electrolyses and also boils the acidulated water 

 in contact with it, and surrounds itself with a layer of steam 

 and electrolysed gas. Steam being a non-conductor the 

 current cannot pass it, and so the needed interruption of the 

 current occurs. The steam then promptly condenses thus 

 allowing the dilute acid to come again in contact with the 

 platinum wire. The current again flows, only to be interrupted 

 again and so on at the rate of several hundred times per second, 

 the rate of frequency depending on the make of the interrupter, 

 and the self-induction of the coil employed. The result at the 

 secondary terminals is a torrent of sparks succeeding each other 

 so rapidly as to resemble a flame of fire. If the terminals be in 

 the form of circles placed one over the other the discharge 

 between them may be made to move round the circles by the 

 proximity of a magnetic pole according to well known laws 

 Again if the terminals be prolonged two or three feet in an 

 upward direction, but diverging slightly as they rise, the dis- 

 charge will form at the lower part, be carried up by the heated 

 air formed in its track till it breaks at the top to reform below. 



Sir Otto Jaffe, in moving a vote of thanks to the President, 

 said it would be an impertinence on his part to attempt to 

 criticise the lecture they had heard. He congratulated the 

 President in that he had not only attempted but had been 

 successful in scientific researches on one of the most difficult 

 subjects of the present day. 



