RECENT ELECTRICAL DISCOVERIES 119 



ing wireless telegraph messages. The device consists 

 of a glass globe about ten inches in diameter, hav- 

 ing two tubes containing mercury sealed in the 

 bottom of the vessel. 



This apparatus acts as a powerful and effective 

 interrupter and takes the place of the spark gap 

 now used in discharging the condensers for setting 

 up electrical waves. It enables powerful, rapid and 

 continuous oscillations to be set up in the antenna, 

 or sending mast, used in transmitting wireless mes- 

 sages, and not only enables messages to be sent 

 over very great distances with ease, but permits 

 secrecy to be maintained, which heretofore has 

 been impossible. 



The operation of this device depends upon two 

 new phenomena in physics which Mr. Hewitt has 

 discovered in the course of his researches. The 

 first is the resistance of the mercury in the appa- 

 ratus to a passage of current until a high potential 

 has been applied; the second is the disappearance 

 of this resistance after this high voltage has been 

 reached. 



The effect of these two phenomena is to permit 

 a condenser to be charged to a high potential and 

 then, by the disappearance of the resistance of the 

 interrupter, to discharge it very rapidly. The result 

 of this action is to set up violent and rapid current 

 impulses in the circuit containing the condenser, and 

 thence in the sending wire. The current impulse, 

 being very powerful, will enable messages to be 

 sent to great distances, and as the number of oscil- 

 lations per second can be controlled, this permits 

 of selective signaling. The number of impulses can 

 l?e made very high above a million a second. The 



