WIRELESS TELEGRAPHY 



your fist. These sparks, Hertz showed, have a 

 peculiar effect. They seem to set up waves in 

 every direction. 



The effect is, apparently, just like dropping a 

 stone in a still pond. Waves go radiating across 

 the water, and if you watch a cork floating on the 

 surface you will notice it bob up and down. If 

 you could not see the waves, the cork might make 

 them known to you. It is a wave-detector. If 

 you could send out long ripples and then short 

 ones, you might combine them in such a way 

 as to make the bobbings of the cork spell out 

 words. 



That is what Marconi does with the electric 

 waves. To one of the polished brass balls a wire 

 is attached, which runs up a high mast or hangs 

 from a kite. The electric pulsations set up when 

 a spark leaps from one ball to the other run along 

 the wire, and are thence radiated off into space. 

 Just how large a role this suspended wire plays 

 in the sending is not yet very clear. Maybe some 

 day it will not be needed. The sending instru- 

 ment might be located in the cellar, for these elec- 

 tric-waves seem to go through brick and stone, 

 and almost everything, save the metals. 



It is clear enough that if the sending operator 

 can open and close his circuit as he likes, he 

 make the series of sparks long or short as he 



