Masterpieces of Science 



near Calais, spoke to Wimereux by means of a 

 Marconi apparatus, with Cape Grisnez, a lofty 

 promontory, intervening. In ascertaining how 

 much the earth and the sea may obstruct the 

 waves of Hertz there is a broad and fruitful field 

 for investigation. "It may be," says Professor 



Fig. 73 Discontinuous electric waves 



John Trowbridge, "that such long electrical 

 waves roll around the surface of such obstruc- 

 tions very much as waves of sound and of water 

 would do. " 



It is singular how discoveries sometimes arrive 

 abreast of each other so as to render mutual aid, 

 or supply a pressing want almost as soon as it is 

 felt. The coherer in its present form is actuated 

 by waves of comparatively low frequency, 

 which rise from zero to full height in extremely 

 brief periods, and are separated by periods de- 

 cidedly longer (Fig. 73). What is needed is a 

 plan by which the waves may flow either con- 

 tinuously or so neat together that they may lend 

 themselves to attuning. Dr. Wehnelt, by an 

 extraordinary discovery, may, in all likelihood, 

 provide the lacking device in the form of his in- 

 terrupter, which breaks an electric circuit as often 

 as two thousand times a second. The means for 

 122 



