HERTZ, THE DISCOVERER OF ELECTRIC WAVES 337 



tools necessary for the really great advance that was ahead. With 

 the invention and development of the amplifying and oscillating 

 vacuum tube progress was greatly accelerated, and in a comparatively 

 short time there had been achieved, by a veritable army of experi- 

 menters, the marvels of world-wide intercommunication which are so 

 familiar to us today. 



