In a rapid and illuminating sketch of the early work done in electricity and magnetism the subtle and close connection between pure research and so-called industrial research is shown. Building on the work of Faraday, Maxwell and Hertz, Marconi, in our day, had the confidence to do the practical thing. From the Hertz oscillating system he passed to grounded antennas at both sending and receiving stations. From the well-understood tuning of electrical circuits and the coherer of Professor Branly he secured increased efficiency and selectivity. Mr. Edison, following the early work of J. J. Thomson at Cambridge University, England, devised the first practical application of the electron apparatus, the Edison relay. The vacuum tube became in the radio field an amplifier, an oscillator and a modulator, the audion. In addition to these interesting developments are the Poulsen arc, the Alexanderson alternator and other alternators of German design.
At the beginning of the war the foundations of the art of radio telephony had been laid. A transmitter responsive to speech sound waves but not to extraneous sounds has since been developed.
Concerning the future of radio telephony the author comments on the claims of enthusiasts who from their little knowledge are predicting impossible things. The air is needed for many purposes and cannot be claimed for the exclusive use of one. Aside from aeronautic practice, radio activity will probably be confined to use between ships at sea and ships and the shore, in new countries between stations separated by territory over which it is impossible to construct wire circuits, between land stations separated by long stretches of water and between land stations to insure continuous telephonic communication.
