118 



ANNUAL REPORT SMITHSONIAN INSTITUTION, 1911. 



The general principles on which practical radiotelegraphy is based 

 are now so well known that I need only refer to them in the briefest 

 possible manner. 



Wireless telegraphy, which was made possible by the fields of 

 research thrown open by the work of Faraday, Maxwell, and Hertz, is 

 operated by electric waves, which are created by alternating currents 

 of very high frequency, induced in suitably placed elevated wires or 

 capacity areas. These waves are received or picked up at a distant 

 station on other elevated conductors tuned to the period of the waves, 

 and the latter are revealed to our senses by means of appropriate 

 detectors. 



My original system as used in 1896 consisted of the arrangement 

 shown diagrammatically in figure 1, where an elevated or vertical wire 



was employed. 

 This wire some- 

 times terminated 

 in a capacity or 

 was connected to 

 earth through a 

 spark gap. 



By using an in- 

 duction coil o r 

 other source of 

 sufficiently high 

 tension electricity 

 sparks were made 

 to jump across the 

 gap; this gave rise 

 to oscillations of 

 high frequency in 

 the elevated conductor and earth, with the result that energy in the 

 form of electric waves was radiated through space. 



At the receiving station (fig. 2) these waves induced oscillatory 



currents in a conductor containing a detector, in the form of a coherer, 



which was usually placed between the elevated conductor and earth. 



Although this arrangement was extraordinarily efficient in regard 



to the radiation of electrical energy, it had numerous drawbacks. 



The electrical capacity of the system was very small, with the 

 result that the small amount of energy in the aerial was thrown into 

 space in an exceedingly short period of time. In other words, the 

 energy, instead of giving rise to a train of waves, was all dissipated 

 after only a few oscillations, and, consequently, anything approaching 

 good tuning between the transmitter and receiver was found to be 

 unobtainable in practice. 



Fig. 1. 



Fig. 2. 



