702 



Professor J. A. Fleming 



[May 24 



These waves travel through space, fall on the receiving antenna and 

 affect the resistance of the electrolytic detector in proportion to their 

 intensity. Hence the receiving telephone repeats the sounds or 

 articulations made against the transmitting microphone and reproduces 

 speech. The German experimentalists say that a satisfactory wireless 

 transmission of speech can be made in this manner, 20 kilometres or 

 12 miles over water with antennas 25 metres or about 80 feet high. 



Ruhmer has recently described in the Elelctroteclmische Zeitsckrift 

 some similar experiments made with a 220 volt Poulsen arc. In this 

 case the necessary modulation was impressed upon the radiated 

 electric waves by inserting the primary circuit of an induction coil 

 in the continuous current arc circuit, and closing its secondary 



R ° 





oN 



m/z/.w^'. 



t] 



Fig. 15.— Wireless Telephony by Electric Waves. 



through a microphone transmitter and working battery. The 

 receiving arrangement involved an electrolytic receiver as just 

 described. Professor Fessenden has recently described very similar 

 aiTangements for electric wave wireless telephony.* We can, hoAV- 

 ever, say that something more than a beginning has been made in 

 the art of the wireless ti'ansmission of human speech to a distance. 

 The energy expenditure is at present considerable, and mu(;h will 

 have to be done before telephony without wires can be looked upon 

 as coming within the range of connnercial work. Nevertheless, 

 having regard to the enormous impi'ovements in wireless telegraphy 

 in the last seven years it is quite within the bounds of possibility 

 we may soon be able to speak across the English (Channel without a 

 wire, and not scientifically impossible for the sounds of the; human 



See Tlie Electrician, vol. Iviii. p. 710, 1907. 



