DISCOVERY 



13 



currents in the aerial, or may be placed in the valve 

 circuits, so as to modulate the currents at the source, 

 the energy in either case being transferred from the 

 valve circuits to the aerial bj' the currents in coil a, 

 inducing exactly similar currents in coil b. At the 

 receiving end (Fig. 3), the currents produced in the 

 aerial bv the wireless waves are exactly similar in 

 form to those in the sending aerial and flow through 

 coil c, inducing exactly similar currents in coil d, 

 which is connected to the valve receiving circuits in 

 which the telephone receiver is inserted. The aerial 

 in land and ship stations is supported by masts, and 

 in aircraft is let down as a trailing wire or is made up 

 as a coil in the aircraft itself. The " earth " consists 



wireless speech was first received from an aeroplane, 

 and there is no doubt that our Flying Corps was the 

 pioneer in this method of aircraft communication. 

 One of the first successful demonstrations of wireless 

 telephone working from aircraft in France was given 

 to Lord Kitchener at St. Omer. Unfortunately, 

 however, the messages from the aeroplane were heard 

 as far away as Lowestoft, and further experiments 

 were prohibited for quite a long time, as it was thought 

 that the enemy might obtain some valuable informa- 

 tion by reading our messages. 



In 1915 most pilots considered all wireless more as 

 a nuisance than anything else, whereas it has been 

 stated that in 1919 some pilots on the postal routes 



-SHIP AERI-AX. 



of metal plates or wires in the ground or water, or, 

 in the case of aircraft, metallic portions of the fusillage. 

 It was only a year or so before the outbreak of war 

 that experiments were commenced with wireless 

 telephony using the Three-Electrode Valve as a 

 transmitter, and during the war nearly all work 

 carried out in Europe on wireless telephony was 

 directed towards the development of small sets, 

 especially in connection with aircraft. This was 

 largely due to the fact that in aeroplanes the use of 

 wireless telegraphy entailed the pilot or observer 

 being trained as a telegraphist, and acting as such 

 in addition to his other duties, as it was usually im- 

 practicable to carry a wireless operator for wireless 

 duties only. Pilots and observers had plenty of other 

 work to get through, and the advantage of having a 

 simple telephone set which could be used with little 

 technical knowledge soon became very apparent. 

 It was in the summer of 1915 in this country that 



refused to go up without a wireless telephone. About 

 the time of the Armistice, aeroplanes were normally 

 communicating by wireless telephony with ground 

 stations up to about fifty miles, and with each other 

 up to about five miles, but these ranges have now been 

 more than doubled. 



In the United States, during the early part of the 

 war, more time could be spared for experiments with 

 larger sets, and spoken messages were heard at the 

 Eiffel Tower Station in Paris, about 2.300 miles, and 

 sometimes even at Honolulu, about 5,000 miles. 

 Since then other great distances have been accom- 

 plished, such as between this country and America, 

 but it must be understood that such long-range 

 working is still in the experimental stage, though its 

 realisation as a commercial proposition is no doubt 

 only a matter of time. There is no great technical 

 diffiiculty in linking up wireless telephony with line 

 telephony, to allow of the communication being partly 



