706 



Professor J. A. Fleming 



[May 24, 



fine wire (see Fig. 19). When a s^alvanometer of suitable resistance 

 is connected to the terminals of the thermo-junction and the con- 

 stantin wire inserted in the circuit of the receiving antenna we have 

 an arrangement which enables us to measure as well as detect the 

 intensity of the electric waves incident on the antenna. This de- 

 tector, skilfully made bv my assistant, Mr. Dyke, proved very useful. 

 I was thus able to confirm Mr. Marconi's observations and my own 

 theory of them, and furthermore noticed that when the non-vertical 

 part of the transmitting antenna was bent so that it was not hori- 

 zontal but pointed downwards, a very remarkable non-symmetry of 

 radiation occurred, quite, however, accounted for by theory (see 

 Fig. 20). Mr. Marconi has made very effective practical use of the 

 bent receiving antenna to locate the position of a ship or station 



Fig. 19. — Thermal Detector. 



sending out electric-wave messages when so far off as to be below 

 the horizon. 



In this case he arranges the receiving antenna so tliat a> very 

 short part is vertical and the greater part liorizontal, and furthermore 

 permits the horizontal part to be swivelled round tlie vertical part as 

 a centre. In the vertical portion he places his magnetic or some 

 other detector. If then there l)e a distant station in corivspondence 

 with this receiver, tlie direction in wliicli tlie transmitter lies can be 

 determined witliin a few degrees by swiveUing round tlic reeciving 

 antenna, and noting tlie ])osition in which \l picks up signals or picks 

 them up best from this transmittei". The transmitter then lies in the 

 direction o])posite to that in which the free end of the receiver wire 

 points. If it is not convenient to swivel round the horizontal portion. 



